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US Army Corps of Engineers ^ \XyCVt ^»^*- •< GEOMORPHOLOGY AND QUATERNARY GEOLOGIC HISTORY OF THE LOWER MISSISSIPPI VALLEY Prepared by Roger T. Saucier U.S. Army Engineer Waterways Experiment Station Vicksburg, Mississippi December 1994 Volume '" i § t L « C < w — f e S E P 9 9 5 j s > > Prepared for: The President Mississippi River Commission Vicksburg, Mississippi DISTRIBUTION STATE»fX Approved or public eleases- Distribution Unlimited 19950907 0 1
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S E P 9 9 5 j
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Approved or public eleases-
The contents of this report are not to be used for advertising,
publication, or promotional purposes. Citation of trade names
does not constitute an official endorsement or approval of th e us e
of such commercial products.
Prepared by Roger T. Saucier
U.S. Army Corps of Engineers
Waterways Exper iment Station
3909 Halls Ferry Road
Prepared fo r T he President
Mississippi iver Commission
Vicksburg, MS 39181-0080
Definitions
Holocene meander belts and distributaries
Deltaic and Chenier Plain Segments 9
Uplands, distributary ridges, nd cheniers 9
Interdistributary lowlands and basins
Continental Glaciations 6
Glacial response model
Effects of sea level change 6
Reconstructing sea level history
Tectonics and Diapirism
-Landfonns and Geomorphic Processes 9
Erosional Landscapes
Stream entrenchment
Upland graveliferous deposits
Lacustrine Environments 2 9
Prodelta deposits
Pimple mounds 6 2
Pleistocene Terrace Complexes
Interdistributary 04
"Eowisconsin" Stage Events nd Deposits 3
Background 2 2 3
Late Wisconsin Stage Valley Entrenchment
Mississippi River Meander Belts
Stage 2 6 6
White/Black River Lowland
R ed River Meander Belts
Lafourche 2 82
L a n d doming an d inking 9 5
Landsliding and bank caving 9 6
Faults nd lineaments 9 8
Faulting and Regional Fracturing 01
Mississippi Valley area
Groundwater Occurrence 06
Mass Movements 09
Landsliding 12
References 3 4
Appendix B : Index
plain, nd th e total distribution of Quaternary deposits in
th e Lower Mississippi Valley portion of th e Gulf Coasta l
Plain
from Weinstein et al . 1979) 17
Figure 3 . Standard geologic column applicable to the Lower
Mississippi Valley area 3 3
Figure 4. Geologic column fo r the Quaternary period showing
conceptual stages nd a generalized sea level curve
indicating eustatic cycles (modified from Beard, Sangree,
and Smith 1982)
40
Figure 5 . History of post-Illinoian sea level variations in the Gulf
C o a s t area (dashed lines indicate interpretations by the
author) (adapted from Revelle 1983, Goodwin et al . 1991,
and other sources)
Figure 6. Major structural features of the Lower Mississippi Valley
(modified from Autin et al . 1991)
Figure 7. Comparative interpretations of th e configuration of the
entrenched uballuvial surface in a portion (Mossy L a k e
quadrangle) of the Yazoo Basin of west-central Mississippi
(from Kolb et al . 1968, and subsequent revised editions) .. 75
Figure 8. Alluvial fans. A: Small, discrete, symmetrical fa n of
unnamed creek near Leverett in Tallahatchie Co., M S
(Plate 8); B : Coalesced, smal l fans forming alluvial
apron (in cultivation) west of U . S . Highway 61 near
Yokena in Warren Co., M S Plate 9 )
Figure 9 . Configurations of and channel patterns on three alluvial
fans representing a range of types and sizes: A=Teoc
and (B ) Late Wisconsin valley train in D ee quadrangle,
Poinsett Co., AR (adapted from Whitworth 1988,
Saucier 1964)
9 5
Figure 11. Relict braided channel patterns on valley trains. A: Early
Wisconsin-age channels near Weiner in Poinsett Co., AR
(Plate 6) marked by entrenched local drainage; B : a te
Wisconsin-age elict channel east of Crowley's Ridge near
Harrisonburg in Poinsett Co., AR (Plate ) marked only by
darker soil tones (between arrows) 9 6
Figure 12 . A ypical meander belt ridge (A) within th e context of th e
Mississippi lluvial valley (modified from Fisk 1947) and
an illustration (B ) of the principal depositional environ-
ments involved modified from Allen 1964) 10 0
Figure 13 . Primary and econdary depositional environments and
related channel features of a typical meander belt (from
Gagliano nd va n Beek 1970)
Figure 14. Natural levees. A: Natural levee, clearly evident by
distribution of cultivated fields and hardwood forest
vegetation (between arrows), along the Mississippi River
near Gramercy in St. James Ph., L A (Plate 12); B : Crevasse
channels (marked by arrows) on natural levee flanking L a k e
Providence, n abandoned channel in E a s t Carroll Ph., L A
(Plate 9 )
Figure 15 . Crevasse splays. A: Anastomosing channels from large,
natural crevasse that formed along th e south side of False
River in Pointe Coupee, Ph., L A (Plate 11) when it was the
active course of the river; B : Crevasse splay esulting
from failure of an artificial levee (Morganza Crevasse of
April 1890) near Morganza in Pointe Coupee Ph., L A 10 4
VIM
Figure 16 . Distributaries. : bandoned channel and natural levees
(cultivated reas) of th e D e e r Creek distributary near Valley
Park in Issaquena Co., MS Plate 9); B : ain channel and
branches of th e River distributary near
Walters in Catahoula Ph., L A (Plate 10) 10 6
Figure 17 . T wo large distributary systems originating from crevasses
along Arkansas River meander belts northeast of Monroe
in northeastern Louisiana (from Kidder and Saucier 1991)
(meander belt details and traces of older meander belts
omitted to avoid confusion) 108
Figure 18. Point bar environment. A: Sand waves being deposited on
an actively accreting point bar along the Chute of Island
N o. 5 bend of th e Mississippi River in Tipton Co., T N
(Plate 6); B : oint ba r ridges and swales of on e meander
sequence truncating another east of th e Tensas River near
Ferriday in Concordia Ph., L A Plate
Figure 19 . Point ba r environment. A: Complex accretion topography
indicating movements of several different Mississippi River
bends west of St. Francisville in West Feliciana Ph., L A
(Plate 11); B : oint bar ridges and swales veneered with
natural levee deposits near th e present river channel at
Duncan Point south of Baton Rouge in E a s t Baton Rouge
Ph., L A (Plate 11)
HI
Figure 2 0. haracteristic stages in th e life cycle of a typical neck
cutoff along a major stream in th e Mississippi lluvial
vaUey 114
Figure 2 1. Abandoned channels. A: Cocodrie L a k e north of Monterey
in Concordia Ph., L A (Plate 10), a classic-shaped Missis-
sippi River cutoff with oxbow lake and filling of arms
below point of cutoff; B : Smal l batture channel connect-
in g oxbow lake near Raccourci O ld River in Pointe Coupee
Ph., L A (Plate 11) with Mississippi River (channel filling
located between arrows deposited between 1848, date of
cutoff, and 1959, date of photo) 115
Figure 2 2 . Abandoned channels. : ypical batture channel pattern
as exemplified by T he Chenal in th e lower arm of th e False
River cutoff in Pointe Coupee Ph., L A Plate 11) (aban-
doned channel limits indicated by arrows); B : Essentially
filled abandoned channel characterized by s w a m p forest
vegetation west of Centennial Island in Crittenden Co.,
AR (Plate 6)
detectable by characteristic vegetation assemblage
and soils (between arrows) along the Tensas River
northeast of Sicily Island in Tensas Ph., L A
(Plate 10); B : Abandoned channel southwest of Hughes
IX
in L ee Co., AR (Plate 7) sufficiently filled and
well drained to allow agriculture limits located
between arrows detectable by absence of point bar
ridges nd wales, vegetation, nd darker soil tones) 118
Figure 2 4. Abandoned courses. A: Mississippi River abandoned
course now occupied by th e Tensas River southeast of
Sicily Island n Tensas Ph., L A (Plate 10), estimated
channel bank lines indicated by arrows);
B : Underfit streams Hopson and Cassidy bayous) that
have exceeded and largely obliterated th e limits of
th e former Mississippi River course northeast of
Tutwiler in Quitman and Tallahatchie Cos., MS Plate 7) 12 0
Figure 2 5 . Configurations of Mississippi River meander belts as
defined by the extent of the point ba r environment (A),
and distribution of neck and chute cutoffs (B ) 12 2
Figure 2 6 . Backswamp. A: Nearly featureless, forested backswamp
tract in the Atchafalaya Basin south of Lottie in
Pointe Coupee Ph., L A Plate 11); B : R im swamp in the
Spanish Lake rea south of Baton Rouge at th e junction
of Ascension, E a s t Baton Rouge, nd Iberville parishes,
L A Plate 11) (cultivated areas lie on the Prairie
Complex, nd th e Mississippi River meander belt lies to
th e west beyond the limits of the photo) 12 8
Figure 2 7. Sand dunes. A: Well-defined tract of sand dunes
(between arrows) between braided channels south of
Naylor in Ripley Co., M O Plate 5) some large depres-
sions between dunes still orested); B : More intensely
cultivated nd subdued bu t still visible dunes (lighter
soil tones) nd depressions darker soil tones) north-
west of Walnut Ridge n Lawrence Co., AR Plate 5) 13 5
Figure 2 8. Idealized urface nd ubsurface distribution of environ-
ments of deposition t several stages in a typical delta
cycle (from Frazier and Osanik 1965)
Figure 2 9 . Block diagram showing relationships of subaerial nd
subaqueous deltaic environmenls of deposition in a
single delta lobe from Coleman and Roberts 1991) 13 9
Figure 3 0. Hypothetical edimentary sequence resulting from everal
overlapping deltaic cycles showing major environments of
deposition (from Coleman and Gagliano 964) 140
Figure 3 1. Highly popular, bu t outdated, nterpretation of
Holocene delta complexes A) , nd currently
accepted nterpretation (B )
Figure 3 2 . Distributaries. A: Bayou Lafourche, a major Mississippi
River distributary in Terrebonne Ph., L A (Plate 14) marked
by well developed natural levees cleared fo r agriculture;
B : mall distributaries in southern Terrebonne Ph., L A
(arrows) indicated by conspicuous relict channels but
whose subsided natural levees are barely discernible by
slight vegetation differences (shrubs) from adjacent marsh 14 2
Figure 3 3 . Inland swamp. : early featureless inland swamp south-
west of L a k e Maurepas in Ascension Ph., L A (Plate 12 )
(linear features are abandoned railroad spurs used in
cypress logging operations in th e early 20th century);
B : nland s w a m p in a more-coastal setting, interrupted
by areas of freshwater marsh (lighter tones), near
Calumet in St. Mary Parish, L A (Plate 13 ) 144
Figure 3 4. Intratidal marsh. : rackish marsh east of L a k e Borgne
in St. Bernard Ph., L A (Plate 14) characterized predominantly
by three-cornered grass (Scirpus olneyi); B: Well-drained
salt marsh along Mississippi Sound in St. Bernard Ph., L A
(Plate 12 ) composed mainly of black rush (Juncus
roemerianus) and wiregrass (Spartina patens) 146
Figure 3 5. Intratidal marsh. A: Freshwater marsh, dominated by
cattail (Typha spp.) and roseau cane {Phragmites
communis), created after 1891 a crevasse splay in
Garden Island B ay in Plaquemines Ph., L A (Plate 14);
B : Nearly uninterrupted tract of floating fresh marsh
west of L a k e Salvador in Lafourche Ph., L A (Plate 14)
(tonal patterns on marsh caused by episodes of deliberate
burning to enhance marsh productivity)
14 8
Figure 3 6 . Model showing the distribution of environments at several
transgressive stages in a deteriorating delta lobe (from
Penland and Boyd 1981) 15 2
Figure 3 7. Beaches and barriers. : rosional headland in th e Isles
Derniers area of southern Terrebonne Ph., L A Plate 14)
(intratidal marshes represent surviving portions of th e
delta complex); Portion of a flanking
barrier island of the Isles Derniers chain 15 4
Figure 3 8. Reefs. xtensive oyster reefs extending southward
into th e Gulf of Mexico from Marsh Island in Iberia
Ph., L A (Plate 13 )
Figure 3 9 . Cheniers. runcated series of relict beaches, indicating
former Gulf shorelines, fomring Pecan Island, a large
chenier in Vermilion Ph., L A (Plate 13 ) 15 8
Figure 40. Model of chenier development showing surface physiog-
raphy and subsurface sedimentary facies (from Gould
and McFarlan 1959) 16 0
XI
mounds on silty clay soils (Early Wisconsin valley
train deposits) east of Bald Knob in White Co., AR
(Plate 6 ); B: imple mounds of moderate size and
density on sandy loam soils (Early Wisconsin valley
train deposits) southwest of Naylor in Ripley Co.,
M O (Plate 5) 16 3
Figure 42 . Sand blows and fissures. : Dense scatter of relatively
undisturbed sand blows on Late Wisconsin valley train
deposits near Rivervale in Poinsett Co., AR (Plate 6);
B : Sand blows and fissures well diffused by cultivation
on Late Wisconsin valley train deposits southeast of
Lepanto in Poinsett Co., AR (Plate 6 )
near-surface portions of the Prairie Complex 17 4
Figure 44. Model showing the distribution of subenvironments nd
deposits of a typical valley train during early (A )
and late (B ) phases of outwash deposition during
waning glaciation (from Whitworth 1988) 184
Figure Longitudinal slope, width, thickness, nd general
composition (soil type frequency diagram) of natural
levee deposits from near Donaldsonville (Plate 11) to
near Fort Jackson, L A (Plate 14) from Kolb 1962) 19 0
Figure 46 . Diagrammatic cross section of a meander belt showing
typical distribution of deposits and sedimentary struc-
tures in a point ba r sequence (from Gagliano and
va n Beek 1970) 19 2
Figure 47. Locations and early interpretations of the ages of fluvial
and marine features of th e Prairie Complex in southwestern
and outheastern Louisiana (from Saucier 1977b) 4
Figure 48 . Configuration of th e entrenched surface (first horizon) on
Wisconsin-age deposits of the Prairie Complex as mapped
on th e N ew Orleans E a s t and Spanish Fort 1:24,000-scale
quadrangles 2 3 8
Figure 49A. onfiguration of th e to p of the western half of the
Holocene-age Pine Island Beach Trend buried beneath
deltaic deposits in th e greater N ew Orleans area 1
Figure 4 9 B . onfiguration of the top of the eastern half of the
Holocene-age Pine Island Beach Trend buried beneath
deltaic deposits in th e greater N ew Orleans area 2
Figure 50. stimates of ages of channel tages (meander belts) of
major rivers, delta complexes, nd cheniers; modified
from Autin et al . 1991) 5
XI I
Figure 5 1. Evolution of a part of th e Yazoo Meander Belt (Stage 2 )
as reconstructed using geomorphological and archeological
evidence from th Teoc Creek and Neill Sites (modified
from Connaway, McGahey, nd Webb 1977) 5
Figure 5 2 . Major structural features of the N ew Madrid Seismic Zone
along with epicenters of microearthquakes (modified from
Luzietti et al . 1992)
Figure 53 . Distribution of liquefaction features (sand blows and
fissures) in th e N ew Madrid Seismic Zone (density classi-
fication based on estimated percentage of ground surface
covered by extruded sand prior to widespread disturbance
by agriculture) 9 2
Figure 5 4. Typical characteristics of liquefaction features in th e
N ew Madrid Seismic Zone as revealed along banks of
drainage ditches (modified from Wesnousky &
Leffler 1992) 2 9 3
Figure 5 5 . Known and inferred faults and major lineaments in the
N ew Madrid Seismic Zone (compiled from Crone 1992 ;
Heyl and McKeown 1988; Schweig, Marple, and L i 1992 ;
Zoback et al . 1980)
3 00
Figure 5 6 . Typical bank failure mechanisms in various alluvial and
deltaic environments of deposition (from Tumbull,
Krinitzsky, and Weaver 1966) 3 10
Figure Al. Geotechnical characteristics of shallow Pleistocene
deposits from beneath th e deltaic plain A3
Figure A2 . Geotechnical characteristics of Wisconsin-Stage braided
stream valley train) interfluve deposits
deposits of th e alluvial valley
deposits of th e alluvial valley
distributary deposits of the deltaic plain
distributary deposits of the deltaic plain
of the deltaic plain ll
XIII
Figure A10. eotechnical characteristics of Holocene s w a m p deposits
(backswamp and s w a m p environments)
of the deltaic plain 12
Figure All. eotechnical characteristics of Holocene prodelta deposits
of the deltaic plain 13
Figure A12. eotechnical characteristics of Holocene intradelta
deposits of th e deltaic plain 14
Figure A 1 3 . omparison of water content test data from various
and Holocene fluvial and
Figure A14. omparison of liquid limit test data from various
Pleistocene and Holocene fluvial and deltaic
environments 16
Figure A15. omparison of plastic limit test data from various
Pleistocene and Holocene fluvial and deltaic
environments 17
Figure A16. omparison of plasticity index test data from various
Pleistocene and Holocene luvial nd deltaic
environments 18
Figure A17. omparison of dry density test data from various
Pleistocene and Holocene fluvial and deltaic
environments 19
Figure A18. omparison of wet density test data from various
Pleistocene and Holocene fluvial and deltaic
environments 0
Figure A19. omparison of cohesive strength test data from various
Pleistocene and Holocene fluvial and deltaic
environments 2 1
Figure A20. omparison of blow count test data from various
Pleistocene and Holocene fluvial an d deltaic
environments 2
Figure A21. omparison of D 10 grain ize test data from various
Pleistocene and Holocene fluvial environments 2 3
List of Tables
Glacial/Interglacial Cycle in the Lower Mississippi
Valley (from Autin et al. 991) 3 8
Table 2 . Generalized, Composite Stratigraphic Column fo r th e
Lower Mississippi Valley 5 6
X IV
of Various Geologic Units in Louisiana (from
Autin et al. 1991) 171
Table 4. Occurrence of Minor Sedimentary Structures in Holocene
Fluvial Depositional Environments
Deltaic Depositional Environments
Marine Depositional Environments
Preface
In M ay 1941, th e U . S . Army Corps of Engineers, Mississippi River C o m -
mission ( M R C ) , Vicksburg, Mississippi, hired D r. Harold N . Fisk of Louisiana
State University, Baton Rouge, Louisiana, s a geological consultant nd
him to prepare comprehensive summary of th e geology of th e Lower
Mississippi Valley. T he resultant product, Geological Investigation of the
Alluvial Valley of the Lower Mississippi River, was published by th e M R C in
December 1944 nd oo n became the authoritative reference in th e field nd
eventually a classic.
Although m a n y of th e concepts and interpretations set forth in 1944 have
stood th e test of time, others have no t as ne w tools and techniques have
emerged, new hypotheses have been offered and tested, and geological
knowledge in general ha s advanced dramatically. o eflect th e advances of
th e past 50 years, which include a voluminous but dispersed literature, huge
amounts of new and sometimes unpublished data, nd evolving concepts of
valley history and chronology, th e M R C agreed in October 1992 to sponsor th e
preparation of a new, comprehensive geological and geomorphological
synthesis.
T he synthesis was prepared between October 1992 and December 1994 by
D r. Roger T . Saucier while assigned part time as a Physical Scientist to th e
Earthquake Engineering and Geosciences Division ( E E G D ) , Geotechnical
Laboratory (GL), U . S . Army Engineer Waterways Experiment Station (WES),
Vicksburg, Mississippi. General administration of th e project wa s provided by
Messrs. Frank Weaver, Lawrence Cave, nd Tony Y o u n g of the Geotechnical
and Materials Division, U . S . Army Engineer Division, Lower Mississippi Val-
ley L M V D ) , Vicksburg, Mississippi. Funds were provided by th e U . S . Army
Engineer Districts, Vicksburg, N ew Orleans, nd Memphis, t th e direction of
th e M R C .
D r. Saucier wa s uniquely qualified to prepare th e synthesis s a conse-
quence of his more than 3 5 years of detailed mapping and investigation of
multiple aspects of th e engineering geology of the Lower Mississippi Valley
while employed t W E S nd ls o serving as a private consultant. He ha s
authored th e only tw o limited ttempts of the last 50 years to summarize
aspects of th e geology of th e area, nd his research focus, reflected n dozens
of publications, ha s been on interdisciplinary considerations and pplications
X V I
ranging from rcheology to paleoseismology. D r. Saucier assembled and
reviewed th e literature for this synthesis, developed the outline and wrote th e
text, nd prepared most of the figures and plates.
Technical guidance, consultation, critical review, and ssistance in many
aspects of th e project were provided by D r. Lawson Smith of the E E G D ,
W E S , who also envisioned the need for the synthesis and served as a pro-
ponent of the project. Substantial assistance wa s provided by others in prepar-
in g tw o parts of th e synthesis. Messrs. T im Ethridge ( L M V D ) , Mike Bishop
(WES contractor), and William Murphy ( E E G D ) assembled and digitized the
data and implemented the computer contouring of the suballuvial surface and
prepared the graphical output. Mr. Ken Stroud, graduate student at th e Univer-
sity of Southern Mississippi, conducted under contract to W E S th e assembly,
evaluation, tatistical analysis, nd portrayal of th e data on th e geotechnical
characteristics (Appendix A). Drafting and scientific illustration associated
with th e numerous figures and plates were accomplished by and under the
direction of Messrs. William Park and Alan Middleton of the W E S Visual
Production Center, Information Technology Laboratory.
Peer review of th e manuscript wa s provided by D r. Whitney Autin of the
Institute for Environmental Studies, Louisiana State University, and D r. L a w -
son Smith and Mr. Joseph Dunbar, E E G D , W E S .
T he project was accomplished under the general supervision of Mr. Jo e L .
Gate, Chief, Engineering Geology Branch, E E G D , D r. A.G. Franklin, Chief,
E E G D , and D r. W.F. Marcuson III, Director, GL , W E S .
At th e time of publication of this report, Director of W E S wa s D r. Robert
W . Whalin. C o m m a n d e r wa s C O L Bruce K. Howard, E N .
Th e contents of this report ar e no t to be used for advertising, publication,
or promotional purposes. itation of trade names does no t constitute an
official endorsement or approval of the use of such commercial products.
XVII
Conversion Factors, Non-SI to
SI Units of Measurement
N o n - S l units of measurement used n this report ca n be converted to SI units
as follows:
gallons (U.S. iquid)
1 Introduction
Previous Investigations
With th e possible sole exception of th e insightful work of Lyell (1847), th e
earliest geological studies in the Lower Mississippi Valley area that reflect
reasonably modem concepts generally date between th e 1860s and th e early
1900s. hey include such notable works as those by Harris (1894) in Arkan-
sas; Hilgard (1860) in Mississippi; and Stubbs (1892), and
Veatch (1906) in Louisiana; Safford (1869) in Tennessee; nd Swallow (1877)
in Missouri. Emphasis in these publications was on agriculture and mineral
resources, but they also included descriptions of outcrops, springs, nd special
features nd devoted considerable attention to groundwater. Without question,
th e focus was on th e pre-Quaternary uplands. his reflects trend that was to
diminish but not disappear for m a n y decades, i.e., geologists were interested in
th e uplands and "hard rock" and not alluvium. he only significant exceptions
were studies by Marbut (1902) of the lowlands of southeastern Missouri nd
by Stephenson and Crider (1916) of a portion of northeastern Arkansas.
Fundamental aspects of th e geology of the alluvial valley, such as th e pres-
ence of glacial outwash (valley trains), multiple Mississippi River meander
belts, nd effects of sea level variations, were well known by th e beginning of
th e 20th century. However, they were not comprehensively or systematically
described by geologists during these early years. Soil scientists were actually
th e first to devote serious attention to the alluvial plain, and by the 1920s,
there were published soil surveys fo r a number of counties in Arkansas, Loui-
siana, Mississippi, and Missouri. These constitute th e first rather large-scale
maps of Quaternary physiography and surficial deposits.
A major turning point in th e documentation of Mississippi Valley
Quaternary geology occurred in th e early 1930s when th e Louisiana Geological
Survey initiated a series of truly comprehensive, large-scale, geological bulle-
tins covering parishes in the southern part of that state (e.g., Howe and Moresi
1931, 1933) . This series wa s later extended into central Louisiana (Chawner
1 9 3 6 ) and also marks th e first involvement of Fisk (1938) in Lower Missis-
sippi Valley geology. T he series focused on mineral resources (oil, gas, salt,
and sulphur), nd the first parish selected (Iberia) wa s because of its economi-
cally important salt domes. Nevertheless, th e bulletins provided n
Chapte r Introduction
unprecedented wealth of information on th e Quaternary of th e Mississippi
Valley. During th e decade of the 1930s, other states such as Mississippi nd
Tennessee initiated similar series bu t did not include counties in th e alluvial
valley area.
Prior to th e 1930s , geological studies in th e Lower Mississippi Valley area
were largely descriptive, concentrating on outcrops, physiographic features, and
stratigraphic correlations. In terms of alluvial and deltaic deposits, little atten-
tion ha been devoted to relating them to geomorphic processes and explaining
their origin and variability. Relatively fe w borings ha d been drilled; hence th e
nature of th e subsurface beneath the alluvial plain wa s largely unknown. Con-
sequently, geological knowledge wa s of limited utility to engineers who were
concerned with siting dams, designing levees, employing river regulation, nd
similar activities.
Another major turning point occurred n the early 1940s when the Missis-
sippi River Commiss ion ( M R C ) retained Harold N . Fisk, a geologist at Louisi-
ana State University ( L S U ) , s a consultant. Between 1941 nd 1948, Fisk
and a team of graduate students prepared 3 0 special geological reports fo r th e
M R C on such topics as bank erosion, levee underseepage, faulting, and lluvial
deposits and landforms, nd geologic studies of proposed lock and da m ites
and other structures n Louisiana, Arkansas, Mississippi, and Texas . Most of
these eports were never published; however, during th e eight-year period, Fisk
did publish tw o monographs (Fisk 1944, 1947) of valley-wide scope that were
to soon become widely known and used, nd eventually to achieve the status
of geological classics. These tw o works marked the beginning of engineering
geology in th e Lower Mississippi Valley.
Fisk's bility to relate the origin, distribution, and characteristics of deposits
to fluvial, deltaic, nd marine processes, nd hence develop a predictive capa-
bility fo r engineers, was largely attributable to tw o significant developments.
First, he wa s able to ake advantage of the first complete coverage of the
Lower Mississippi Valley by large-scale, vertical, erial photography that was
obtained by the U . S . Soil Conservation Service in th e late 1930s. Second, he
wa s able to obtain samples and logs from large number of strategically
placed, carefully drilled, nd logged borings that penetrated the lluvial
sequence. Those borings provided the first truly three-dimensional look t the
deposits of th e alluvial valley and deltaic plain.
During th e decades of the 1950s and 1960s, here wa s a virtual explosion of
th e volume of geological knowledge, ncluding that of direct relevance to
engineering practice. Thousands of site-specific s well as topical studies were
accomplished nd published se e bibliography of Saucier 1966), covering virtu-
ally al l fields of modem geology such as geomorphology, edimentology,
tectonics, eismology, paleontology, stratigraphy, nd chronology. Major
advances in knowledge resulted not only by the greatly increased interest and
efforts by academia an d government bu t also from the dvent of new tools nd
techniques. Paramount among these are geophysics, adiocarbon dating, nd
remote sensing.
U p o n th e departure of Harold Fisk from L S U in 1948 to Humble O il &
Refining Company) , th e focal point for specific engineering geologic investiga-
tions of th e Lower Mississippi Valley, and the continuation of this tradition,
shifted to th e Geology Branch of the U . S . Army Engineer Waterways Experi-
ment ( W E S ) in Vicksburg, Mississippi. Between that date and the present,
hundreds of geological studies of project sites and particular problems have
been conducted. owever, perhaps th e most important contribution wa th e
systematic large-scale (1:62,500) mapping of geomorphic surfaces and subsur-
face soils conditions and the inferred environments of deposition fo r essentially
a ll of th e Mississippi alluvial valley and ts major tributaries within the juris-
diction of th e U . S . Army Engineer Division, Lower Mississippi Valley. ight
folios of maps and cross sections, each covering a major basin area, have been
published in limited editions (Fleetwood 1969 ; Kolb et al . 1968; M ay et al .
1984; Saucier 1964, 1967, 1969 ; Smith and Saucier 1971; Smith and R u s s
1974) for us e primarily by th e U . S . Army Corps of Engineers.
Geological studies in th e decade of th e 1970s and continuing to date have
been more precisely focused on particular problem areas and locations and
much more sophisticated in approach. wo trends are evident. irst, there ha s
been a definite reach-out fo r additional tools and knowledge from related disci-
plines such as archeology, botany, chemistry, pedology, climatology, and
oceanography. hi s ha s been necessary not only to resolve problems in chro-
nology and paleoenvironmental reconstructions bu t also to better understand
processes affecting th e development of th e area. Second, it ha s been possible
to go beyond simple knowledge expansion to needed efforts in synthesis and
reanalysis, reinterpretation, and revision.
Because of th e intent of th e present volume, attention is directed toward th e
status of efforts at summarization and synthesis rather than specific investiga-
tions. Since th e first comprehensive look at the entire Lower Mississippi Val-
ley by Fisk (1944), there have been only tw o attempts to give engineers a
single source fo r an overview of th e geology of th e whole area with a discus-
sion of th e latest concepts. A brief summary of th e Quaternary geology of th e
valley wa s prepared in th e mid-1970s (Saucier 1974); however, it was intended
primarily for cultural resources managers. I t contained a new generalized
geologic m ap (approximate scale 1:1,250,000), a discussion of problems with
concepts, and the chronology of Fisk (1944), bu t it did not offer solutions. A
more comprehensive overview of the Quaternary geology of th e valley area,
including a moderately detailed, full color, geologic m ap (scale 1:1,100,000),
was published in 1991 Autin et al . 1991). hi s work, the most definitive
since 1944, provides th e most up-to-date discussions of new concepts of valley
origin and history, including a substantially revised chronology of events. I t is
balanced in scope and approach and intended for a general geology audience.
A primary attribute is its widespread availability~a major benefit in view of
th e limited vailability of the earlier work because of its rather obscure source.
Chapte r Introduction
Assessment of State of the Art
T he latest synthesis of Lower Mississippi Valley geology (Autin et al .
1991) is modest in scope and ha s not been available very long. Therefore, th e
classic 1944 tudy by Fisk is still th e most widely known, if no t widely
accepted, work of its type. espite its age and the fact that m a n y geologists
recognize it ha s significant shortcomings, th e 1944 work retains its appreciable
status several reasons, especially among engineers. several decades it
was the only reference of its type available, it is comprehensive in scope, nd
it wa s for its vintage) magnificent in execution. I t consists of tw o volumes:
a volume primarily of text, and a pocket of 2 6 large, multicolored m a p s in six
series. T he maps truly are what ha s made the work so widely recognized and
used. Although the text contains discussions that are pioneering contributions
to th e geology of the area, uc h as the effects of bed nd bank materials on
river behavior, they have been overshadowed by the materials with high graph-
ics appeal.
In 1944, Fisk's contribution wa s giant step forward in advancing the state
of knowledge of th e area, nd it remained so for many years. However, s is
almost always the case with such comprehensive work, t soon became dated
as new concepts emerged an d new geological tools were developed. Normally
when this happens, th e newer concepts and data from later individual studies
are periodically synthesized nd new summaries prepared. However, in the
case of Fisk's work, it influenced so m a n y with its impression of detail, accu-
racy, nd precision that it actually deterred later similar efforts (Saucier 1981).
Compounding the situation was the matter of normal problems in the inter-
disciplinary transfer of technical information. Practicing geologists recognized
that th e work wa s becoming outdated, bu t engineers were not (and could not
have been expected to be) cognizant of the newer school of thought. More-
over, Fisk's work, especially his elaborate reconstructions of river channel
patterns and chronology, became widely recognized by and of immense impor-
tance to archaeologists. hey also were not privy to slowly evolving geologi-
ca l concepts nd knowledge, most of which were no t published nd none of
which were summarized in th e literature in their field.
Possibly th e most long-lasting contributions of Fisk in his tenure as consul-
tant to th e M R C were the conversion of geological infonnation into a form
directly useable in engineering practice, nd the awareness he instilled in engi-
neers of the value of a sound understanding of the ffect of geologic processes
in alluvial settings. Fisk's 1944 study epitomizes the former, and therein lies
another problem. Fisk recognized that engineers could no t us e information
that wa s presented n the context of multiple hypotheses, dissenting profes-
sional opinion, or that wa s heavily caveated with degrees of uncertainly.
Therefore, he presented his results largely without qualification or alternate
interpretations. Unfortunately, this sometimes involved omitting mention of
features nd topics for which he ha d no explanation. Eventually, significant
Chapte r Introduction
problems in th e us e of hi s works developed mong scientists in several
disciplines.
