Chemostratigraphic Trends of the Middle Devonian Marcellus Shale, Appalachian Basin - Preliminary...

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Chemostratigraphic Trends of the Middle Devonian Marcellus Shale, Appalachian Basin: Preliminary

Observations*

Gary G. Lash1

and Randy Blood2

Search and Discovery Article #80198 (2011)Posted October 31, 2011

*Adapted from oral presentation at AAPG Eastern Section Meeting, Washington, D.C., USA, September 25-27, 2011

1Dept. of Geosciences, SUNY Fredonia, Fredonia, NY, 14063 ([email protected])2Randy Blood, EQT Production, Pittsburgh, PA, 15222

Abstract

Trace element and metals abundances have been used to elucidate the hydrography of silled basins as well as watermass chemistry anddeepwater residence times. The database of our preliminary study of the Middle Devonian Marcellus Shale comprises chemostratigraphic

(Xray fluorescence) elemental concentrations determined from cores recovered from eastern New York, southwest Pennsylvania, and

northern West Virginia. Regional covariance trends of authigenic molybdenum (Moauth) and uranium (Uauth) and their respective enrichment

factors (EFs) define a uniform (Mo/U) auth ratio of 2 3 times the Mo/U molar ratio of seawater. Moauth is enriched relative to Uauth by a

factor of 5:1 to 10:1, suggesting accelerated transport of Mo to the seafloor by a particulate (Mn) transport mechanism that would have

required frequent fluctuations between suboxic and moderately sulfidic water column conditions. Indeed, the relationship of total organiccarbon and Mo(ppm) in eastern New York suggests water renewal times on the order of several hundred years. A data subset defined by

diminishing Moauth and Uauth EFs at reduced aqueous Mo/U ratios may reflect the preferential uptake of U under largely suboxic conditions.

Moreover, data from a well in northern West Virginia defines Mo auth and Uauth values typical of bottom water depleted in Mo (Mo/U = 0.1 0.3 x seawater) and (Mo/U) auth ratios of 1:1. Thus, whereas the Marcellus basin may have experienced frequent episodes of suboxic tosulfidic conditions that accelerated Mo enrichment, local hydrographic conditions (i.e., stronger degree of water column stratification)appear to have favored Mo drawdown in bottom water. Equally intriguing is the regional concentration of barium in the upper part of the

Marcellus, which may reflect an episode of enhanced paleoproductivity at this time. Further, chloride and strontium are especiallyconcentrated in transgresive systems-tract deposits, perhaps reflecting salinity excursions that could have enhanced the preservation of

organic matter in these intervals.

References

Algeo, T.J., and N. Tribovillard, 2009, Environmental analysis of paleoceanographic systems based on molybdenum-uranium covariation:

Chemical Geology, v. 268/3-4, p. 211-225.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


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Blauch, M., N. Houston, M. Seyman, and R. Reese, 2009, Technique reuses frac water in shale: American Oil and Gas Reporter, v. 52/9, p.

103-107.

Smith, C.N., and A. Malicse, 2010, Rapid Handheld X-Ray Flourescence (HHXRF) Analysis of Gas Shales: AAPG Search and Discovery

Abstract #90108. Web accessed 24 October 2011,http://www.searchanddiscovery.com/abstracts/pdf/2010/intl/abstracts/ndx_smith.pdf

Taylor, S.R., and S.M. McLennan, 1985, The Continental Crust: Its Composition and Evolution: Blackwell, Oxford, England, 312 p.

Wedepohl, K.H., 1971, Environmental influences on the chemical composition of shales and clays, in L.H. Ahrens, F. Press, S.K. Runcorn,

and H.C. Urey, (Eds.) Physics and Chemistry of the Earth: Oxford (Pergamon) Press, Oxford, England, v. 8, p. 307-331.

Wedepohl, K.H., 1991, The composition of the upper earths crust and the natural cycles of selected metals: metals in natural raw materials;

natural resources, in E. Merian, (Ed.), Metals and their Compounds in the Natural Environment: Weinhein (VCH-Verlagsges), Germany, p.

3-17.

