Paleoceanographic processes and crises during the late Cretaceous and early Tertiary as recorded in basin, slope and platform series
Christian Scheibner, Jochen Kuss, Robert Speijer and John Reijmer (Kiel University)
DFG-Project Ku 642/19
- for the Paleogene this applies to the temperature maximum at the Paleocene-Eocene transition (Paleocene-Eocene thermal Maximum”, PETM), which is synchronous to the benthic extinction event (BEE) and as yet has mostly been identified in deep-marine basin sediments, but which can also be found in shallow-water sediments.
We study the effect of PETM on the biogenic composition of the platforms. In this context the correlation of biozonations between planktic foraminifera / calcareous nannoplankton and larger benthic foraminifera is of major importance.
Paleocene/Eocene Thermal Maximum (PETM): Tethyan Margin Records
Project by Christian Scheibner and Robert Speijer
The end of the Paleocene (~55 Ma) was marked by sudden global change, upsetting oceanic and atmospheric circulation and leading to the extinction of numerous deep-sea benthic foraminifera and a major turnover in land mammals. Biotic and geochemical anomalies observed world-wide relate to high latitude warming (subtropical conditions prevailed at Antarctica!) and a reversal in oceanic circulation: during a short period (<100 k.y.) dense warm and salty water, formed in low latitude basins (e.g. Tethyan margins), is thought to have filled the oceanic basins. This period is known as the Paleocene/Eocene Thermal Maximum, PETM (previously known as LPTM, and also as IETM). Just over a decade ago the abruptness of these events was first recognised. Today, this is regarded as one of the most significant periods of global change during the Cenozoic. Detailed study of these events could provide insight into geobiosphere dynamics in an extreme greenhouse world.
We studied the expression of the PETM along a depth transect across the tropical-subtropical Tethyan paleoshelf in Egypt. This approach enables the unravelling of biotic and environmental changes within different depth regimes and should lead to a better understanding of the controlling mechanisms.
Main results from Egypt:
Through detailed bio-, chemo- and ecostratigraphy we can accurately correlate the Egyptian to deep-sea records.
Benthic foraminiferal extinction was greatest in the deepest part of the basin (N), decreasing towards shallower depths (S). Short-term (10-100 k.y.) biotic perturbations, however, caused by sea-floor anoxia to dysoxia, can be monitored basin-wide up to middle neritic depths.
Benthic repopulation evolved through downslope expansion of several neritic communities, largely constituted by epi- and endobenthic taxa with opportunistic reproduction strategies.
Also ostracodes show a distinct turnover, but no major extinction event.
Simultaneously, unique planktic foraminifera communities, almost entirely composed of the surface dweller Acarinina, indicate anomalous surface conditions too.
The presence of the short-lived Morozovella allisonensis within this planktic assemblage indicates that some of the studied sections yield the best coverage of this interval discovered to date in exposed marine successions world-wide.
This event also marks a long-term (>1 m.y.) change to enhanced surface and sea-floor productivity, particularly in neritic domains and possibly relates to changes in oceanic and atmospheric circulation.
The epicontinental basin covering Egypt did not produce warm saline deep water during the late Paleocene.
The PETM is associated with regional and possibly eustatic sea-level changes.
Maastrichtian chalks overlain by Paleocene-Eocene marls and Eocene limestones in Wadi Nukhl, Sinai. This section belongs to the best documenting the PETM.
Preliminary studies on bathyal deposits on the northern Tethyan margin (Caucasus and Turkmenistan) indicate similar and simultaneous short-term biotic and paleoenvironmental changes. Further studies in upper Paleocene deep-sea, basinal, and basin-platform-transition successions are being undertaken in Egypt, Israel, Italy, Spain, and Tunisia.
The larger-foraminifera turnover (LFT) during the Paleocene–Eocene transition constitutes an important step in Paleogene larger-foraminifera evolution, involving a rapid increase in species diversity, shell size, and adult dimorphism. A platform-to-basin transect in Egypt provides new data on timing and causal mechanisms through correlation with planktic biozonations and through integration with regional paleoenvironmental data. The LFT, coinciding with the boundary between shallow benthic biozones SBZ4 and SBZ5, closely correlates with the Paleocene–Eocene Thermal Maximum (PETM). Enhanced oligotrophy from the late Paleocene onward favored the diversification of K-strategist larger foraminifera. We suggest that a short-term eutrophication during the PETM led to a temporary decline of extreme K-strategist larger-foraminifera species, providing opportunities for new taxa with different ecological strategies to develop. During post-PETM oligotrophic conditions, these new taxa were able to evolve rapidly and soon dominated early Eocene larger-foraminifera assemblages, whereas many Paleocene taxa gradually disappeared. The success of larger foraminifera during the early Paleogene appears climatically controlled. Because of the vulnerability of corals to high surface-water temperatures, the late Paleocene to early Eocene global warming may have favored larger foraminifera at the expense of corals as the main carbonate-producing component on carbonate platforms at lower latitudes.