Realization even by geologists of the extent and consequences of th e limita-
tions of Fisk's 1944 study ha s been slow in developing, especially as related to
th e chronology and history of river changes, terrace stratigraphy, and modes of
valley formation. fe w alternate interpretations were offered rather quickly
(e.g., Doering 1956 , Durham 1962 , Leighton and Willman 1950), bu t hard
evidence was much slower in materializing. Specific deficiencies in existing
concepts became apparent, and a new chronological framework fo r terraces,
valley trains (glacial outwash deposits), nd meander belts eventually devel-
oped as a direct spinoff from th e detailed mapping of environments of deposi-
tion at WE S (Saucier 1968, 1978, 1987; Saucier and Fleetwood 1970). he
first relatively complete (but not detailed) statement of new concepts and a
suggested revised chronology of valley events appeared in Autin et al . (1991).
T he most significant limitations of th e 1944 work of Fisk are directly attrib-
utable simply to major advances in general geologic knowledge and theory that
have developed within th e past 50 years. Fisk assumed that glacioeustacy was
th e fundamental control on fluvial form nd process, and he logically based hi s
chronological concept on th e best model available from the midwestern United
States fo r glacial and interglacial cycles. However, that model ha s changed
dramatically over th e years. or example, Fisk based his chronology on th e
then-widely-accepted simple Pleistocene glacial sequence consisting of five
glacial and four interglacial stages, whereas the more widely accepted present
models are much more complex with possibly as m a n y as eight cycles (Beard,
Sangree, and Smith 1982; Richmond and Fullerton 1986) of varying duration
and intensity. T he new models are based heavily on oxygen isotope data from
deep sea cores~a technology that did not exist in th e 1940s.
If Fisk actually erred in judgment, it wa s with regard to his attempt to
assign precise age estimates to all Mississippi Valley events, ncluding esti-
mates to within 10 0 years fo r all Mississippi River abandoned courses and
cutoffs. hese estimates have proven to be wrong in both relative and abso-
lute terms, to have been based on wrong assumptions, nd to be essentially
beyond th e state of th e art even today. ve n with radiocarbon dating and th e
extensive data from th e archeological record, it m ay never be possible to do
what Fisk attempted in 1944. As will be discussed later, there are still ambi-
guities in the fundamental relationships between whole abandoned meander
belts that will require extensive field investigations to resolve before more
detailed reconstructions are possible.
Even after extensive consideration, there ar e aspects of th e mechanics of
meander belt initiation, growth, nd decay that are still unresolved. Meander
belt life cycles apparently vary temporally and spatially, bu t th e precise causal
factors are not known. Hence, anything other than rough age approximations
are meaningless and misleading.
Other aspects of Fisk's 1944 study that require revision include his over-
estimation of th e effects of base level changes on th e formation of the alluvial
valley, hi s excessive emphasis on faulting and fracturing, his rejection of th e
eolian origin of loess, and his failure to recognize the effects of climate change
on both landforms and geomorphic processes. Once again, Fisk only reflected
th e accepted hypotheses of his time, m a n y of which have subsequently been
rejected or significantly modified as geologic knowledge ha s increased.
Consideration of th e large number of studies that have been accomplished
since th e works of Fisk will show that th e state of the art of Lower Mississippi
Valley geomorphology and geology not well balanced, either topically or
geographically. Despite th e limitations previously mentioned, th e area m u s t
rank as on e of th e best known large alluvial valleys in th e world rom th e
viewpoint of engineering geology. Subsurface conditions have been exten-
sively and intensively explored primarily as a consequence of th e history of
major flood control, navigation, nd water resources management projects by
th e U . S . Army Corps of Engineers. Consequently, much is known about geo-
morphic processes and the geotechnical properties of the deposits. Ironically,
however, th e alluvial valley is relatively poorly known from purely geologic
perspective, especially with regard to stratigraphy. Few studies of sedimentary
mechanics nd facies elationships have ever been undertaken.
Comparatively, th e deltaic plain ha s been much more extensively explored
than th e alluvial valley per se and s much better known in a geological sense.
T h a t knowledge is a direct consequence of several decades of intense investi-
gations by petroleum nd geophysical companies aimed at both better under-
standing th e Mississippi delta itself as well as the fundamental aspects of th e
occurrence and recovery of oi l an d ga s in large deltaic systems. A very large
percentage of th e numerous stratigraphic, petrologic, structural, paleontologic,
and chronologic studies that have been undertaken by universities and state
agencies have been funded directly or indirectly by the petroleum industry.
More recently, investigations of coastal and wetland processes relevant to
deltaic ecology and land loss processes have contributed valuable new geologic
data and concepts.
Intent and Scope of the Present Study
This volume is ntended s th e first comprehensive overview and synthesis
of th e geomorphology and geology of the Lower Mississippi Valley-both th e
alluvial valley and the deltaic plain-since 1944. However, it will vary from
that earlier classic work in several respects.
A primary difference is an attempt in th e present synthesis to present geo-
logical information and concepts to an audience of no t only engineers and
geologists bu t also scientists in a broad ange of disciplines. It is primarily a
document funded by and intended fo r the U.S. Anny Corps of Engineers, bu t
not just fo r the geotechnical, foundation design, potamology, nd similar
Chapte r Introduction
engineering functions of that organization. he synthesis also takes into con-
sideration th e informational needs of those concerned with such activities as
basin planning, environmental assessments and mitigation, and cultural and
natural resources management.
Engineering geology in its broadest context is th e appropriate category fo r
classifying this volume; however, it is not a "how-to" manual consisting of
unequivocal answers. either is it primarily a theoretical treatise focusing on
evaluating th e strengths and weaknesses of alternative hypotheses and para-
digms. he synthesis hopes to achieve a balance between th e tw o extremes by
presenting th e generally accepted concepts and also by providing a discussion
of th e degree of confidence in th e interpretations. t strives to separate pure
speculation and hypothesizing (which unfortunately is all that exists in some
cases) from that which is well founded nd scientifically tested. t does not
dwell on or attempt to resolve controversial issues.
Because of this approach, nd in comparison to th e emphatic and unequivo-
ca l nature of Fisk's 1944 study, some aspects of this volume m ay appear to be
a major step backward rather than an advancement of knowledge. hi s is
especially true with regard to th e chronological reconstructions. However, s
ha s been pointed out, th e earlier study attempted to present estimates that
are now regarded as being unjustified in detail and precision. he present
volume presents much less detail, bu t detail fo r which there is recognized
evidence.
T he organization and ection content of this volume involves some difficult
tradeoffs between logical order of discussion and data presentation and the
interests and backgrounds of the user audience. For example, th e decision to
separate discussions of mode of origin, lithology, nd geotechnical characteris-
tics of depositional environments into separate parts-not necessarily logical to
some-was done to accommodate th e different interests and needs of geologists
versus engineers. With a broadly multidisciplinary audience in mind, this
writer intentionally adopted a writing style comparable to that contained in
publications like American Scientist or Scientific American.
Geographically, this volume is estricted to the Lower Mississippi Valley
below the approximate latitude of Cape Girardeau, Missouri, and to the lower
reaches of its principal tributaries (Figure 1). Discussion and mapping is
limited to th e area downstream from Little Rock, Arkansas, on th e Arkansas
River, below Alexandria, Louisiana, on the R ed River, nd south of th e
Arkansas-Louisiana border on th e Ouachita River. Considerable information
on th e Quaternary geology exists for th e more upstream portions of those
rivers, and interested readers are referred to th e works by L.M. Smith (1986),
Smith and Russ (1974), nd Fleetwood (1969). Quaternary deposits and for-
mations above th e mouths of smaller tributaries re no t mapped and discussed,
bu t readers are referred to Saucier (1987) as an example of some of the infor-
mation that is available. he entire Mississippi River deltaic plain and a por-
tion of th e chenier plain in southwestern Louisiana ar e included in the scope of
this volume. Gould and McFarlan (1959) is the primary reference fo r
Chapte r Introduction
GULF OF MEXICO
30 0 KM
Figure . T he Mississippi alluvial valley, deltaic plain, and chenier plain, and the total distri-
bution of Quaternary deposi ts n the Lower Mississippi Val ley portion of th e Gulf
Coastal Plain
information on th e remainder (western portion) of the chenier plain. he dis-
cussion and mapping of th e deltaic plain are limited to th e subaerial portion of
that feature: Coleman (1988) nd Coleman and Roberts (1988) contain a sum-
m a r y of th e geology of th e offshore areas and subaqueous delta platform.
Quaternary deposits (fluvial terraces and related formations) of th e uplands
adjacent to th e alluvial valley are discussed in this volume; however, detailed
mapping is generally limited to narrow band flanking th e Holocene alluvial
plain.
T o avoid excessive length, readers are frequently referred to original
sources for specific detail nd documentation. or example, when radiocarbon
dates are discussed, complete citations with error limits, laboratory numbers,
precise locations, and similar data are intentionally not presented, even in
tabular form. t is believed that readers must be cognizant of all aspects of th e
dates, especially their specific contexts, to allow us e in future research or
interpretations.
Methods and Limitations
There are known extensive data gaps in the knowledge of the geomor-
phology and geology of th e Lower Mississippi Valley, bu t it was beyond th e
scope of this effort to undertake any field investigations or to develop any new
information. S o m e limited ne w interpretations are offered, bu t these relate to
resolving inconsistencies in existing data sets and th e problems normally
encountered when data from multiple sources and dates are synthesized into a
single, and sometimes ne w format.
It is acknowledged that because this writer initiated and conducted m a n y of
th e investigations on which this report is based and developed, it is heavily
flavored by hi s experiences and professional opinion. Hopefully, however, it
is not adversely biased or lacks objectivity. Where th e writer's opinion does
not reflect exposure to peer review or general acceptance, and where data from
hi s unpublished files are used, it is so acknowledged.
Subsurface nvestigations
Borings. or well over 10 0 years, it ha s been recognized that th e Missis-
sippi alluvial valley and deltaic plain are underlain by thick sequences of allu-
vial deposits. acking outcrops or bank exposures more than a few tens of
feet high, even before th e turn of th e century, scientists logically took keen
interest in samples from borings for clues to deltaic plain formation, and engi-
neers searched for answers as to the thickness and nature of th e deposits that
providing poor foundation and 1874,
1884; Wilson 1881).
Chapte r Introduction
Although the M R C took a pioneering role in th e engineering applications of
subsurface investigations, until th e 1930s m o s t data were generated as result
of water wells drilled fo r irrigation in th e alluvial valley area, and borings nd
wells drilled as part of petroleum exploration an d development in th e deltaic
plain area. More than five decades ago, Russell (1940) observed that th e Mis-
sissippi lluvial valley must be th e best explored thick alluvial sequence in th e
world. ince that time, th e amount of subsurface data available ha s increased
by orders of magnitude.
B y far th e largest collection of subsurface data on th e area exists in the files
of W E S . As part of th e more than 30-year effort to ystematically m ap th e
depositional environments of the Mississippi Valley, it ha s been standard prac-
tice to collect as much subsurface data as re practicably available. Routinely
surveyed sources include U . S . Army Engineer District offices, state highway
departments, th e U . S . Geological Survey groundwater division offices, the
U . S . Soil Conservation Service, private well drilling firms, petroleum com-
panies, consulting foundation engineering finns, and published eports. s
consequence of th e W E S mapping efforts for the Corps, the W E S files contain
data on an estimated 250,000 borings.
In amass ing these data, eldom ha s it been possible to examine actual cores
or samples. his generally ha s been possible only in terms of special projects,
such as Corps locks and dams, where detailed geologic investigations have
been involved. Rather, th e typical data used in the regional mapping effort
have consisted of descriptive driller's logs or laboratory logs and some geo-
technical test results.
Interpretations of subsurface
s > >
Approved or public eleases-
The contents of this report are not to be used for advertising,
publication, or promotional purposes. Citation of trade names
does not constitute an official endorsement or approval of th e us e
of such commercial products.
Prepared by Roger T. Saucier
U.S. Army Corps of Engineers
Waterways Exper iment Station
3909 Halls Ferry Road
Prepared fo r T he President
Mississippi iver Commission
Vicksburg, MS 39181-0080
Definitions
Holocene meander belts and distributaries
Deltaic and Chenier Plain Segments 9
Uplands, distributary ridges, nd cheniers 9
Interdistributary lowlands and basins
Continental Glaciations 6
Glacial response model
Effects of sea level change 6
Reconstructing sea level history
Tectonics and Diapirism
-Landfonns and Geomorphic Processes 9
Erosional Landscapes
Stream entrenchment
Upland graveliferous deposits
Lacustrine Environments 2 9
Prodelta deposits
Pimple mounds 6 2
Pleistocene Terrace Complexes
Interdistributary 04
"Eowisconsin" Stage Events nd Deposits 3
Background 2 2 3
Late Wisconsin Stage Valley Entrenchment
Mississippi River Meander Belts
Stage 2 6 6
White/Black River Lowland
R ed River Meander Belts
Lafourche 2 82
L a n d doming an d inking 9 5
Landsliding and bank caving 9 6
Faults nd lineaments 9 8
Faulting and Regional Fracturing 01
Mississippi Valley area
Groundwater Occurrence 06
Mass Movements 09
Landsliding 12
References 3 4
Appendix B : Index
plain, nd th e total distribution of Quaternary deposits in
th e Lower Mississippi Valley portion of th e Gulf Coasta l
Plain
from Weinstein et al . 1979) 17
Figure 3 . Standard geologic column applicable to the Lower
Mississippi Valley area 3 3
Figure 4. Geologic column fo r the Quaternary period showing
conceptual stages nd a generalized sea level curve
indicating eustatic cycles (modified from Beard, Sangree,
and Smith 1982)
40
Figure 5 . History of post-Illinoian sea level variations in the Gulf
C o a s t area (dashed lines indicate interpretations by the
author) (adapted from Revelle 1983, Goodwin et al . 1991,
and other sources)
Figure 6. Major structural features of the Lower Mississippi Valley
(modified from Autin et al . 1991)
Figure 7. Comparative interpretations of th e configuration of the
entrenched uballuvial surface in a portion (Mossy L a k e
quadrangle) of the Yazoo Basin of west-central Mississippi
(from Kolb et al . 1968, and subsequent revised editions) .. 75
Figure 8. Alluvial fans. A: Small, discrete, symmetrical fa n of
unnamed creek near Leverett in Tallahatchie Co., M S
(Plate 8); B : Coalesced, smal l fans forming alluvial
apron (in cultivation) west of U . S . Highway 61 near
Yokena in Warren Co., M S Plate 9 )
Figure 9 . Configurations of and channel patterns on three alluvial
fans representing a range of types and sizes: A=Teoc
and (B ) Late Wisconsin valley train in D ee quadrangle,
Poinsett Co., AR (adapted from Whitworth 1988,
Saucier 1964)
9 5
Figure 11. Relict braided channel patterns on valley trains. A: Early
Wisconsin-age channels near Weiner in Poinsett Co., AR
(Plate 6) marked by entrenched local drainage; B : a te
Wisconsin-age elict channel east of Crowley's Ridge near
Harrisonburg in Poinsett Co., AR (Plate ) marked only by
darker soil tones (between arrows) 9 6
Figure 12 . A ypical meander belt ridge (A) within th e context of th e
Mississippi lluvial valley (modified from Fisk 1947) and
an illustration (B ) of the principal depositional environ-
ments involved modified from Allen 1964) 10 0
Figure 13 . Primary and econdary depositional environments and
related channel features of a typical meander belt (from
Gagliano nd va n Beek 1970)
Figure 14. Natural levees. A: Natural levee, clearly evident by
distribution of cultivated fields and hardwood forest
vegetation (between arrows), along the Mississippi River
near Gramercy in St. James Ph., L A (Plate 12); B : Crevasse
channels (marked by arrows) on natural levee flanking L a k e
Providence, n abandoned channel in E a s t Carroll Ph., L A
(Plate 9 )
Figure 15 . Crevasse splays. A: Anastomosing channels from large,
natural crevasse that formed along th e south side of False
River in Pointe Coupee, Ph., L A (Plate 11) when it was the
active course of the river; B : Crevasse splay esulting
from failure of an artificial levee (Morganza Crevasse of
April 1890) near Morganza in Pointe Coupee Ph., L A 10 4
VIM
Figure 16 . Distributaries. : bandoned channel and natural levees
(cultivated reas) of th e D e e r Creek distributary near Valley
Park in Issaquena Co., MS Plate 9); B : ain channel and
branches of th e River distributary near
Walters in Catahoula Ph., L A (Plate 10) 10 6
Figure 17 . T wo large distributary systems originating from crevasses
along Arkansas River meander belts northeast of Monroe
in northeastern Louisiana (from Kidder and Saucier 1991)
(meander belt details and traces of older meander belts
omitted to avoid confusion) 108
Figure 18. Point bar environment. A: Sand waves being deposited on
an actively accreting point bar along the Chute of Island
N o. 5 bend of th e Mississippi River in Tipton Co., T N
(Plate 6); B : oint ba r ridges and swales of on e meander
sequence truncating another east of th e Tensas River near
Ferriday in Concordia Ph., L A Plate
Figure 19 . Point ba r environment. A: Complex accretion topography
indicating movements of several different Mississippi River
bends west of St. Francisville in West Feliciana Ph., L A
(Plate 11); B : oint bar ridges and swales veneered with
natural levee deposits near th e present river channel at
Duncan Point south of Baton Rouge in E a s t Baton Rouge
Ph., L A (Plate 11)
HI
Figure 2 0. haracteristic stages in th e life cycle of a typical neck
cutoff along a major stream in th e Mississippi lluvial
vaUey 114
Figure 2 1. Abandoned channels. A: Cocodrie L a k e north of Monterey
in Concordia Ph., L A (Plate 10), a classic-shaped Missis-
sippi River cutoff with oxbow lake and filling of arms
below point of cutoff; B : Smal l batture channel connect-
in g oxbow lake near Raccourci O ld River in Pointe Coupee
Ph., L A (Plate 11) with Mississippi River (channel filling
located between arrows deposited between 1848, date of
cutoff, and 1959, date of photo) 115
Figure 2 2 . Abandoned channels. : ypical batture channel pattern
as exemplified by T he Chenal in th e lower arm of th e False
River cutoff in Pointe Coupee Ph., L A Plate 11) (aban-
doned channel limits indicated by arrows); B : Essentially
filled abandoned channel characterized by s w a m p forest
vegetation west of Centennial Island in Crittenden Co.,
AR (Plate 6)
detectable by characteristic vegetation assemblage
and soils (between arrows) along the Tensas River
northeast of Sicily Island in Tensas Ph., L A
(Plate 10); B : Abandoned channel southwest of Hughes
IX
in L ee Co., AR (Plate 7) sufficiently filled and
well drained to allow agriculture limits located
between arrows detectable by absence of point bar
ridges nd wales, vegetation, nd darker soil tones) 118
Figure 2 4. Abandoned courses. A: Mississippi River abandoned
course now occupied by th e Tensas River southeast of
Sicily Island n Tensas Ph., L A (Plate 10), estimated
channel bank lines indicated by arrows);
B : Underfit streams Hopson and Cassidy bayous) that
have exceeded and largely obliterated th e limits of
th e former Mississippi River course northeast of
Tutwiler in Quitman and Tallahatchie Cos., MS Plate 7) 12 0
Figure 2 5 . Configurations of Mississippi River meander belts as
defined by the extent of the point ba r environment (A),
and distribution of neck and chute cutoffs (B ) 12 2
Figure 2 6 . Backswamp. A: Nearly featureless, forested backswamp
tract in the Atchafalaya Basin south of Lottie in
Pointe Coupee Ph., L A Plate 11); B : R im swamp in the
Spanish Lake rea south of Baton Rouge at th e junction
of Ascension, E a s t Baton Rouge, nd Iberville parishes,
L A Plate 11) (cultivated areas lie on the Prairie
Complex, nd th e Mississippi River meander belt lies to
th e west beyond the limits of the photo) 12 8
Figure 2 7. Sand dunes. A: Well-defined tract of sand dunes
(between arrows) between braided channels south of
Naylor in Ripley Co., M O Plate 5) some large depres-
sions between dunes still orested); B : More intensely
cultivated nd subdued bu t still visible dunes (lighter
soil tones) nd depressions darker soil tones) north-
west of Walnut Ridge n Lawrence Co., AR Plate 5) 13 5
Figure 2 8. Idealized urface nd ubsurface distribution of environ-
ments of deposition t several stages in a typical delta
cycle (from Frazier and Osanik 1965)
Figure 2 9 . Block diagram showing relationships of subaerial nd
subaqueous deltaic environmenls of deposition in a
single delta lobe from Coleman and Roberts 1991) 13 9
Figure 3 0. Hypothetical edimentary sequence resulting from everal
overlapping deltaic cycles showing major environments of
deposition (from Coleman and Gagliano 964) 140
Figure 3 1. Highly popular, bu t outdated, nterpretation of
Holocene delta complexes A) , nd currently
accepted nterpretation (B )
Figure 3 2 . Distributaries. A: Bayou Lafourche, a major Mississippi
River distributary in Terrebonne Ph., L A (Plate 14) marked
by well developed natural levees cleared fo r agriculture;
B : mall distributaries in southern Terrebonne Ph., L A
(arrows) indicated by conspicuous relict channels but
whose subsided natural levees are barely discernible by
slight vegetation differences (shrubs) from adjacent marsh 14 2
Figure 3 3 . Inland swamp. : early featureless inland swamp south-
west of L a k e Maurepas in Ascension Ph., L A (Plate 12 )
(linear features are abandoned railroad spurs used in
cypress logging operations in th e early 20th century);
B : nland s w a m p in a more-coastal setting, interrupted
by areas of freshwater marsh (lighter tones), near
Calumet in St. Mary Parish, L A (Plate 13 ) 144
Figure 3 4. Intratidal marsh. : rackish marsh east of L a k e Borgne
in St. Bernard Ph., L A (Plate 14) characterized predominantly
by three-cornered grass (Scirpus olneyi); B: Well-drained
salt marsh along Mississippi Sound in St. Bernard Ph., L A
(Plate 12 ) composed mainly of black rush (Juncus
roemerianus) and wiregrass (Spartina patens) 146
Figure 3 5. Intratidal marsh. A: Freshwater marsh, dominated by
cattail (Typha spp.) and roseau cane {Phragmites
communis), created after 1891 a crevasse splay in
Garden Island B ay in Plaquemines Ph., L A (Plate 14);
B : Nearly uninterrupted tract of floating fresh marsh
west of L a k e Salvador in Lafourche Ph., L A (Plate 14)
