Paleoecology of Bivalves from Lower Miocene of Kutch, India

Shibajyoti Das5th Year BS-MS

DES, IISER Kolkata

Outline• Introduction

• Previous work• Theme• Bivalve• Miocene global climatic scenario• Kutch

• Objectives• Material Methods• Results

• Taxonomic diversity• Rarefaction• γ diversity

• Morphological diversity• Discussion and Conclusion• References• Acknowledgement

http://www.fossilmall.com/Pangaea/pfossils/pf115/pfo433bb.JPG

Previous work• Physical triggers affect the biodiversity of organisms.

• Climate change – major driving force (Matthew, 1915).

• Increase in temperature – Increase in biodiversity (Mayhew et al. 2012).

• Evolutionary trend of Cenozoic Mollusc as a result of climatic shifts –

• North American (Roy et al., 2001)

• Antarctic (Ivany et al., 2000, 2003, 2004, 2008)

• European assemblages (Lockwood, 2005 )

• Decrease in Bivalve body size with an increase in temperature (Belanger, 2012).

Theme

• Possible effect of the physical trigger (climatic fluctuation) on

• Bivalve diversity and community structure

• Bivalve morphology (body size) from the Miocene of Kutch

Bivalves

• Good fossilization potential

• Common in the fossil record

• Accretionary growth recording events happening

during life

• δ18O and δ13C isotopic signature preserved

• Accretion: Adding discrete growth layers to

skeletons as they get larger.

http://paleoecology.syr.edu/research-pages/growth.html

Geologic time scale

Khari Nadi formation

Chhasra formation

Stratigraphy of Kutch after Biswas (1992)

Climatic fluctuations over the Tertiary Period

• Through the Tertiary climate varied from colder to warmer in

regular cycles.

• Average global temperature was warmer during the Tertiary

Period so that continental glaciations did not take place.

• Geochemical data demonstrate that the Miocene represents a

time of rapid palaeoclimatic change (Zachos et al. 2001).

Fluctuations during Miocene

Sea level estimates derived from New Jersey (Miller et al., 2005; Kominz et al., 2008) that provide a testable record of global sea-level. Also shown is the oxygen isotopic synthesis of Cramer et al. (2009).  NHIS = northern hemisphere ice sheets.  

Kutch, India

• The Early Miocene succession of Kutch represents a mixed carbonate-siliciclastic

depositional system (Kumar et al., 2009).

• The carbonate succession had abundant shallow marine benthic fauna consisting of shelled

organisms in large concentration.

• The carbonate-siliciclastic depoitional environment helps in good preservation of the

mollusc shell because:

• Carbonate shell

• Contrasting depositional environment

• Difference in texture of fossil and surrounding rocks

Objectives

• Characterization of Bivalves from Early Miocene of Kutch.

• Characterizing the nature of taxonomic and morphological diversity and

community structure of the bivalve community.

• Evaluating the possible effect of climatic change on the bivalve community.

Field area

Bio-assemblage

Field protocol• Selection of locality (ridge or river bed section).

• Identification of lithological units.

• Making brief lithologs.

• Collection of bulk lithological samples and fossils.

Methods used

Methods used

Identification protocol

• Paleodb database•Treaties of Invertebrate Paleontology•Borkar et al. 2004

Bivalve TaxonomyOstreidae

Veneridae

TellinidaePectinidae

GlycymeridaeCardiidae

Plicatulidae

Results

• Total Specimen Identified: 1479

• Khari Nadi formation : 902

• Chhasra formation: 577

• Number of identified Families:9

Family Khari Nadi Chassra

Arcidae 9 6

Cardiidae 38 6

Glycymeridae 10 2

Lucinidae 8 2

Plicatulidae 0 5

Pectenidae 234 50

Ostreidae 439 482

Tellinidae 56 8

Veneroidae 108 16

902 577

1. Taxonomic diversity

Abundance distribution

Family Khari Nadi (%) Chassra (%)Ostreidae 48.6 83.5Pectinidae 25.9 8.6Veneridae 11.9 2.7Tellinidae 6.2 1.3Arcidae 0.9 1.0Glycymeridae 1.1 0.3Lucininidae 0.8 0.3Cardiidae 4.2 1.0Plicatulidae 0 0.8

Rarefaction

• This curve is a plot of the number of taxa as a

function of the number of samples.

