land sea correlations: pitfalls and remedies · issues . 1. are land – sea and land-land...
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LAND SEA CORRELATIONS: PITFALLS AND REMEDIES
ASHOK KUMAR SINGHVI Physical Research Laboratory
Ahmedabad, India
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WELCOME TO INDIA Besides Science,
Do Savor Our Culture – Cuisine –Traffic - Warmth
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Geo-science: The Basic Science for a Sustainable Future
INTERNATIONAL GEOLOGICAL CONGRESS DELHI, FEB 23-29, 2020
CO-HOSTED BY BANGLADESH – NEPAL - PAKISTAN - SRILANKA
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Issues 1. Are LAND – SEA and LAND-LAND correlations Correct
2. Are the inferred periodicities in terrestrial records correct
3. Are proxies interpreted along with their response times/thresholds
4. Are tele-connections correct, sensu stricto
5. Do we understand land records their climatic implications
Do we really have
Secured Chronologies and Proxy interpretations for model validations ?
Stating the Obvious & Overstating it to Ensure Caution
LAND SEA CORRELATIONS: PITFALL AND REMEDIES
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Geological Correlation using tuning are like Seven-league boots approach of Near Instant travel (Response) over long distances.
But this does not happen in nature. Using these one is lead to a trap of a
“Coherent Myth” or “Reinforcment syndrome” Oldfield2001,Blaauw, 2012
Would the paleoclimate science not be boring, should this be so
Kilimanjaro : a case
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Earth Science Reviews 2001
Quaternary Science Reviews 2012
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Precise Age Precise Variable
Age with Error Variable with error Threshold + lags + Variable response time
Precise Age Variable with Error
Serious ISSUES on both CHRONOLOGY AND PROXIES
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Chronologies on terrestrial sequences are based on:
Radiocarbon Range ~40ka, precision ⇑, calibration, organics, diagenesis, contamination, reservoir ages variable with in a lake, sample-strata correlation, Uranium Series Range 300ka, no calibration, precision ⇑, pure carbonate phases, detrital contamination reduces precision and accuracy
Cosmogenic Isotopes Range ~ Few ka-Ma, needs inputs on irradiation geometry and constancy of the same, not good for accreting soft sediments
Luminescence Dating Range Present –few hundred ka –Ma, sample –strata correlation clean, precision ~ 5%
Paleomagnetism Relative dating
Records tuned with MIS or GRIP or orbital – Double tuning for terrestrial records
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Mischke et al, 2013 (in press)
Intra Lake Variability In radiocarbon Reservoir ages And Its variability with time
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Proxies Grain size
Carbonates Magnetic Susceptibility
Stable isotopes diatoms
Foraminifera Geochemical changes Pollen Phytoliths Alkenones ………
In tuning the proxy records, It is implicitly assumed that all respond to a Global forcing instantaneously and remain in phase, and that their response has been time invariant, without any thresholds. In contrast,
NULL HYPOTHESIS : PROXIES ARE NOT CORRELATED Why should Solar Forcing be seen in records;
Each record should have a independently distilled response
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Sucking In
Smearing out
Tie Point ↔ 5-10ka
Time Lines
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Loess-Paleosol sequences
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Kukla, 1986
Xifeng, China Magnetic Susceptibility
tuned to oceanic record
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Maher and Thomson, 1992
“…extremely high correlation with the standard 18O record” S
PE
CM
AP
TIM
E S
CA
LE X
1000
yea
rs
18δO Log Susceptibility Luochuan
S1
S2
Loess –Paleosol sequences Considered to be the terrestrial analogs of marine records
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Vandenberghe et al., 1997 U ratio – 44-16µm/16-5µm
Grain Size records also seen to be covariant
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Porter and An. Science
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Deduction of Milankovitch periodicities based on Ages assignments using inferred ages for the loess/paleosol layers
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Some of the Obvious Difficulties B/M boundary : In Marine Records is in Stage 19 (warmer), but in loess layer L8 (cooler) - missing time!
Freezing time of magnetization in loess – few ka ? what is being correlated
In Alaska, Magnetic susceptibility is out of phase with China (high in loess and low in paleosols) Grain-size vs. Soil phase lagged Singhvi et al., Earth Sci. Revs,2001
Zhao and Schakelton, EPSL,1999
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Grain Size
Carbonate content 0.8m 5-10 ka Vandenberghe, 2012
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EPISODIC ACCUMULATION & LONG HIATUSES
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EPISODIC ACCUMULATION & LONG HIATUSES
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Stevens – INQUA 2011 How does one compare these with Ocean and Ice cores with constant accumulation rates ?
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S0 Loess-Soil
S1 Soil-Loess
Drier- Wetter
So
S1 In Xian Soil till 75ka
Soil
Soil
Soil
Singhvi et al. Earth Sci Revs
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Ashok Singhvi DESERTS
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Limits of Active dunes at LGM, Holocene and Present
Sarnthein ,1982 Synchronous expansion and contraction
ALBEDO CHANGES IN THE PASTPAST
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330mm/a 200mm/a
Singhvi etal QSR; Dhir et al JASc
Aeolian system Response Phase Lagged and Episodic
We see a preservation record And not An aggradation/dynamism record
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Age of linear dunes
Majority of data is by PRL and this data shows that different deserts responded differently.
Aeolian aggradation in Deserts was not synchronous -peaking at LGM
LGM India
Modified after Lancaster, 2004
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Limits of Active dunes at LGM, Holocene and Present
Sarnthein ,1982
Synchronous expansion and contraction
Not tenable – needs a change
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0 200
Km
SutlejRavi
Indu
s R
SULAIMAN RANGE
ALLUVIAL FANS OF HIMALAYAN RIVERS
Sabarmat R
.
Ganga R
Jamuna R
DELHI
KUTCH
SAURASHTRA
AHMEDABAD
30O
90O
30O
76O70O
KARACHI
10ka
5ka
4ka
3ka
1ka
Dune Sand (Thar)Southern Desert MarginMarshy area (Rann)
SEMI-ARIDARID
ARABIAN SEA Progressive SHIFTING OF Active Dune limits From 10 to 1ka.
Shrinking Desert
800a 400a
Active/Fossil Dune Limit
Juyal et al. 2006
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ka B.P.
0
4
8
12
16
20
LEGEND
West (<200 mm) East (330 mm)
Thar Desert
12
6
4.8
7
9.4
12
4.5
7
21
North-west (250 mm)
Ephemeral (present condition)
Lake high
Fluctuating with extremes
Fluctuating without extremes
Hypersaline
(Kanod and Bap-Malar) (Lunkaransar) (Didwana)
10
15.5
East (500 mm)
(Sambhar)
4.5
7-8
Fluvially reworked
aeolian sediments
10
15.5
Fluvially reworked
aeolian sediments
3.5
Spatial Heterogeneity of records- MONSOON VARIED DURING THE HOLOCENE
• >9ka -7ka • 7ka - 4.8ka
• < 4.5 ka
400km
THAR DESERT
(Roy et al,2009)
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From RC-2735 box cores
Composite
Temperature variationG. Bulloides
From RC-2730 box cores
Anderson et al., 2002
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Sple
othe
m re
cord
Floo
d re
cord
(Lun
i R)
Dun
e re
cord
2500
2250
2000
1750
1500
1250
1000
800
600
500
450
400
350
300
250
200
150
100
50
Bre
aded
seq
uenc
e
Ove
rban
k an
d flo
od s
eque
nce
Pond
seq
uenc
e
Aeo
lian
sand
Pond
seq
uenc
eFl
ood
plai
n
Wet humid
Fluctuating
Fluctuating
Semi- arid
Arid/Semi arid
Semi- arid
Semi- arid
Wet Humid
Semi-arid
Year
BP
0
500
400
300
200
100
0
1000
800
600
6 4 2 0
(1) Yadav and Ramesh, 2001(2) Anderson et al, 2003
(1)
(2)
(Yea
r BP)
Monsoon Winds And G Bulloides ; Vs. Spatial Heterogeneity of Rainfall
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Kocurek, 1999
Creation of a terrestrial sedimentary record in non-trivial
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My submission (possibly obvious to many)
• Creation of Sedimentary record on land needs a Window of Opportunity based on Sediment Supply, Transport and Preservation
• Sediment supply in terrestrial domain is invariably, variable • Preservation in transitional climates. Only the Preserved Record seen. • Spatial variability: Local vs. regional factors; Chronology • In correlations, response time of proxy is necessary; mostly ignored • Causal mechanism for correlation between land – ice and land – sea
is needed ? Why should changes in marine forams or grain size in loess be synchronous ?
• Secured chronology should only basis- role of systematic errors (reservoir ages), base lines.
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Need to Revisit All records where correlations and periodicities
are established WITHOUT due recognition of CAUSAL mechanism and DETAILED chronology
THIS IS
AN INCONVENIENT TRUTH
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Systems Dynamics Approach Stocks and Flows with feedbacks and delays
Xiaojing Zheng, 2011, Wasson ,2012
Needs to relook at Proxy Response- thresholds and time scales Improve Chronologies – methods and what is being dated For realistic Future EARTH scenarios
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First, Get your facts straight, and then,
You can twist them as much as you want.. Mark Twain
Nature is complex and will keep its secrets
THANKS, I rest my case here.
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Realizing these limitations of reason and scientific method…
it is better to understand a part of truth and apply it in our lives,
than to understand nothing at all and flounder helplessly…
“There is no visible limit to the advance of science…”