(tonal patterns on marsh caused by episodes of deliberate
burning to enhance marsh productivity)
14 8
Figure 3 6 . Model showing the distribution of environments at several
transgressive stages in a deteriorating delta lobe (from
Penland and Boyd 1981) 15 2
Figure 3 7. Beaches and barriers. : rosional headland in th e Isles
Derniers area of southern Terrebonne Ph., L A Plate 14)
(intratidal marshes represent surviving portions of th e
delta complex); Portion of a flanking
barrier island of the Isles Derniers chain 15 4
Figure 3 8. Reefs. xtensive oyster reefs extending southward
into th e Gulf of Mexico from Marsh Island in Iberia
Ph., L A (Plate 13 )
Figure 3 9 . Cheniers. runcated series of relict beaches, indicating
former Gulf shorelines, fomring Pecan Island, a large
chenier in Vermilion Ph., L A (Plate 13 ) 15 8
Figure 40. Model of chenier development showing surface physiog-
raphy and subsurface sedimentary facies (from Gould
and McFarlan 1959) 16 0
XI
mounds on silty clay soils (Early Wisconsin valley
train deposits) east of Bald Knob in White Co., AR
(Plate 6 ); B: imple mounds of moderate size and
density on sandy loam soils (Early Wisconsin valley
train deposits) southwest of Naylor in Ripley Co.,
M O (Plate 5) 16 3
Figure 42 . Sand blows and fissures. : Dense scatter of relatively
undisturbed sand blows on Late Wisconsin valley train
deposits near Rivervale in Poinsett Co., AR (Plate 6);
B : Sand blows and fissures well diffused by cultivation
on Late Wisconsin valley train deposits southeast of
Lepanto in Poinsett Co., AR (Plate 6 )
near-surface portions of the Prairie Complex 17 4
Figure 44. Model showing the distribution of subenvironments nd
deposits of a typical valley train during early (A )
and late (B ) phases of outwash deposition during
waning glaciation (from Whitworth 1988) 184
Figure Longitudinal slope, width, thickness, nd general
composition (soil type frequency diagram) of natural
levee deposits from near Donaldsonville (Plate 11) to
near Fort Jackson, L A (Plate 14) from Kolb 1962) 19 0
Figure 46 . Diagrammatic cross section of a meander belt showing
typical distribution of deposits and sedimentary struc-
tures in a point ba r sequence (from Gagliano and
va n Beek 1970) 19 2
Figure 47. Locations and early interpretations of the ages of fluvial
and marine features of th e Prairie Complex in southwestern
and outheastern Louisiana (from Saucier 1977b) 4
Figure 48 . Configuration of th e entrenched surface (first horizon) on
Wisconsin-age deposits of the Prairie Complex as mapped
on th e N ew Orleans E a s t and Spanish Fort 1:24,000-scale
quadrangles 2 3 8
Figure 49A. onfiguration of th e to p of the western half of the
Holocene-age Pine Island Beach Trend buried beneath
deltaic deposits in th e greater N ew Orleans area 1
Figure 4 9 B . onfiguration of the top of the eastern half of the
Holocene-age Pine Island Beach Trend buried beneath
deltaic deposits in th e greater N ew Orleans area 2
Figure 50. stimates of ages of channel tages (meander belts) of
major rivers, delta complexes, nd cheniers; modified
from Autin et al . 1991) 5
XI I
Figure 5 1. Evolution of a part of th e Yazoo Meander Belt (Stage 2 )
as reconstructed using geomorphological and archeological
evidence from th Teoc Creek and Neill Sites (modified
from Connaway, McGahey, nd Webb 1977) 5
Figure 5 2 . Major structural features of the N ew Madrid Seismic Zone
along with epicenters of microearthquakes (modified from
Luzietti et al . 1992)
Figure 53 . Distribution of liquefaction features (sand blows and
fissures) in th e N ew Madrid Seismic Zone (density classi-
fication based on estimated percentage of ground surface
covered by extruded sand prior to widespread disturbance
by agriculture) 9 2
Figure 5 4. Typical characteristics of liquefaction features in th e
N ew Madrid Seismic Zone as revealed along banks of
drainage ditches (modified from Wesnousky &
Leffler 1992) 2 9 3
Figure 5 5 . Known and inferred faults and major lineaments in the
N ew Madrid Seismic Zone (compiled from Crone 1992 ;
Heyl and McKeown 1988; Schweig, Marple, and L i 1992 ;
Zoback et al . 1980)
3 00
Figure 5 6 . Typical bank failure mechanisms in various alluvial and
deltaic environments of deposition (from Tumbull,
Krinitzsky, and Weaver 1966) 3 10
Figure Al. Geotechnical characteristics of shallow Pleistocene
deposits from beneath th e deltaic plain A3
Figure A2 . Geotechnical characteristics of Wisconsin-Stage braided
stream valley train) interfluve deposits
deposits of th e alluvial valley
deposits of th e alluvial valley
distributary deposits of the deltaic plain
distributary deposits of the deltaic plain
of the deltaic plain ll
XIII
Figure A10. eotechnical characteristics of Holocene s w a m p deposits
(backswamp and s w a m p environments)
of the deltaic plain 12
Figure All. eotechnical characteristics of Holocene prodelta deposits
of the deltaic plain 13
Figure A12. eotechnical characteristics of Holocene intradelta
deposits of th e deltaic plain 14
Figure A 1 3 . omparison of water content test data from various
and Holocene fluvial and
Figure A14. omparison of liquid limit test data from various
Pleistocene and Holocene fluvial and deltaic
environments 16
Figure A15. omparison of plastic limit test data from various
Pleistocene and Holocene fluvial and deltaic
environments 17
Figure A16. omparison of plasticity index test data from various
Pleistocene and Holocene luvial nd deltaic
environments 18
Figure A17. omparison of dry density test data from various
Pleistocene and Holocene fluvial and deltaic
environments 19
Figure A18. omparison of wet density test data from various
Pleistocene and Holocene fluvial and deltaic
environments 0
Figure A19. omparison of cohesive strength test data from various
Pleistocene and Holocene fluvial and deltaic
environments 2 1
Figure A20. omparison of blow count test data from various
Pleistocene and Holocene fluvial an d deltaic
environments 2
Figure A21. omparison of D 10 grain ize test data from various
Pleistocene and Holocene fluvial environments 2 3
List of Tables
Glacial/Interglacial Cycle in the Lower Mississippi
Valley (from Autin et al. 991) 3 8
Table 2 . Generalized, Composite Stratigraphic Column fo r th e
Lower Mississippi Valley 5 6
X IV
of Various Geologic Units in Louisiana (from
Autin et al. 1991) 171
Table 4. Occurrence of Minor Sedimentary Structures in Holocene
Fluvial Depositional Environments
Deltaic Depositional Environments
Marine Depositional Environments
Preface
In M ay 1941, th e U . S . Army Corps of Engineers, Mississippi River C o m -
mission ( M R C ) , Vicksburg, Mississippi, hired D r. Harold N . Fisk of Louisiana
State University, Baton Rouge, Louisiana, s a geological consultant nd
him to prepare comprehensive summary of th e geology of th e Lower
Mississippi Valley. T he resultant product, Geological Investigation of the
Alluvial Valley of the Lower Mississippi River, was published by th e M R C in
December 1944 nd oo n became the authoritative reference in th e field nd
eventually a classic.
Although m a n y of th e concepts and interpretations set forth in 1944 have
stood th e test of time, others have no t as ne w tools and techniques have
emerged, new hypotheses have been offered and tested, and geological
knowledge in general ha s advanced dramatically. o eflect th e advances of
th e past 50 years, which include a voluminous but dispersed literature, huge
amounts of new and sometimes unpublished data, nd evolving concepts of
valley history and chronology, th e M R C agreed in October 1992 to sponsor th e
preparation of a new, comprehensive geological and geomorphological
synthesis.
T he synthesis was prepared between October 1992 and December 1994 by
D r. Roger T . Saucier while assigned part time as a Physical Scientist to th e
Earthquake Engineering and Geosciences Division ( E E G D ) , Geotechnical
Laboratory (GL), U . S . Army Engineer Waterways Experiment Station (WES),
Vicksburg, Mississippi. General administration of th e project wa s provided by
Messrs. Frank Weaver, Lawrence Cave, nd Tony Y o u n g of the Geotechnical
and Materials Division, U . S . Army Engineer Division, Lower Mississippi Val-
ley L M V D ) , Vicksburg, Mississippi. Funds were provided by th e U . S . Army
Engineer Districts, Vicksburg, N ew Orleans, nd Memphis, t th e direction of
th e M R C .
D r. Saucier wa s uniquely qualified to prepare th e synthesis s a conse-
quence of his more than 3 5 years of detailed mapping and investigation of
multiple aspects of th e engineering geology of the Lower Mississippi Valley
while employed t W E S nd ls o serving as a private consultant. He ha s
authored th e only tw o limited ttempts of the last 50 years to summarize
aspects of th e geology of th e area, nd his research focus, reflected n dozens
of publications, ha s been on interdisciplinary considerations and pplications
X V I
ranging from rcheology to paleoseismology. D r. Saucier assembled and
reviewed th e literature for this synthesis, developed the outline and wrote th e
text, nd prepared most of the figures and plates.
Technical guidance, consultation, critical review, and ssistance in many
aspects of th e project were provided by D r. Lawson Smith of the E E G D ,
W E S , who also envisioned the need for the synthesis and served as a pro-
ponent of the project. Substantial assistance wa s provided by others in prepar-
in g tw o parts of th e synthesis. Messrs. T im Ethridge ( L M V D ) , Mike Bishop
(WES contractor), and William Murphy ( E E G D ) assembled and digitized the
data and implemented the computer contouring of the suballuvial surface and
prepared the graphical output. Mr. Ken Stroud, graduate student at th e Univer-
sity of Southern Mississippi, conducted under contract to W E S th e assembly,
evaluation, tatistical analysis, nd portrayal of th e data on th e geotechnical
characteristics (Appendix A). Drafting and scientific illustration associated
with th e numerous figures and plates were accomplished by and under the
direction of Messrs. William Park and Alan Middleton of the W E S Visual
Production Center, Information Technology Laboratory.
Peer review of th e manuscript wa s provided by D r. Whitney Autin of the
Institute for Environmental Studies, Louisiana State University, and D r. L a w -
son Smith and Mr. Joseph Dunbar, E E G D , W E S .
T he project was accomplished under the general supervision of Mr. Jo e L .
Gate, Chief, Engineering Geology Branch, E E G D , D r. A.G. Franklin, Chief,
E E G D , and D r. W.F. Marcuson III, Director, GL , W E S .
At th e time of publication of this report, Director of W E S wa s D r. Robert
W . Whalin. C o m m a n d e r wa s C O L Bruce K. Howard, E N .
Th e contents of this report ar e no t to be used for advertising, publication,
or promotional purposes. itation of trade names does no t constitute an
official endorsement or approval of the use of such commercial products.
