John W. Johnston Todd A.€¦ · J.P. (eds.), Tracking Environmental Change using Lake Sediments,...
Transcript of John W. Johnston Todd A.€¦ · J.P. (eds.), Tracking Environmental Change using Lake Sediments,...
Todd A. ThompsonAssistant Director for ResearchIndiana Geological SurveyIndiana University6 N h W l G
John W. JohnstonAssistant ProfessorDept. of Earth and Env. SciencesUniversity of Waterloo
U i i A W 611 North Walnut GroveBloomington, IN 47405‐2208Email: [email protected]: (812) 855‐4400
200 University Ave. W. Waterloo, Ontario N2L 3G1Email: [email protected]: (519) 888‐4567 ext. 33234
Outline to the dayOutline to the day18 AUGUST (Thursday) – Coastal Features and Deposits
8:00 – 9:00 Introduction to the Coastal Depositional System8:00 9:00 Introduction to the Coastal Depositional SystemControls on Shoreline SedimentationCoastal Processes and Littoral TransportShoreline BehaviorShoreline Features
9:00 – 10:00 Identification of Coastal Facies9:00 10:00 Identification of Coastal FaciesTypes and Characteristics
10:00 – 10:15 BREAK
10:15‐ 11:15 Coastal SequencesiTransgressive
Regressive/Aggradational
11:15 – 12:15 Chronostratigraphic TechniquesApplicationsShort‐lived vs. Long‐lived Isotopes (Cs137, Pb210 and C14) O i ll S i l d L i (OSL)
“The Fourth Dimension”Optically Stimulated Luminescence (OSL)
12:15 – 1:00 LUNCH while traveling to field site
1:00 – 6:00 Interpret Features in the FieldVisit Miller LookoutVisit modern Tiesma BeachVisit Platte Lake strandplain
“Accurate sediment
chronologies are of crucialg
importance in interpreting p p g
sedimentary archives.”yAppleby, P.G. (2001) Chronostratigraphic techniques in recent sediments. In Last, W.M. and Smol, J.P. (eds.), Tracking Environmental Change using Lake Sediments, Volume 1, Basin Analysis, Coring, and Chronological Techniques. Kluwer Academic Publishers, Dordrecht, pp. 171‐203.
Why is accurate dating important?To investigate: Timing of events, rates of change, correlation.
Need to… • Avoid contamination & understand stratigraphic context• Understand assumptions and limitations of dating procedure= realistic interpretation
Items to consider: Budget ‐ amount and quality? Site Selection – continuous record? Site Selection continuous record?Well preserved or disturbed? Retrieval? (dig, core‐vibrate,push,rotate) Suitable material? Suitable material?Multiple methods? Gaps or abrupt changes?
Two decades of age‐dating strandplainsLake SuperiorRadiocarbon & OSL
Lake HuronOSL
L k Mi hi
OSL
Lake MichiganRadiocarbon
Johnston and others (in press)
Two decades of age‐dating lake sediment
Slave River Delta (~40 sites)
Wolfe, B.B., Hall, R.I., Edwards, T.W.D., and Johnston, J.W., 2012, Johnston, J.W., 2012, Developing temporal hydroecologicalperspectives to inform stewardship of a northern floodplain landscape subject to multiple
Peace‐AthabascaRiver Delta (~60 sites)
j pstressors: paleolimnologicalinvestigations of the Peace‐Athabasca Delta, Environmental Reviews 20 191‐210
Lateral and Vertical Chronosequences
VerticalVerticalStratigraphy
Lateral Chronosequence
YoungestShallow
http://kingfish.coastal.edu http://sepmstrata.org
OldestYoungestOldest Lakeward LandwardDeep
Reconstructing Lake Level from ancient shorelines & coastal wetlands
Lake Athabasca PaleohydrographMackenzie y g p
a) Ancient shoreline and wetland.
Johnston et al. The Holocene (2010)http://hol.sagepub.com/content/20/5/801.abstract
Wolfe et al. Geophysical Research Letters (2011)http://www.agu.org/pubs/crossref/2011/2011GL047599.shtml
Lakes Superior, Michigan & Huron PaleohydrographsGreat Lakes
Wolfe et al. Environmental Reviews (2012)http://www.nrcresearchpress.com/doi/full/10.1139/a2012‐008#.UJsv_Wez6yM
) O A i Sh lia) One Ancient Shoreline
b) 30 to 80 Ancient Shorelines in a Strandplain
c) Many Strandplains around lake basin
MICHIGAN B dk & Th J l f G L k R h ( )
MN
Lake Superior
Th
GrandTraverse
BayTahquameno
Au TrainBay
Batcha
S
SUPERIOR ‐ Johnston et al. Canadian Journal of Earth Sciences (2012)http://www.nrcresearchpress.com/doi/abs/10.1139/e2012‐057#.UJssQmez6yMHuron – (in prep.)
