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LAND SEA CORRELATIONS: PITFALLS AND REMEDIES
ASHOK KUMAR SINGHVI Physical Research Laboratory
Ahmedabad, India
WELCOME TO INDIA Besides Science,
Do Savor Our Culture – Cuisine –Traffic - Warmth
Geo-science: The Basic Science for a Sustainable Future
INTERNATIONAL GEOLOGICAL CONGRESS DELHI, FEB 23-29, 2020
CO-HOSTED BY BANGLADESH – NEPAL - PAKISTAN - SRILANKA
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
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
Earth Science Reviews 2001
Quaternary Science Reviews 2012
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
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
Mischke et al, 2013 (in press)
Intra Lake Variability In radiocarbon Reservoir ages And Its variability with time
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
Sucking In
Smearing out
Tie Point ↔ 5-10ka
Time Lines
Loess-Paleosol sequences
Kukla, 1986
Xifeng, China Magnetic Susceptibility
tuned to oceanic record
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
Vandenberghe et al., 1997 U ratio – 44-16µm/16-5µm
Grain Size records also seen to be covariant
Porter and An. Science
Deduction of Milankovitch periodicities based on Ages assignments using inferred ages for the loess/paleosol layers
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
Grain Size
Carbonate content 0.8m 5-10 ka Vandenberghe, 2012
EPISODIC ACCUMULATION & LONG HIATUSES
EPISODIC ACCUMULATION & LONG HIATUSES
Stevens – INQUA 2011 How does one compare these with Ocean and Ice cores with constant accumulation rates ?
S0 Loess-Soil
S1 Soil-Loess
Drier- Wetter
So
S1 In Xian Soil till 75ka
Soil
Soil
Soil
Singhvi et al. Earth Sci Revs
Ashok Singhvi DESERTS
Limits of Active dunes at LGM, Holocene and Present
Sarnthein ,1982 Synchronous expansion and contraction
ALBEDO CHANGES IN THE PASTPAST
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
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
Limits of Active dunes at LGM, Holocene and Present
Sarnthein ,1982
Synchronous expansion and contraction
Not tenable – needs a change
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
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)
From RC-2735 box cores
Composite
Temperature variationG. Bulloides
From RC-2730 box cores
Anderson et al., 2002
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
Kocurek, 1999
Creation of a terrestrial sedimentary record in non-trivial
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.
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
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
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.
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…”