XVII
Conversion Factors, Non-SI to
SI Units of Measurement
N o n - S l units of measurement used n this report ca n be converted to SI units
as follows:
gallons (U.S. iquid)
1 Introduction
Previous Investigations
With th e possible sole exception of th e insightful work of Lyell (1847), th e
earliest geological studies in the Lower Mississippi Valley area that reflect
reasonably modem concepts generally date between th e 1860s and th e early
1900s. hey include such notable works as those by Harris (1894) in Arkan-
sas; Hilgard (1860) in Mississippi; and Stubbs (1892), and
Veatch (1906) in Louisiana; Safford (1869) in Tennessee; nd Swallow (1877)
in Missouri. Emphasis in these publications was on agriculture and mineral
resources, but they also included descriptions of outcrops, springs, nd special
features nd devoted considerable attention to groundwater. Without question,
th e focus was on th e pre-Quaternary uplands. his reflects trend that was to
diminish but not disappear for m a n y decades, i.e., geologists were interested in
th e uplands and "hard rock" and not alluvium. he only significant exceptions
were studies by Marbut (1902) of the lowlands of southeastern Missouri nd
by Stephenson and Crider (1916) of a portion of northeastern Arkansas.
Fundamental aspects of th e geology of the alluvial valley, such as th e pres-
ence of glacial outwash (valley trains), multiple Mississippi River meander
belts, nd effects of sea level variations, were well known by th e beginning of
th e 20th century. However, they were not comprehensively or systematically
described by geologists during these early years. Soil scientists were actually
th e first to devote serious attention to the alluvial plain, and by the 1920s,
there were published soil surveys fo r a number of counties in Arkansas, Loui-
siana, Mississippi, and Missouri. These constitute th e first rather large-scale
maps of Quaternary physiography and surficial deposits.
A major turning point in th e documentation of Mississippi Valley
Quaternary geology occurred in th e early 1930s when th e Louisiana Geological
Survey initiated a series of truly comprehensive, large-scale, geological bulle-
tins covering parishes in the southern part of that state (e.g., Howe and Moresi
1931, 1933) . This series wa s later extended into central Louisiana (Chawner
1 9 3 6 ) and also marks th e first involvement of Fisk (1938) in Lower Missis-
sippi Valley geology. T he series focused on mineral resources (oil, gas, salt,
and sulphur), nd the first parish selected (Iberia) wa s because of its economi-
cally important salt domes. Nevertheless, th e bulletins provided n
Chapte r Introduction
unprecedented wealth of information on th e Quaternary of th e Mississippi
Valley. During th e decade of the 1930s, other states such as Mississippi nd
Tennessee initiated similar series bu t did not include counties in th e alluvial
valley area.
Prior to th e 1930s , geological studies in th e Lower Mississippi Valley area
were largely descriptive, concentrating on outcrops, physiographic features, and
stratigraphic correlations. In terms of alluvial and deltaic deposits, little atten-
tion ha been devoted to relating them to geomorphic processes and explaining
their origin and variability. Relatively fe w borings ha d been drilled; hence th e
nature of th e subsurface beneath the alluvial plain wa s largely unknown. Con-
sequently, geological knowledge wa s of limited utility to engineers who were
concerned with siting dams, designing levees, employing river regulation, nd
similar activities.
Another major turning point occurred n the early 1940s when the Missis-
sippi River Commiss ion ( M R C ) retained Harold N . Fisk, a geologist at Louisi-
ana State University ( L S U ) , s a consultant. Between 1941 nd 1948, Fisk
and a team of graduate students prepared 3 0 special geological reports fo r th e
M R C on such topics as bank erosion, levee underseepage, faulting, and lluvial
deposits and landforms, nd geologic studies of proposed lock and da m ites
and other structures n Louisiana, Arkansas, Mississippi, and Texas . Most of
these eports were never published; however, during th e eight-year period, Fisk
did publish tw o monographs (Fisk 1944, 1947) of valley-wide scope that were
to soon become widely known and used, nd eventually to achieve the status
of geological classics. These tw o works marked the beginning of engineering
geology in th e Lower Mississippi Valley.
Fisk's bility to relate the origin, distribution, and characteristics of deposits
to fluvial, deltaic, nd marine processes, nd hence develop a predictive capa-
bility fo r engineers, was largely attributable to tw o significant developments.
First, he wa s able to ake advantage of the first complete coverage of the
Lower Mississippi Valley by large-scale, vertical, erial photography that was
obtained by the U . S . Soil Conservation Service in th e late 1930s. Second, he
wa s able to obtain samples and logs from large number of strategically
placed, carefully drilled, nd logged borings that penetrated the lluvial
sequence. Those borings provided the first truly three-dimensional look t the
deposits of th e alluvial valley and deltaic plain.
During th e decades of the 1950s and 1960s, here wa s a virtual explosion of
th e volume of geological knowledge, ncluding that of direct relevance to
engineering practice. Thousands of site-specific s well as topical studies were
accomplished nd published se e bibliography of Saucier 1966), covering virtu-
ally al l fields of modem geology such as geomorphology, edimentology,
tectonics, eismology, paleontology, stratigraphy, nd chronology. Major
advances in knowledge resulted not only by the greatly increased interest and
efforts by academia an d government bu t also from the dvent of new tools nd
techniques. Paramount among these are geophysics, adiocarbon dating, nd
remote sensing.
U p o n th e departure of Harold Fisk from L S U in 1948 to Humble O il &
Refining Company) , th e focal point for specific engineering geologic investiga-
tions of th e Lower Mississippi Valley, and the continuation of this tradition,
shifted to th e Geology Branch of the U . S . Army Engineer Waterways Experi-
ment ( W E S ) in Vicksburg, Mississippi. Between that date and the present,
hundreds of geological studies of project sites and particular problems have
been conducted. owever, perhaps th e most important contribution wa th e
systematic large-scale (1:62,500) mapping of geomorphic surfaces and subsur-
face soils conditions and the inferred environments of deposition fo r essentially
a ll of th e Mississippi alluvial valley and ts major tributaries within the juris-
diction of th e U . S . Army Engineer Division, Lower Mississippi Valley. ight
folios of maps and cross sections, each covering a major basin area, have been
published in limited editions (Fleetwood 1969 ; Kolb et al . 1968; M ay et al .
1984; Saucier 1964, 1967, 1969 ; Smith and Saucier 1971; Smith and R u s s
1974) for us e primarily by th e U . S . Army Corps of Engineers.
Geological studies in th e decade of th e 1970s and continuing to date have
been more precisely focused on particular problem areas and locations and
much more sophisticated in approach. wo trends are evident. irst, there ha s
been a definite reach-out fo r additional tools and knowledge from related disci-
plines such as archeology, botany, chemistry, pedology, climatology, and
oceanography. hi s ha s been necessary not only to resolve problems in chro-
nology and paleoenvironmental reconstructions bu t also to better understand
processes affecting th e development of th e area. Second, it ha s been possible
to go beyond simple knowledge expansion to needed efforts in synthesis and
reanalysis, reinterpretation, and revision.
Because of th e intent of th e present volume, attention is directed toward th e
status of efforts at summarization and synthesis rather than specific investiga-
tions. Since th e first comprehensive look at the entire Lower Mississippi Val-
ley by Fisk (1944), there have been only tw o attempts to give engineers a
single source fo r an overview of th e geology of th e whole area with a discus-
sion of th e latest concepts. A brief summary of th e Quaternary geology of th e
valley wa s prepared in th e mid-1970s (Saucier 1974); however, it was intended
primarily for cultural resources managers. I t contained a new generalized
geologic m ap (approximate scale 1:1,250,000), a discussion of problems with
concepts, and the chronology of Fisk (1944), bu t it did not offer solutions. A
more comprehensive overview of the Quaternary geology of th e valley area,
including a moderately detailed, full color, geologic m ap (scale 1:1,100,000),
was published in 1991 Autin et al . 1991). hi s work, the most definitive
since 1944, provides th e most up-to-date discussions of new concepts of valley
origin and history, including a substantially revised chronology of events. I t is
balanced in scope and approach and intended for a general geology audience.
A primary attribute is its widespread availability~a major benefit in view of
th e limited vailability of the earlier work because of its rather obscure source.
Chapte r Introduction
Assessment of State of the Art
T he latest synthesis of Lower Mississippi Valley geology (Autin et al .
1991) is modest in scope and ha s not been available very long. Therefore, th e
classic 1944 tudy by Fisk is still th e most widely known, if no t widely
accepted, work of its type. espite its age and the fact that m a n y geologists
recognize it ha s significant shortcomings, th e 1944 work retains its appreciable
status several reasons, especially among engineers. several decades it
was the only reference of its type available, it is comprehensive in scope, nd
it wa s for its vintage) magnificent in execution. I t consists of tw o volumes:
a volume primarily of text, and a pocket of 2 6 large, multicolored m a p s in six
series. T he maps truly are what ha s made the work so widely recognized and
used. Although the text contains discussions that are pioneering contributions
to th e geology of the area, uc h as the effects of bed nd bank materials on
river behavior, they have been overshadowed by the materials with high graph-
ics appeal.
In 1944, Fisk's contribution wa s giant step forward in advancing the state
of knowledge of th e area, nd it remained so for many years. However, s is
almost always the case with such comprehensive work, t soon became dated
as new concepts emerged an d new geological tools were developed. Normally
when this happens, th e newer concepts and data from later individual studies
are periodically synthesized nd new summaries prepared. However, in the
case of Fisk's work, it influenced so m a n y with its impression of detail, accu-
racy, nd precision that it actually deterred later similar efforts (Saucier 1981).
Compounding the situation was the matter of normal problems in the inter-
disciplinary transfer of technical information. Practicing geologists recognized
that th e work wa s becoming outdated, bu t engineers were not (and could not
have been expected to be) cognizant of the newer school of thought. More-
over, Fisk's work, especially his elaborate reconstructions of river channel
patterns and chronology, became widely recognized by and of immense impor-
tance to archaeologists. hey also were not privy to slowly evolving geologi-
ca l concepts nd knowledge, most of which were no t published nd none of
which were summarized in th e literature in their field.
Possibly th e most long-lasting contributions of Fisk in his tenure as consul-
tant to th e M R C were the conversion of geological infonnation into a form
directly useable in engineering practice, nd the awareness he instilled in engi-
neers of the value of a sound understanding of the ffect of geologic processes
in alluvial settings. Fisk's 1944 study epitomizes the former, and therein lies
another problem. Fisk recognized that engineers could no t us e information
that wa s presented n the context of multiple hypotheses, dissenting profes-
sional opinion, or that wa s heavily caveated with degrees of uncertainly.
Therefore, he presented his results largely without qualification or alternate
interpretations. Unfortunately, this sometimes involved omitting mention of
features nd topics for which he ha d no explanation. Eventually, significant
Chapte r Introduction
problems in th e us e of hi s works developed mong scientists in several
disciplines.
Realization even by geologists of the extent and consequences of th e limita-
tions of Fisk's 1944 study ha s been slow in developing, especially as related to
th e chronology and history of river changes, terrace stratigraphy, and modes of
valley formation. fe w alternate interpretations were offered rather quickly
(e.g., Doering 1956 , Durham 1962 , Leighton and Willman 1950), bu t hard
evidence was much slower in materializing. Specific deficiencies in existing
concepts became apparent, and a new chronological framework fo r terraces,
valley trains (glacial outwash deposits), nd meander belts eventually devel-
oped as a direct spinoff from th e detailed mapping of environments of deposi-
tion at WE S (Saucier 1968, 1978, 1987; Saucier and Fleetwood 1970). he
first relatively complete (but not detailed) statement of new concepts and a
suggested revised chronology of valley events appeared in Autin et al . (1991).
