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 language | English (US) |
|---|---|
| Pages (from-to) | 27-39 |
| Number of pages | 13 |
| Journal | Palaeogeography, Palaeoclimatology, Palaeoecology |
| Volume | 342-343 |
| DOIs | |
| State | Published - Jul 15 2012 |
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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 journal › Article
}
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 -