Alfonso Pardo

Paleoenvironmental changes across the Cretaceous–Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy

Abstract The Koshak section of the Mangyshlack Peninsula, Kazakhstan, is one of the most complete Cretaceous–Tertiary (K–T) transitions known from the boreal Paratethys. Cretaceous species richness is low (11 to 13 species), except for a peak of 20 species near the K/T boundary in the uppermost Maastrichtian (top 50 cm) that represents the temporary incursion of low-latitude taxa. This maximum species richness occurred during climatic warming associated with increased humidity, as suggested by clay mineral analyses. Biofacies analysis suggests external platform conditions at this time, followed by a more humid climate, a sea-level transgression, and deepening basinal facies in the lower Danian Subzone P1a. Shallower platform conditions resumed in Danian Subzones P1b and P1c, accompanied by a cooler and probably more arid climate. No abrupt mass extinction occurred at the Koshak K/T boundary which is marked by an Ir anomaly, a clay layer and the first appearance of Tertiary planktic foraminifera. The influx of lower-latitude species ends at or before the K/T boundary, whereas the majority of the indigenous Cretaceous assemblage survived into the Danian. These data suggest that long-term climatic changes may have been the principal factors in the progressive demise of the Cretaceous planktic foraminifera in the eastern boreal Paratethys.

Planktic foraminiferal turnover across the Paleocene-Eocene transition at DSDP Site 401, Bay of Biscay, North Atlantic

Abstract Planktic foraminifera across the Paleocene-Eocene transition at DSDP Site 401 indicate that the benthic foraminiferal mass extinction occurred within Subzone P 6a of Berggren and Miller (1988), or P5 of Berggren et al. (1995) and coincident with a sudden 2.0%. excursion in δ13C values. The benthic foraminiferal extinction event (BFEE) and δ13C excursion was accompanied by a planktic foraminiferal turnover marked by an influx of warm water species (Morozovella and Acarinina), a decrease in cooler water species (Subbotina), a sudden short-term increase in low oxygen tolerant taxa (Chiloguembelina), and no significant species extinctions. These faunal changes suggest climatic warming, expansion of the oxygen minimum zone, and a well stratified ocean water column. Oxygen isotope data of the surface dweller M. subbotina suggest climate warming beginning with a gradual 0.5%. decrease in δ18O in the 175 cm preceding the benthic foraminiferal extinction event followed by a sudden decrease of 1%. (4 °C) at the BFEE. The δ13C excursion occurred over 27 cm of sediment and, assuming constant sediment accumulation rates, represents a maximum of 23 ka. Recovery to pre-excursion gd13C values occurs within 172 cm, or about 144 ka. Climate cooling begins in Subzone P 6c as indicated by an increase in cooler water subbotinids and acarininids with rounded chambers and a decrease in warm water morozovellids.

Climatic evolution on the southeastern margin of the Tethys (Negev, Israel) from the Palaeocene to the early Eocene: focus on the late Palaeocene thermal maximum

During the early Palaeocene (zones P1 to P2), the southeastern Tethyan margin experienced a warm and humid climate with high rainfall as indicated by the abundance of kaolinite within marine sedimentary rocks. Subsequently, in Zone P2, arid climatic conditions evolved in the coastal basins of the southern Tethys margin as indicated by the gradual disappearance of kaolinite and the increased abundance of palygorskite and sepiolite. Arid climatic conditions persisted during the Selandian and Thanetian (late Palaeocene) and reached a maximum in the Ypresian (early Eocene). During the late Palaeocene thermal maximum, warm climatic conditions were associated with increased aridity and led to sea surface warming, though not bottom water warming, as suggested by the planktic δ18O excursion observed at the Zomet Telalim basin (Negev, Israel). Strongly reduced surface productivity accompanied by unusually light δ13C are associated with the late Palaeocene thermal maximum in the Negev as well as globally.

