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| Titel |
Carbon isotope stratigraphy and palynology of an eastern Tethyan Cretaceous-Paleogene boundary section from Sumbar, Turkmenistan |
| VerfasserIn |
I. Gilmour, C. A. Pearce, D. Jolley, M. A. Sephton, M. Widdowson, M. A. Gilmour |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068882
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| Zusammenfassung |
| A number of marine sequences across the K/Pg boundary have been identified that offer reasonably continuous records and relatively high sedimentation rates, most notably those near Tethyan continental margins. However, few Eastern Tethys K/Pg localities have been studied compared to the well-known North African and Southern European sites. Here we present a high-resolution stable carbon isotope and palynological record of a 2m thick section across the K/Pg boundary from the eastern Tethys at Sumbar in Turkmenistan (38°28’N, 56°14’E). The stratigraphy and inorganic geochemistry of the section used in this study, SM-4, has been described in detail by [1].
A moderately diverse series of palynofloras were recovered from the samples spanning the K/Pg boundary with a late Maastrichtian assemblage comparable to that described from Tunisia [2]. Above the K/Pg boundary a dinocyst assemblage dominated by Areoligera is observed, reinforcing the similarity with Tunisia, that we interpret as representing a marine transgression by eutrophic water masses with the levels of Areoligera decreasing up section with a decline in nutrient availability.
Carbon isotope stratigraphy of bulk carbonate and bulk organic matter reveal correlated negative carbon isotope excursions (CIEs) across the K/Pg boundary. The extent of the CIE and the concomitant drop in carbonate content parallels that observed for bulk and fine fraction carbonate isotopic analyses from other K/Pg sections. The negative CIE of bulk organic matter is similar in magnitude to CIEs for organic matter that have been observed at only a few other marine K/Pg sections. In contrast, the marked CIE observed in bulk organic matter is not evident in the carbon isotopic compositions of algal lipids. We interpret this as a geochemical signature of post-K/Pg algal blooms.
Recent analysis identified the K/Pg boundary in the Boltysh meteorite crater sediment fill and reported evidence of a marine incursion into the crater during the Tethyan post K-Pg marine transgression [3]. This marine incursion is >1m above the K/Pg boundary and is marked by the same species of Areoligera recorded at Sumbar. Consequently, the potential for the existence of either a highly condensed section or a disconformity within at least some Tethyan K/Pg marine sections must be considered.
[1] Alekseev, A.S. et al., (1988 ) Int. Geol. Rev. 30, 121–135; [2] Slimani, H., Louwye, S., Toufiq, A. (2010) Palynology 34, 90–124; [3] Jolley, D.W., Gilmour, I., Gurov, E., Kelley, S., Watson, J. (2010) Geology 38, 835–838. |
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