T he most significant limitations of th e 1944 work of Fisk are directly attrib-
utable simply to major advances in general geologic knowledge and theory that
have developed within th e past 50 years. Fisk assumed that glacioeustacy was
th e fundamental control on fluvial form nd process, and he logically based hi s
chronological concept on th e best model available from the midwestern United
States fo r glacial and interglacial cycles. However, that model ha s changed
dramatically over th e years. or example, Fisk based his chronology on th e
then-widely-accepted simple Pleistocene glacial sequence consisting of five
glacial and four interglacial stages, whereas the more widely accepted present
models are much more complex with possibly as m a n y as eight cycles (Beard,
Sangree, and Smith 1982; Richmond and Fullerton 1986) of varying duration
and intensity. T he new models are based heavily on oxygen isotope data from
deep sea cores~a technology that did not exist in th e 1940s.
If Fisk actually erred in judgment, it wa s with regard to his attempt to
assign precise age estimates to all Mississippi Valley events, ncluding esti-
mates to within 10 0 years fo r all Mississippi River abandoned courses and
cutoffs. hese estimates have proven to be wrong in both relative and abso-
lute terms, to have been based on wrong assumptions, nd to be essentially
beyond th e state of th e art even today. ve n with radiocarbon dating and th e
extensive data from th e archeological record, it m ay never be possible to do
what Fisk attempted in 1944. As will be discussed later, there are still ambi-
guities in the fundamental relationships between whole abandoned meander
belts that will require extensive field investigations to resolve before more
detailed reconstructions are possible.
Even after extensive consideration, there ar e aspects of th e mechanics of
meander belt initiation, growth, nd decay that are still unresolved. Meander
belt life cycles apparently vary temporally and spatially, bu t th e precise causal
factors are not known. Hence, anything other than rough age approximations
are meaningless and misleading.
Other aspects of Fisk's 1944 study that require revision include his over-
estimation of th e effects of base level changes on th e formation of the alluvial
valley, hi s excessive emphasis on faulting and fracturing, his rejection of th e
eolian origin of loess, and his failure to recognize the effects of climate change
on both landforms and geomorphic processes. Once again, Fisk only reflected
th e accepted hypotheses of his time, m a n y of which have subsequently been
rejected or significantly modified as geologic knowledge ha s increased.
Consideration of th e large number of studies that have been accomplished
since th e works of Fisk will show that th e state of the art of Lower Mississippi
Valley geomorphology and geology not well balanced, either topically or
geographically. Despite th e limitations previously mentioned, th e area m u s t
rank as on e of th e best known large alluvial valleys in th e world rom th e
viewpoint of engineering geology. Subsurface conditions have been exten-
sively and intensively explored primarily as a consequence of th e history of
major flood control, navigation, nd water resources management projects by
th e U . S . Army Corps of Engineers. Consequently, much is known about geo-
morphic processes and the geotechnical properties of the deposits. Ironically,
however, th e alluvial valley is relatively poorly known from purely geologic
perspective, especially with regard to stratigraphy. Few studies of sedimentary
mechanics nd facies elationships have ever been undertaken.
Comparatively, th e deltaic plain ha s been much more extensively explored
than th e alluvial valley per se and s much better known in a geological sense.
T h a t knowledge is a direct consequence of several decades of intense investi-
gations by petroleum nd geophysical companies aimed at both better under-
standing th e Mississippi delta itself as well as the fundamental aspects of th e
occurrence and recovery of oi l an d ga s in large deltaic systems. A very large
percentage of th e numerous stratigraphic, petrologic, structural, paleontologic,
and chronologic studies that have been undertaken by universities and state
agencies have been funded directly or indirectly by the petroleum industry.
More recently, investigations of coastal and wetland processes relevant to
deltaic ecology and land loss processes have contributed valuable new geologic
data and concepts.
Intent and Scope of the Present Study
This volume is ntended s th e first comprehensive overview and synthesis
of th e geomorphology and geology of the Lower Mississippi Valley-both th e
alluvial valley and the deltaic plain-since 1944. However, it will vary from
that earlier classic work in several respects.
A primary difference is an attempt in th e present synthesis to present geo-
logical information and concepts to an audience of no t only engineers and
geologists bu t also scientists in a broad ange of disciplines. It is primarily a
document funded by and intended fo r the U.S. Anny Corps of Engineers, bu t
not just fo r the geotechnical, foundation design, potamology, nd similar
Chapte r Introduction
engineering functions of that organization. he synthesis also takes into con-
sideration th e informational needs of those concerned with such activities as
basin planning, environmental assessments and mitigation, and cultural and
natural resources management.
Engineering geology in its broadest context is th e appropriate category fo r
classifying this volume; however, it is not a "how-to" manual consisting of
unequivocal answers. either is it primarily a theoretical treatise focusing on
evaluating th e strengths and weaknesses of alternative hypotheses and para-
digms. he synthesis hopes to achieve a balance between th e tw o extremes by
presenting th e generally accepted concepts and also by providing a discussion
of th e degree of confidence in th e interpretations. t strives to separate pure
speculation and hypothesizing (which unfortunately is all that exists in some
cases) from that which is well founded nd scientifically tested. t does not
dwell on or attempt to resolve controversial issues.
Because of this approach, nd in comparison to th e emphatic and unequivo-
ca l nature of Fisk's 1944 study, some aspects of this volume m ay appear to be
a major step backward rather than an advancement of knowledge. hi s is
especially true with regard to th e chronological reconstructions. However, s
ha s been pointed out, th e earlier study attempted to present estimates that
are now regarded as being unjustified in detail and precision. he present
volume presents much less detail, bu t detail fo r which there is recognized
evidence.
T he organization and ection content of this volume involves some difficult
tradeoffs between logical order of discussion and data presentation and the
interests and backgrounds of the user audience. For example, th e decision to
separate discussions of mode of origin, lithology, nd geotechnical characteris-
tics of depositional environments into separate parts-not necessarily logical to
some-was done to accommodate th e different interests and needs of geologists
versus engineers. With a broadly multidisciplinary audience in mind, this
writer intentionally adopted a writing style comparable to that contained in
publications like American Scientist or Scientific American.
Geographically, this volume is estricted to the Lower Mississippi Valley
below the approximate latitude of Cape Girardeau, Missouri, and to the lower
reaches of its principal tributaries (Figure 1). Discussion and mapping is
limited to th e area downstream from Little Rock, Arkansas, on th e Arkansas
River, below Alexandria, Louisiana, on the R ed River, nd south of th e
Arkansas-Louisiana border on th e Ouachita River. Considerable information
on th e Quaternary geology exists for th e more upstream portions of those
rivers, and interested readers are referred to th e works by L.M. Smith (1986),
Smith and Russ (1974), nd Fleetwood (1969). Quaternary deposits and for-
mations above th e mouths of smaller tributaries re no t mapped and discussed,
bu t readers are referred to Saucier (1987) as an example of some of the infor-
mation that is available. he entire Mississippi River deltaic plain and a por-
tion of th e chenier plain in southwestern Louisiana ar e included in the scope of
this volume. Gould and McFarlan (1959) is the primary reference fo r
Chapte r Introduction
GULF OF MEXICO
30 0 KM
Figure . T he Mississippi alluvial valley, deltaic plain, and chenier plain, and the total distri-
bution of Quaternary deposi ts n the Lower Mississippi Val ley portion of th e Gulf
Coastal Plain
information on th e remainder (western portion) of the chenier plain. he dis-
cussion and mapping of th e deltaic plain are limited to th e subaerial portion of
that feature: Coleman (1988) nd Coleman and Roberts (1988) contain a sum-
m a r y of th e geology of th e offshore areas and subaqueous delta platform.
Quaternary deposits (fluvial terraces and related formations) of th e uplands
adjacent to th e alluvial valley are discussed in this volume; however, detailed
mapping is generally limited to narrow band flanking th e Holocene alluvial
plain.
T o avoid excessive length, readers are frequently referred to original
sources for specific detail nd documentation. or example, when radiocarbon
dates are discussed, complete citations with error limits, laboratory numbers,
precise locations, and similar data are intentionally not presented, even in
tabular form. t is believed that readers must be cognizant of all aspects of th e
dates, especially their specific contexts, to allow us e in future research or
interpretations.
Methods and Limitations
There are known extensive data gaps in the knowledge of the geomor-
phology and geology of th e Lower Mississippi Valley, bu t it was beyond th e
scope of this effort to undertake any field investigations or to develop any new
information. S o m e limited ne w interpretations are offered, bu t these relate to
resolving inconsistencies in existing data sets and th e problems normally
encountered when data from multiple sources and dates are synthesized into a
single, and sometimes ne w format.
It is acknowledged that because this writer initiated and conducted m a n y of
th e investigations on which this report is based and developed, it is heavily
flavored by hi s experiences and professional opinion. Hopefully, however, it
is not adversely biased or lacks objectivity. Where th e writer's opinion does
not reflect exposure to peer review or general acceptance, and where data from
hi s unpublished files are used, it is so acknowledged.
Subsurface nvestigations
Borings. or well over 10 0 years, it ha s been recognized that th e Missis-
sippi alluvial valley and deltaic plain are underlain by thick sequences of allu-
vial deposits. acking outcrops or bank exposures more than a few tens of
feet high, even before th e turn of th e century, scientists logically took keen
interest in samples from borings for clues to deltaic plain formation, and engi-
neers searched for answers as to the thickness and nature of th e deposits that
providing poor foundation and 1874,
1884; Wilson 1881).
Chapte r Introduction
Although the M R C took a pioneering role in th e engineering applications of
subsurface investigations, until th e 1930s m o s t data were generated as result
of water wells drilled fo r irrigation in th e alluvial valley area, and borings nd
wells drilled as part of petroleum exploration an d development in th e deltaic
plain area. More than five decades ago, Russell (1940) observed that th e Mis-
sissippi lluvial valley must be th e best explored thick alluvial sequence in th e
world. ince that time, th e amount of subsurface data available ha s increased
by orders of magnitude.
B y far th e largest collection of subsurface data on th e area exists in the files
of W E S . As part of th e more than 30-year effort to ystematically m ap th e
depositional environments of the Mississippi Valley, it ha s been standard prac-
tice to collect as much subsurface data as re practicably available. Routinely
surveyed sources include U . S . Army Engineer District offices, state highway
departments, th e U . S . Geological Survey groundwater division offices, the
U . S . Soil Conservation Service, private well drilling firms, petroleum com-
panies, consulting foundation engineering finns, and published eports. s
consequence of th e W E S mapping efforts for the Corps, the W E S files contain
data on an estimated 250,000 borings.
In amass ing these data, eldom ha s it been possible to examine actual cores
or samples. his generally ha s been possible only in terms of special projects,
such as Corps locks and dams, where detailed geologic investigations have
been involved. Rather, th e typical data used in the regional mapping effort
have consisted of descriptive driller's logs or laboratory logs and some geo-
technical test results.
Interpretations of subsurface