MICHIGAN ‐ Baedke & Thompson Journal of Great Lakes Research (2000)http://www.sciencedirect.com/science/article/pii/S0380133000707052
Principle Dating MethodsRate of atomic disintegration in a sample or
Growth of an organisms to date the substrate on p
surrounding environment.
the substrate on which it is found.
(Used for correlation)Past reversals of Earth’s magnetic field & their effects on a sample.
Time‐dependent chemical Bradley (2014) Paleoclimatology: Reconstructing Climates of the Quaternary, Academic Press, 696 p.
Time dependent chemical Changes in sample or chemical characteristics of sample.
Radioisotopic Dating Methods
Radioactive Isotope
Atoms of the same element can have different numbers of neutrons.
Unstable atoms decay or disintegrate spontaneously at predictable and measureable ratesmeasureable rates. Carbon‐12 (126C)
• 6 protons, 6 neutrons, mass 12Carbon‐13 (136C)
• 6 protons 7 neutrons mass 13
www.nrc.gov
• 6 protons, 7 neutrons, mass 13Carbon‐14 (146C)
• 6 protons, 8 neutrons, mass 14
Lead‐210 (210Pb) Dating Luminescence (OSL) Dating
Radiocarbon (14C) Dating
Can we differentiate these three?Lead‐210 (210Pb) Dating The degree to which members of a chain of radioactive decay are
d ilib i f ll i i i i l l b i
Temporal range of each?
restored to equilibrium following some initial external perturbation. Approx. 150 years (half‐life of 210Pb = 22 years) Fine‐grained sediment (210Pb: source ‐ transport ‐ deposition)
Radiocarbon (14C) Dating The quantity of a radioisotope as a fraction of a presumed initial level. (h lf l f f )
Type of sediment?
Luminescence (OSL) Dating
Approx. 40,000 years (half‐life of 14C = 5568 years) Any material which is composed of carbon may be dated.
( ) g The integrated effects of some local radioactive process on the
sample material, compared to the value of the local (env.) flux. A ( i ) Approx. 200,000 years (near saturation) Principle minerals used are quartz and feldspar. (fine silt to med. sand)
Half‐life and Radioactive decayHalf life and Radioactive decayUnstable atoms decay or ydisintegrate spontaneously at predictable and measureablerates
14C (t1/2 = 5568 years)
rates.
210Pb (t1/2 = 22 years)
How does 210Pb get to our sediments? Th d f R ( d ) f ll i h d f 6R ( di ) [ 8U d i ] The decay of 222Rn (radon), following the decay of 226Ra (radium) [238U decay series] Both 222Rn and 226Ra escape from Earth’s surface and enter the atmosphere. The stratigraphic distribution of unsupported 210Pb (the dominant 210Pb supply to
l k ) l k d b d bl h l f l k dlakes) in lake sediments can be used to establish a timescale for lake sediments. Total 210Pb activity in sediment = supported + unsupported.
Unsupported:Unsupported:From atmospheric flux• washed out = precip.• settles out = dry falloutsettles out = dry fallout
Supported:From in situ decay of the parent radionuclide 226Ra (radium)
T 22 years (210Pb)
(When supported and unsupported 210Pb are in equilibrium, background 210Pb has been reached)
T1/2 = 22 years (210Pb)to stable 206Pb
Bradley Paleoclimatology
Estimate of Background Depth(Where Total 210Pb = Supported 210Pb or Unsupported 210Pb = 0)
J F B 4 30
(Where Total 210Pb = Supported 210Pb or Unsupported 210Pb = 0)
h (c
m)
1
2
Dep
th
3
4
T o ta l 2 1 0 P b2 2 6 R a
A c t iv i t y ( d p m /g )
1 1 05
We now have an inference of “background depth” where Total 210Pb = Supported 210Pb. We have directly measured the Total 210Pb for each slice and with our measured
Supported 210Pb we can calculate Unsupported 210Pb for each core slice down to background depth as: Unsupported 210Pb = Total 210Pb ‐ Supported 210Pb
From sediments to a 210Pb chronology
How many samples?