• Estimates the number of taxa that would have

been found if a smaller number of individuals

had been sampled.

A

B

Number of Individuals

Num

ber o

f Tax

a

γ diversity• Total taxonomic diversity in a landscape (Formation).

Mann-Whitney Test: p<<0.05

Most abundant families• Ostreidae

• Pectinidae

• Veneridae

• Tellinidae

Abundance in each locality

Khari nadiDominance = 0.47

ChassraDominance = 0.8

p = 0.0018

Results

• Body size measurement

• Length

• Height

• Total specimen measured: 373

• Khari Nadi formation : 281

• Chhasra formation: 92

• Number of Families whose specimens were measured: 4

Family Khari Nadi Chassra

Pectenidae 54 18

Ostreidae 125 65

Veneridae 69 6

Tellinidae 33 3

281 92

2. Morphological diversity

Body-Size plots

Percentage decrease: 49.35p << 0.05

Percentage decrease: 73.17p << 0.05

Percentage decrease: 30.63p << 0.05

Comparison of percentage shrink

Paleoclimate• δ18O values for two cross sectional

samples of Ostrea angulata

• Paleotemperature reconstruction from the δ18O values.

Khari Nadi

Chhasra

Khari Nadi

Chhasra

Khari Nadi

Discussion and Conclusion

• A significant increase in temperature from the older to the younger formation.

• Difference in abundance of families between the two formations.

• Significant difference in the γ diversity in the two formations.

Climate change and biodiversity• Beyond small geographical scales, biodiversity consistently decreases with latitude (Willig et

al. 2003; Hillebrand, 2004; Krug et al., 2009).

• Strong causal association between warmer climates and standing richness in marine realms (Rombouts, 2009; Tittensor et al., 2010).

• Increase in temperature – Increase in biodiversity (Mayhew et al. 2012).

Temperature Diversity

Discussion and Conclusion

• A significant change in the body size with body shrinkage in the

younger formation.

• Shrinkage percentage varies within families.

• Highest for epifaunal mobile (free swimmers)

• Low for epifaunal stationary (bysally attached)

• Lowest for infaunal

Temperature and body size

Figure: Working hypothesis of the major processes of climate change effects on organism size.

(1) Increased metabolic rate is likely to reduce body size unless organisms can consume enough additional resources to meet their increased demands.

(2) Decreased amounts of dissolved oxygen in warmer waters will make it difficult to meet increased metabolic needs.

(Sheridan and Bickford, 2001, Nature climate)

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compilation. Paleoceanography, 24(4).• Hillebrand H (2004) On the generality of the latitudinal diversity gradient. Am Nat 163:192–211.• Ivany, L. C., K. C. Lohmann, and W. P. Patterson, 2003, From Greenhouse to Ice-house: The Marine Eocene-Oligocene Transition, pp. 232–251, Columbia Univ. Press, New York • Ivany, L. C., W. P. Patterson, and K. C. Lohmann, 2000, Nature, 407: 887–890 • Ivany, L.C., Lohmann, K.C, Blake, D.B., 2008, GSA Bulletin, 120: 659-678. • Ivany, Linda C., Wilkinson, Bruce W., Lohmann, Kyger C, 2004, J. Sed.Res., 74: 7-19. • Kominz, M. A., Browning, J. V., Miller, K. G., Sugarman, P. J., Mizintseva, S., & Scotese, C. R. (2008). Late Cretaceous to Miocene sea‐level estimates from the New Jersey and Delaware

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Acknowledgements• Dr. Devapriya Chattopadhyay

• Saurav Dutta, Debarati Chattopadhyay, Mansi Jain, Mrinmoy Pal, Rohini Das, Neeti Mandal, Ravi Kiran, Debanjan Chandra, Jayjit Das and Dipanjana Dalui.

• Paleo lab members

• All members of the Department of Earth Sciences, IISER Kolkata

• Friends and family

Thank you