Stability and change in Tethyan planktic foraminifera across the Paleocene–Eocene transition

Abstract Examination of planktic foraminifera in the Tethys basin during the Paleocene–Eocene transition reveals two stasis intervals that are separated by a major saltation event coincident with the P–E short-term perturbation in global climate and oceanography. Changes occurred at many spatial and temporal scales as well as many taxonomic and ecologic hierarchical levels, though with various rates and magnitudes. The stasis intervals are marked by slow changes at the species level and account for 50% of the observed first and last appearances during a 2.5 Myr interval. The saltation event is marked by rapid changes at the species and morpho-guild levels and accounts for the remaining 50% of first and last appearances during an interval of about 100–200 kyr. Despite these changes, many taxonomic and ecologic units, such as the depth assemblages and genera, and faunal parameters, such as species richness and turnover rates, are stable with respect to the P–E perturbation. This coexistence of change and stability marks the crisis of Tethyan planktic foraminifera across the P–E transition and reveals the possible dynamics of ecological evolution.

Climatic evolution on the southern and northern margins of the Tethys from the Paleocene to the early Eocene

The late Paleocene corresponds to one of the more prominent climatic changes in Earth history with a warming of 6 to 8°C in deepand high-latitude surface waters (referred as late Paleocene thermal maximum, or LPTM; Kennett & Stott 1991). During the LPTM the abundance of kaolinite in oceanic sediments indicates a time of high humidity with enhanced chemical weathering in the South Atlantic and southern Ocean (Antarctica) (Robert & Chamley 1991). This period of warming and high rainfall has also been observed in lower latitude sections (central North Sea: Knox 1996; New Jersey continental margin: Gibson et al. 1993; Basque Basin, northern Spain: Gawenda et al. 1999). In the coastal basins and peri-marine environments of West Africa, from Morocco to Benin, palygorskite deposition increased during the late Paleocene and dominated the clay fraction in the early Eocene. This important palygorskite episode indicates that low latitudes, and especially their coastal areas, were submitted to intensive dryness and evaporation (Robert & Chamley 1991). Based mainly on the clay mineral variations and the carbon and oxygen isotopic records observed in some sections located in the Tethys (Tunisia, Israel, Egypt, Spain, Kazakstan, Uzbekistan), we attempt, in this study to reconstruct the climate evolution on the southern and northern Tethyan margins from the Paleocene to the Eocene, with special attention to the LPTM. During the early Paleocene, southern Tunisia, located close to the Saharan platform, and the Negev area (Israel) are characterized by the abundance of kaolinite indicating humidity and warmth during this period. The simultaneous gradual disappearance of kaolinite to the benefit of palygorskite and sepiolite in these two regions located at about the same latitude (c. 20°N), but separated by more than 2,700 km suggests a latitudinal change from a humid and warm climate to an arid one. In southern Tunisia the development of arid conditions coincides with the first occurrence of phosphate deposits. On the Arabian Platform these arid climatic conditions were already initiated in the Danian (base of planktic Zone P2) and settled largely in the Selandian (middle of Zone P3). This aridity persisted through the late Paleocene, reaching a maximum in the early Eocene coinciding with those observed in West Africa (Benin to Morocco). During this time interval, gypsum deposits were accumulated over vast areas of the Arabian Peninsula (Oberhansli 1992) as a result of enhanced evaporation. In Egypt, during this period the increase of kaolinite in direction to the shoreline to the south could reflect increased humidity toward the continental hinterland in contrast with the arid climatic conditions developed in the peri-marine environments at the same time. During the LPTM, northern Tunisia and southern Spain are characterized by a sharp but short-lived increase in kaolinite relative to smectite and mica which can be related to the humid episode affecting mainly high latitude areas and the North Atlantic. The abrupt decrease in kaolinite above the LPTM to the benefit of smectite in northern Tunisia and of palygorskite in southern Spain, indicates increased aridity in this part of the Tethys