Age Model
Height of artificial fallout from
l Equilibrium:Unsupported
Smol (2008) Pollution of Lakes and Rivers: a Paleoenvironmental Perspective
nuclear weapons tests
UnsupportedSupported
Height of
137CsTime MarkersHeight of artificial fallout from nuclear weapons tests(1963 CE)
What should the characteristics of good ti k b ? ( 9 3 )time markers be?
1. Instantaneous2. widespread 1963‐64 (Bomb‐test peak, Global fallout) 1986 (Chernobyl, mostly Europe) 2011? (Fukushima, Mostly Japan and region?)2. widespread3. distinctive
What are some examples of potentially good time markers?
volcanic deposits magnetic events catastrophic e ents
good time markers?
catastrophic events (floods, pollution, land use)
Human events Bradley Paleoclimatology
210Pb Dating fi i l i t d di t t ( l) confirming laminated sediments are true varves (annual) confirming core‐tops are undisturbed calibrate with instrumental records to develop accurate transfer
functions for paleo reconstructionsfunctions for paleo‐reconstructions
Sinnatamby et. al. (2010) Historical and paleolimnologicalp gevidence for expansion of Lake Athabasca (Canada) during the Little Ice Age. J Paleolimnology.
Peace‐Athabasca Delta
Appleby (2001) Chronostratigraphic techniques n di I L d S l ( d ) T ki recent sediment, In Last and Smol (eds) Tracking
environmental change using lake sediments, volume 1: Basin analysis, coring, and chronological techniques.
B. Wolfe
14C: Formation, Di l & D
Where?• C14 is constantly forming in the
h Dispersal, & Decay upper atmosphere. How Form?
• When a high‐energy neutron( f ) k(a type of cosmic ray) strikes a N14 atom, it may be absorbedby the nucleus and eject a proton, changing it to C14.
Rate of Formation?• fairly constant and has been
calibrated against tree rings.
• All carbons are absorbed in a nearly constant ratio by all nearly constant ratio by all living organisms.
• When an organism dies, C14 is not replenished and the ratio not replenished and the ratio of C14 to C12 decreases.
• C14 dating uses the C14/C12 ratio ofmaterial that was once living, clockstarts when an organism dies. Half‐life: T1/2 = 5568 years (14C)
From sediments to a radiocarbon age
Conventional / AMS 14C DatingConventional / AMS C Dating small amounts selected fractions of sediment better time resolution better time resolution
Bjork & Wohlfarth (2001), 14C ChronostratigraphicTechniques in Paleolimnology, In Last & Smol, Tracking Env. Change using lake sediment V1.
Calibration 6000
7000Calibration databaseIntCal13 Reimer et al. (2013)Radiocarbon 55: 1869‐1887
3000
4000
5000
arbo
n ag
e BP
calibrated
uncalibrated (1:1)
“present”
Radiocarbon 55: 1869‐1887.
Radiocarbon Age1000±50
1000
2000
3000
Rad
ioca present
1950 CE
Calibration programs:• CALIB / Oxcal / CalPal
00 1000 2000 3000 4000 5000 6000 7000
Calendar year BP
Intercept &Probability
Radiocarbon AgeRadiocarbon Age4000±80
One Sigma Ranges: [start:end] relative area
One Sigma Ranges: [start:end] relative area[cal BP 801: cal BP 812] 0.072[cal BP 828: cal BP 862] 0.276 g g [ ]
[cal BP 4299: cal BP 4327] 0.071[cal BP 4353: cal BP 4369] 0.040[cal BP 4386: cal BP 4582] 0.0849[cal BP 4603: cal BP 4606] 0.009[cal BP 4769: cal BP 4781] 0.031
Two Sigma Ranges: [start:end] relative area[ l BP l BP ]
[ ] 7[cal BP 903: cal BP 963] 0.652
Two Sigma Ranges: [start:end] relative area[cal BP 789: cal BP 988] 0.977[cal BP 1030: cal BP 1048] 0.023
[cal BP 4237: cal BP 4709] 0.934[cal BP 4754: cal BP 4813] 0.066
Depositional Lag Times & Sample ContaminationDoes the final reworking and transportation take place fairly soon after death?Is there a connection between event being dated and the startof the radiocative decay process (the “clock”)
Can you see evidence of reworking?
