The fidelity of oxygen and strontium isotope values from shallow shelf settings: Implications for temperature and age reconstructions

Jocelyn A. Sessa, Linda C Ivany, Trevor H. Schlossnagle, Scott Douglas Samson, Stephen A. Schellenberg

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age, respectively. While open ocean samples are the standard source for these measures, shelf settings can also provide detailed records. However, the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions (such as freshwater influx) confound regional and global signals. Here, we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment. Data are derived from mollusc shells collected from a stratigraphically restricted, transgressive unit in the early Eocene (~55Ma) of the US Gulf Coastal Plain (GCP). Lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region, whereas more typically marine facies predominated elsewhere. Isotopic composition varies predictably with paleoenvironmental setting; shells from the estuary have δ 18O values and 87Sr/ 86Sr ratios that reflect high freshwater input. Specimens in the eastern GCP, however, from within and between outcrops separated by up to 400km, all yield similar results. Serial microsampling reveals congruence not only in mean δ 18O values, but also in winter and summer extremes. Estimated paleotemperatures (mean annual temperature of 26°C) agree well with proxy and model evidence for the early Eocene and the GCP, and 87Sr/ 86Sr ratios are consistent with the established early Eocene seawater ratio. The fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry.

Original languageEnglish (US)
Pages (from-to)27-39
Number of pages13
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume342-343
DOIs
StatePublished - Jul 15 2012

Fingerprint

strontium
strontium isotope
coastal plains
coastal plain
oxygen isotope
isotopes
Eocene
shell (molluscs)
paleotemperature
oxygen
carbonates
isotopic composition
estuaries
oceans
estuary
shell
carbonate
temperature
freshwater input
fossil assemblage

Keywords

  • Age reconstruction
  • Mollusc
  • Palaeoclimatology
  • Sclerochronology
  • Shelf
  • Stable isotopes

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Palaeontology
  • Earth-Surface Processes
  • Oceanography

Cite this

The fidelity of oxygen and strontium isotope values from shallow shelf settings : Implications for temperature and age reconstructions. / Sessa, Jocelyn A.; Ivany, Linda C; Schlossnagle, Trevor H.; Samson, Scott Douglas; Schellenberg, Stephen A.

In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 342-343, 15.07.2012, p. 27-39.

Research output: Contribution to journalArticle

@article{740cc69655424f3d9ae0c653e153b84a,
title = "The fidelity of oxygen and strontium isotope values from shallow shelf settings: Implications for temperature and age reconstructions",
abstract = "The oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age, respectively. While open ocean samples are the standard source for these measures, shelf settings can also provide detailed records. However, the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions (such as freshwater influx) confound regional and global signals. Here, we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment. Data are derived from mollusc shells collected from a stratigraphically restricted, transgressive unit in the early Eocene (~55Ma) of the US Gulf Coastal Plain (GCP). Lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region, whereas more typically marine facies predominated elsewhere. Isotopic composition varies predictably with paleoenvironmental setting; shells from the estuary have δ 18O values and 87Sr/ 86Sr ratios that reflect high freshwater input. Specimens in the eastern GCP, however, from within and between outcrops separated by up to 400km, all yield similar results. Serial microsampling reveals congruence not only in mean δ 18O values, but also in winter and summer extremes. Estimated paleotemperatures (mean annual temperature of 26°C) agree well with proxy and model evidence for the early Eocene and the GCP, and 87Sr/ 86Sr ratios are consistent with the established early Eocene seawater ratio. The fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry.",
keywords = "Age reconstruction, Mollusc, Palaeoclimatology, Sclerochronology, Shelf, Stable isotopes",
author = "Sessa, {Jocelyn A.} and Ivany, {Linda C} and Schlossnagle, {Trevor H.} and Samson, {Scott Douglas} and Schellenberg, {Stephen A.}",
year = "2012",
month = "7",
day = "15",
doi = "10.1016/j.palaeo.2012.04.021",
language = "English (US)",
volume = "342-343",
pages = "27--39",
journal = "Palaeogeography, Palaeoclimatology, Palaeoecology",
issn = "0031-0182",
publisher = "Elsevier",

}

TY - JOUR

T1 - The fidelity of oxygen and strontium isotope values from shallow shelf settings

T2 - Implications for temperature and age reconstructions

AU - Sessa, Jocelyn A.

AU - Ivany, Linda C

AU - Schlossnagle, Trevor H.

AU - Samson, Scott Douglas

AU - Schellenberg, Stephen A.

PY - 2012/7/15

Y1 - 2012/7/15

N2 - The oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age, respectively. While open ocean samples are the standard source for these measures, shelf settings can also provide detailed records. However, the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions (such as freshwater influx) confound regional and global signals. Here, we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment. Data are derived from mollusc shells collected from a stratigraphically restricted, transgressive unit in the early Eocene (~55Ma) of the US Gulf Coastal Plain (GCP). Lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region, whereas more typically marine facies predominated elsewhere. Isotopic composition varies predictably with paleoenvironmental setting; shells from the estuary have δ 18O values and 87Sr/ 86Sr ratios that reflect high freshwater input. Specimens in the eastern GCP, however, from within and between outcrops separated by up to 400km, all yield similar results. Serial microsampling reveals congruence not only in mean δ 18O values, but also in winter and summer extremes. Estimated paleotemperatures (mean annual temperature of 26°C) agree well with proxy and model evidence for the early Eocene and the GCP, and 87Sr/ 86Sr ratios are consistent with the established early Eocene seawater ratio. The fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry.

AB - The oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age, respectively. While open ocean samples are the standard source for these measures, shelf settings can also provide detailed records. However, the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions (such as freshwater influx) confound regional and global signals. Here, we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment. Data are derived from mollusc shells collected from a stratigraphically restricted, transgressive unit in the early Eocene (~55Ma) of the US Gulf Coastal Plain (GCP). Lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region, whereas more typically marine facies predominated elsewhere. Isotopic composition varies predictably with paleoenvironmental setting; shells from the estuary have δ 18O values and 87Sr/ 86Sr ratios that reflect high freshwater input. Specimens in the eastern GCP, however, from within and between outcrops separated by up to 400km, all yield similar results. Serial microsampling reveals congruence not only in mean δ 18O values, but also in winter and summer extremes. Estimated paleotemperatures (mean annual temperature of 26°C) agree well with proxy and model evidence for the early Eocene and the GCP, and 87Sr/ 86Sr ratios are consistent with the established early Eocene seawater ratio. The fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry.

KW - Age reconstruction

KW - Mollusc

KW - Palaeoclimatology

KW - Sclerochronology

KW - Shelf

KW - Stable isotopes

UR - http://www.scopus.com/inward/record.url?scp=84862527980&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84862527980&partnerID=8YFLogxK

U2 - 10.1016/j.palaeo.2012.04.021

DO - 10.1016/j.palaeo.2012.04.021

M3 - Article

AN - SCOPUS:84862527980

VL - 342-343

SP - 27

EP - 39

JO - Palaeogeography, Palaeoclimatology, Palaeoecology

JF - Palaeogeography, Palaeoclimatology, Palaeoecology

SN - 0031-0182

ER -