Website

Blakey; R., 2011, North American Paleogeography: Web accessed October 14, 2011,http://www2.nau.edu/rcb7/namD385.jpg
http://www.searchanddiscovery.com/abstracts/pdf/2010/intl/abstracts/ndx_smith.pdfhttp://www.searchanddiscovery.com/abstracts/pdf/2010/intl/abstracts/ndx_smith.pdfhttp://www2.nau.edu/rcb7/namD385.jpghttp://www2.nau.edu/rcb7/namD385.jpghttp://www2.nau.edu/rcb7/namD385.jpghttp://www2.nau.edu/rcb7/namD385.jpghttp://www.searchanddiscovery.com/abstracts/pdf/2010/intl/abstracts/ndx_smith.pdf


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Chemostratigraphic trends of the Middle Devonian

Marcellus Shale, Appalachian Basin: premliminary

observations

Gary G. Lash,

Dept. of Geosciences,

SUNY Fredonia,

Fredonia, NY, 14063

Randy Blood,

Pure Earth Resources,

New Brighton, PA 15222


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chemostratigraphy - especially suited to the study of fine-grained,seemingly homogenous (biostratigraphically barren) deposits

variations in elemental abundances reflect changes in suchparameters as paleoclimate, hydrographic aspects of the

paleocean, paleoredox conditions (including oceanic anoxic

events), and mineralogy

Introduction

high resolution correlation of cm-scale units


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handheld XRF (HHXRF) analyzer Thermo Scientific Niton XL3t 950 GOLDD+equipped with a silicon drift detector

Smith and Malicse (2010)

comparison of HHXRF technology with

results obtained via independent

laboratory ICP-MS methodology

160 sedimentary rock samples of mixed

lithology

hand (outcrop) samples, core, cuttings

analytical approach


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Mo y = 1.1531x - 4.124R

2= 0.9834

0

2040

60

80

100

120

140

160

0 20 40 60 80 100 120 140

NITON XRF, Mo (ppm)

Labora

toryICP,

Mo(ppm)

Cr y = 0.98x + 0.33R

2= 0.7414

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

NITON XRF, Cr (ppm)

LaboratoryICP,

Cr(ppm)

Fe2O3y = 1.0616x - 0.1812

R2

= 0.9946

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0

NITON XRF, Fe2O3 (wt%)

a

oratory

,

e

(wt%)

Al2O3y = 0.9541x + 0.1399

R2 = 0.9754

0

2

4

6

8

10

12

1416

18

20

0 2 4 6 8 10 12 14 16 18 20

NITON XRF, Al2O3 (wt%)

a

oraory

,

w

TiO2 y = 1.1502x + 0.0038R2 = 0.9668

0

0.2

0.4

0.6

0.8

1

0.0 0.2 0.4 0.6 0.8

NITON XRF, TiO2 (wt%)

La

bora

tory

ICP

,TiO2(wt%)

V y = 0.5044x - 14.246R

2= 0.834

0

100

200

300

400

500

600

0 200 400 600 800 1000

NITON XRF, V ppm

La

bora

ory

ICP

,V(ppm

) SiO2 y = 0.8824x - 0.4214R

2= 0.9702

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

NITON XRF , SiO2 (wt%)

La

bora

to

ryICP

,SiO2(wt%)

CaOy = 0.7828x + 1.8304

R2

= 0.9967

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70

NITON XRF, CaO (wt%)

a

ora

tory

,

a

(wt%

)

MnO

y = 0.9201x + 0.0008

R2 = 0.843

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.000 0.010 0.020 0.030 0.040 0.050 0.060 0.070

NITON XRF, MnO (wt%)

La

bora

tory

ICP

,M

nO

(wt%)


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very strong correlations (r2 > 0.90) with laboratory

ICP-MS data for most major, minor and trace elements from

Mg to U

differences in data sets can arise from the sample

preparation procedure employed by labs versus the direct

measurement in situ by HHXRF

HHXRF analysis is non-destructive and enables one to

readily analyze on a cm-scale.analysis of Marcellus cores at ~2.5 3 cm intervals


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clastic signature

%Al - a proxy for clay

general observations

r=0.92


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Zr clastic source

r=0.82


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clastic trend

deficient Si

excess Si


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quartz (authigenic; closely associated with organic matter)

pervasive throughout a matrix deficient in clay

ca

qtz

om


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0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50 60 70

TOC(wt%)

QUARTZ

r=.66

transgressive systemstract deposits

TOC vs. quartz


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Marce

llus

Shale

Union

Springs

Oatka

Creek

CV

TST

TST

RST

RST

OnondagaLs.


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Mo and U

redox sensitive metals especially useful for paleoenvironmental and

hydrographic studies

--present in low concentrations in the upper crust

- Mo ~ 3.7 ppm

- U ~ 2.7 ppm (Taylor and McLennan, 1985)

--both exhibit conservative behavior under oxic conditions;

--both elements have long residence times in seawater-

-Mo ~ 0.78 MY

-U ~ 0.45 MY

--both exhibit roughly equal concentrations in seawater globally:

Mo/U = 7.53 molar ratio Pacific Ocean

Mo/U = 7.90 molar ratio Atlantic Ocean

--both exhibit low concentrations in plankton enrichment in sediment

can be related to authigenic uptake from seawater;


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significant differences

U uptake is linked to organic carbon content (TOC) and occurs

by diffusion across the sediment-water interface (i.e., within the sediment)organic matter serves as a sorbentsedimentation rate is very

important to this

Mo uptake by sediment requires the presence of H2S (euxinic conditions)

and can be accelerated by particulate Mn-Fe-oxyhydroxide shuttle (U isunaffected by this); less covariance with TOCunlike U


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Algeo and Tribovillard, 2009

EF = enrichment factorelemental abundance

Mo/U molar ratiosrelative to seawater


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EF = enrichment factor

"""" averageaverage

samplesample

Alelement

Alelement

average shale values from Wedepohl (1971, 1991)


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basin margin

progressive enrichment of U relative to Mo

as total authigenic enrichment increases


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evolving water mass chemistry

Mo depleted water mass

restricted basin


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considerable enrichment of Mo relative to U

Mo/U ~ 5 x SW


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Mn (Fe)-oxyhydroxide particulate shuttle (continuous

scavenging)

adsorbed molybdate

requirement intermittently sulfidic (dissolved H2S) bottom waters

weakly restricted basin

f ( f )


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progressively higher abundances of U (in excess of Mo)

and eventually enrichment of Mo relative to U

continental margin sites


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increasingly reducing conditions

chemocline

euxinicanoxic

weakly restricted to open marine


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Chenango Cty, NY


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Greene County, PA


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Wetzel County, WVA


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Algeo and Tribovillard, 2009 strong relative enrichmentof Mo relative to U

operation of a particulate shuttle mechanism that

enhanced transfer of Mo to the seafloor

frequent redox fluctuations


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fossild

ebris

b

ioturbateddark-

grayshale

shoaling redox boundary

diminished bioturbation;

increased uranium

frequent redox fluctuations

t h ith th l b l Rh i O


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Middle Devonian

Ron Blakey; http://www2.nau.edu/rcb7/globaltext2.html

Rheic Ocean

water mass exchange with the global Rheic Ocean


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Doddridge Cty, WVA

lower EFs and diminished Mo/U

preferential uptake of U over Mo under largely

suboxic to anoxic conditions


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Upshur Cty, WVA

U more enriched than Mo

Mo/U substantially less than seawater


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Ron Blakey; http://www2.nau.edu/rcb7/globaltext2.html

Rheic Ocean

isolation from the Rheic Ocean and

consequent depletion of Mo relative to

U

M ll Sh l th t P l i


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Marcellus Shale, southwestern Pennsylvania

salt described from Marcellus cores;

Blauch et al., 2009autochthonous salt described from

Marcellus cores; Blauch et al., 2009

elevated chlorideelevated chloride


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calcite-filled vertical fracture

carbonate concretion

halite


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Bennett well

Sullivan County, PA

courtesy Chris Laughrey


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Marcellus Shale, northern

central West Virginia

enriched Cl associated with TST

deposits at the base of the Marcellusenriched Cl associated with TST

deposits at the base of the Marcellus


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Conclusions

-covariance of Mo and U in the Marcellus is consistent with a

particulate shuttle as a means of accelerating Mo transport tothe sea floor;

-the particulate shuttle requires a threshold level of H2S in the

water column (euxinic conditions) to activate the Mo;

-fluctuation of the chemocline (necessary for particulate shuttle)

may have been aided by episodic introduction of seawater

from the global (tropical or Rheic) ocean as a means of

replenishing Mo and U;

-the locally silled nature of the Marcellus basin is suggested by

the presence of diminished Mo enrichment relative to U;


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Conclusions

-sulfidic conditions and enhanced organic matter enrichment

of the lower Marcellus Shale (Union Springs) may have beenaided by the early influx of saline shelf waters produced as a

consequence of the initial Marcellus transgression (perhaps

one causal mechanism for the Middle Devonian (late Eifelian

- Union Springs) Kak Event or earlier Bakoven bioevent


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Chemostratigraphic Trends of the Middle Devonian Marcellus Shale, Appalachian Basin - Preliminary...

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