(the clock )
Bjork & Wohlfarth (2001), In Last & Smol, Tracking Env. Change using lake sediment V1.
http://geology.tufts.edu/varves/Geology/dating.asp
Radiocarbon Dating
Used throughout the world
many different types of samples used for dating
covers a time period of major, global env. change
invaluable in archaeological studiesg
Radiocarbon and OSL (Paleohydrograph Age)Radiocarbon & OSL
4000
4500
C14
Modified from:Argyilan et al.
2500
3000
3500
ars
befo
re 1
950
C14OSL
QuaternaryResearch(2005)
1000
1500
2000
Cal
enda
r yea
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
Distance from modern shoreline (m)
0
500
Optically Stimulated Luminescence (OSL)
• Age of Burial• Quartz or FldsprQ p• Imperfections in crystallattice, able to storeionizing energy (trap)ionizing energy (trap)
• Absorb radiation• Surrounding decay(235U, 238U, 232Th, 40K, 87Rb)
• Energy released (reset) if http://core.ecu.edu/geology/mallinsond/OSL.htm
gy ( )exposed to sunlight or heat)
Dr. K. Lepper, North Dakota State Universityhttp://crustal usgs gov/laboratories/luminescence dating/what is tl htmlhttp://crustal.usgs.gov/laboratories/luminescence_dating/what_is_tl.html
OSL dating repeated and/or lengthy light exposure
Partial bleaching of grains
Cores vs. Soil PitsPartial bleaching of grains during burial, mixing of grains by bioturbation, and pedogenic (soil formation) processes can alter the dose rate over time. The largest uncertainty in the dose
rate calculation is commonly associated with water content.
Rhodes (2011) Optically stimulated luminescence dating of sediments over the past 200,000 years, Annual review of earth and planetary sciences 39 (1) 461 ‐488.
QuestionsQuestions… Can you name and differentiate the
three radioisotopic dating methods
Do I always need to go
three radioisotopic dating methods I mentioned in this talk?
y gdeeper to obtain older sediments or landforms?
Items to consider: Budget ‐ amount and quality? Site Selection continuous record? Site Selection – continuous record?Well preserved or disturbed? Retrieval? (dig, core‐vibrate,push,rotate) Suitable material? Preparation? Suitable material? Preparation?Multiple methods? Gaps or abrupt changes?
Useful References• Tracking Environmental Change Using Lake Sediments (DPER Volume 1 to 5)
• Appleby, P.G. (2001) Chronostratigraphic techniques in recent sediments. In DPER, Volume 1, Basin Analysis, Coring, and Chronological Techniques, pp. 171‐203.
• Blaauw M and Heegaard 2012 Estimation of Age Depth Relationships In Birks • Blaauw, M. and Heegaard, 2012, Estimation of Age‐Depth Relationships, In Birks, H.J., Lotter, A.F., Juggins, S., Smol, J.P. (eds) Tracking Environmental Change Using Lake Sediments Developments in Paleoenvironmental Research Volume 5, pp 379‐413.
• Rhodes (2011) Optically stimulated luminescence dating of sediments over the past y g200,000 years, Annual review of earth and planetary sciences 39 (1) 461 ‐488.
• Sanchez‐Cabeza & Ruiz‐Fernandez (2012) 210Pb sediment radiochronology: An integrated formulation and classification of dating models. Geochimica et Cosmochimica Acta 82: 183–200.
• CALIB (Stuiver and Reimer 1993: http://www.calib.org), BCal (Buck et al. 1999: http://bcal.shef.ac.uk), and OxCal (Bronk Ramsey 2007: https://c14.arch.ox.ac.uk/oxcal)
• Argyilan, E.P., Forman, S.L., Johnston, J.W., 2005, Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan USA, Quaternary Research, v. 63, p. 122‐135.
• Bradley (2014) Paleoclimatology: Reconstructing Climates of the Quaternary, Academic Press, 696 p.• Johnston. J.W., Thompson, T.A., and Wilcox, D.A. (in press) Paleohydrographic reconstructions from
strandplains of beach ridges in the Laurentian Great Lakes, in Martini, I. P., and Wanless, H. R., d S di t C t l Z f Hi h t L L tit d Si il iti d Diff G l i l eds., Sedimentary Coastal Zones from High to Low Latitudes: Similarities and Differences: Geological Society, London, Special Publications, 388.
• Smol, J.P. 2008. Pollution of Lakes and Rivers: A Paleoenvironmental Perspective. 2nd edition. Wiley‐Blackwell Publishing, Oxford. 383 pp.
http://www.glerl.noaa.gov/data/now/wlevels/dbd/
Baedke and |Thompson (2000) & Johnston and others (2012)