Biostratigraphy and comparison of trends in evolution and distribution of larger foraminifera, d18O isotopes, coral reef abundance, and trophic resource continuum (TRC). Inset: events associated with the Paleocene/Eocene boundary; CIE = carbon isotopic excursion; BEE = benthic extinction event; LFT = larger foraminifera turnover.
Literature:
Özcan, E., Scheibner, C., Boukhalfa, K., (2014): Orthophragminids (foraminiferida) across the Paeleocene/Eocene transition from Galala, Egypt: Taxonomy and paleobiogeographic implications, Journal of Foraminiferal Research. 44: 203-229 PDF
Höntzsch, S., Scheibner, C., Brock, J.P., Kuss, J. (2013) Circum-Tethyan carbonate platform evolution during the Palaeogene: the Prebetic platform as test for climatically-controlled facies shifts, Turkish Journal of Geology 22: 891-918. PDF
Speijer, R.P., Scheibner, C., Stassen, P., Morsi, A.M.M. (2012): Response of marine ecosystems to deep time global warming: a synthesis of biotic patterns across the Paleocene-Eocene thermal maximum, Austrian Journal of Earth Sciences 105: 6-16 PDF
Boukhary, M., Scheibner, C. (2011): New Paleocene large cassiduline foraminifera (Cassidinidae fam.nov., Miscellanacea) from Egypt and its phylogeny. Historical Biology 23: 349-366
Höntzsch, S., Scheibner, C., Guasti, E., Kuss, H.J., Marzouk, A., Rasser, M.W. (2011) Increasing restriction of the Egyptian shelf during the Early Eocene? – New insights from a southern Tethyan carbonate platform. Palaegeography, Palaeoclimatology, Palaeoecology 302: 349-366. PDF
Höntzsch, S., Scheibner, C., Kuss, H.J., Marzouk, A.M., Rasser, M.W. (2011) Tectonically driven carbonate ramp evolution at the southern Tethyan shelf: the Lower Eocene succession of the Galala Mountains, Egypt. Facies 57: 51-72. PDF
Schulte, P., Scheibner, C., Speijer, R.P. (2011): Fluvial discharge and sea-level changes controlling black shale deposition during the Paleocene-Eocene Thermal Maximum in the Dababiya Quarry Section, Egypt. Chemical Geology 285: 167-183. PDF
Boukhary, M., Scheibner, C. (2009): On the Origin of Nummulites: Urnummulites schaubi n.gen. n.sp. from the Late Paleocene of Egypt. Micropalaeontology 55: 413-420. PDF
Hoentzsch, S., Scheibner, C., Marzouk, A.M., Rasser, M.W. and Kuss, H.J., (2009): Multiple Early Eocene thermal maxima at low latitude platform carbonates - The Eocene succession of the Galala Mountains, Egypt. In: E.M. Crouch, C.P. Strong and C.J. Hollis (Editors), Climatic and biotic events of the Paleogene (CBEP 2009), extended abstracts from an international conference in Wellington, New Zealand, 12-15 January 2009. GNS Science Miscellaneous Series 18, pp. 70-74.
Scheibner, C., Speijer R.P. (2009): Recalibration of shallow-bentic zonations across the Paleocene-Eocene boundary: Evidences from Egypt, Geologica Acta 7:195-214. PDF
Scheibner, C., Speijer, R.P. (2008): Decline of coral reefs during late Paleocene to early Eocene global warming. eEarth, 3: 19-26 PDF
Scheibner, C., Speijer, R.P. (2008): Late Paleocene–early Eocene Tethyan carbonate platform evolution — A response to long- and short-term paleoclimatic change. Earth-Science Reviews, 90: 71-102. PDF
Scheibner, C., Rasser, M., Mutti, M. (2007): The Campo section (Pyrenees, Spain) revisited: Implications for changing benthic carbonate assemblages across the Paleocene-Eocene boundary, Palaeogeography, Palaeoclimatology, Palaeoecology, 248: 145-168. PDF
Rasser, M.W, Scheibner, C., Mutti, M. (2005): A paleoenvironmental standard section for Lower Ilerdian tropical carbonate factories (Pyrenees, Spain; Corbieres, France), Facies 51, 217-232. PDF
Scheibner, C. Speijer, R. P., Marzouk, A. M. (2005): Larger foraminiferal turnover during the Paleocene/Eocene thermal maximum and paleoclimatic control on the evolution of platform ecosystems, Geology 33: 493-496. PDF