Re-evaluating modern and Palaeogene GDGT distributions; implications for SST reconstructions

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doi: 10.1016/j.gloplacha.2013.06.011
Author(s): Taylor, Kyle W. R.; Huber, Matthew; Hollis, Christopher J.; Hernandez-Sanchez, Maria T.; Pancost, Richard D.
Author Affiliation(s): Primary:
University of Bristol, Organic Geochemistry Unit, Bristol, United Kingdom
Purdue University, United States
GNS Science, New Zealand
Volume Title: Global and Planetary Change
Source: Global and Planetary Change, Vol.108, p.158-174. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181
Note: In English. Includes appendix. 170 refs.; illus., incl. 1 table
Summary: In this paper, we review the TEX86 palaeothermometer for sea surface temperature (SST) and evaluate its application to the Palaeogene, with a focus on the principal ecological, physical or chemical processes that can bias glycerol dialkyl glycerol tetraether (GDGT) distributions. Recent investigations of Palaeogene sediments have revealed temperature offsets between two different GDGT-based approaches, TEX86L and TEX86H, with the former agreeing with SST estimates derived from inorganic proxies (Hollis et al., 2012). These are surprising observations because the two GDGT approaches, although based on two distinct groups of compounds, apparently agree at SSTs>15°C in modern oceans. Here we reassess the relationship between raw GDGT distributions and the ratios used to construct TEX86H and TEX86 in both the modern core-top dataset and a new compilation of Palaeogene data. We show that the offset between TEX86H and TEX86L (ΔH-L) is a function of the GDGT-2/GDGT-3 ratio ([2]/[3] ratio), and that this can be used to separate low- and high-latitude GDGT distributions in the modern core-top dataset: a range of [2]/[3] ratios and ΔH-L values occur in polar regions, whereas [2]/[3] ratios are high and ΔH-L values are small at temperatures >15°C. However, in the Palaeogene dataset, we observe a wide range of [2]/[3] ratios, even for SST estimates above 15°C. Crucially, we find that water depth is a better discriminator of ΔH-L values and [2]/[3] ratios than SST in the combined modern and Palaeogene dataset: ΔH-L values are low (<3.0°C) and [2]/[3] ratios are high (>5.0) where water depth is >1000m. Modern water column studies show that the [2]/[3] ratios in suspended particulate matter (SPM) increase with depth, suggesting that high [2]/[3] ratios reflect a contribution from Archaea living in the deeper water column. This suggests that export dynamics influence GDGT-derived SST estimates. We argue for new approaches to SST reconstruction: 1) continued use of core-top calibrations, in which export dynamics have been implicitly incorporated into the current core-top calibration datasets, but with the influence of water depth taken into account; and 2) use of SPM or mesocosm-based calibrations, with water depth and palaeo-export dynamics independently assessed. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Calibration; Campbell Plateau; Caribbean Sea; Ceara Rise; Cenozoic; DSDP Site 277; DSDP Site 511; Deep Sea Drilling Project; East Pacific; Equatorial Atlantic; Equatorial Pacific; Ethers; Glycerol dialkyl glycerol tetraethers; IPOD; Leg 101; Leg 130; Leg 154; Leg 165; Leg 181; Leg 189; Leg 199; Leg 29; Leg 71; Little Bahama Bank; Modern analogs; North Atlantic; North Pacific; Northeast Pacific; Northwest Pacific; ODP Site 1121; ODP Site 1172; ODP Site 1218; ODP Site 628; ODP Site 803; ODP Site 925; ODP Site 929; ODP Site 998; Ocean Drilling Program; Ontong Java Plateau; Organic compounds; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleogene; Paleotemperature; Sea-surface temperature; Sedimentary rocks; South Atlantic; South Pacific; Southwest Pacific; Tasman Sea; Tertiary; West Pacific
Coordinates: S505353 S505353 E1765952 E1765952
S435800 S435700 E1495600 E1495500
N192923 N192923 W0825610 W0825610
N041215 N041216 W0432920 W0432922
Record ID: 2013077616
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands