Eocene-Oligocene planktonic foraminifera of ODP Hole 135-841B

A middle Eocene to lower Oligocene sedimentary sequence was drilled at Site 841 in the Tonga forearc region during Ocean Drilling Program Leg 135. A 56-m-thick sequence of volcanic sandstone, spanning from Cores 135-841B-4IR to -47R (549.1 to 605 mbsf), unconformably overlies rhyolitic volcanic basement. The middle Eocene planktonic foraminifer assemblages (P Zone?), which occur in association with larger benthic foraminifers, include spinose species of Acarinina, Morozovella, and Truncorotaloides, but their abundance is low. Late Eocene and early Oligocene faunas are abundant and show the highest diversity of the Paleogene sequence drilled at this site. They have been assigned to Zones P15-16 and P18, respectively. The Eocene/Oligocene boundary was not recognized because of a hiatus in which Zone P17 (37.2-36.6 Ma) was missing. Another hiatus is recorded in the interval between the middle and late Eocene, spanning at least 1.8 Ma. Paleogene assemblages of Site 841 contain equal numbers of warm- and cool-water species, an attribute of the warm middle-latitude Paleogene fauna of the Atlantic Ocean. In particular, common to high abundances of cool-water taxa, such as Globorotaloides, Catapsydrax, Tenuitella, and small globigerinids, may be related to the opening of a shallow seaway south of Tasmania permitting the influx of cool Indian Ocean waters into the South Pacific before the late Eocene (approximately 37 Ma).

Benthic foraminifera of cores from ODP Leg 117

The relative abundances of benthic foraminifers from the Oman margin have been analyzed from ODP Sites 725 and 726 near the upper boundary of the oxygen-minimum zone (OMZ) and 728 near the lower boundary. The relative abundance pattern of the benthic foraminiferal species in the two shallow sites show synchronous changes, which, together with variations in the faunal composition, may be attributed to changes in the location of the upper boundary of the OMZ during the last 7 million years. At the deeper site, the relative abundance pattern shows considerable variation in the faunal composition during the last 8 million years. The strong dominance of the shallow-water species Ammonia beccarii during the early Pliocene at Site 728 suggests a water depth less than 400 m during the early Pliocene and subsequent subsidence during the middle and late Pliocene to the present > 1400 m water depth.

Distribution of ostracoda in the lower Cretaceous succession of ODP Hole 80-549 (Figure 3)

Site 549 recovered a Lower Cretaceous succession which has been shown to include parts of the Barremian and Albian stages. Forty-four species of Ostracoda are illustrated and their stratigraphic distribution used to recognise three major facies units. An high diversity inner shelf facies earlier in the Barremian gives way to a low diversity, outer shelf facies, higher in the succession. The early Albian appears to indicate a return to an inner shelf fauna. The faunas recovered have been compared to similar faunas elsewhere in N. W. Europe.

Sedimentological and benthic foraminiferal data pertaining to ODP Holes 208-1262A and 208-1263C

Eocene Thermal Maximum 2 (ETM2) occurred ~1.8 Myr after the Paleocene Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion coupled with warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak ETM2. The sites are in close proximity, so differences in surface productivity cannot have caused this differential effect. Instead, on the basis of an analysis of climate modelling experiments, we infer that changes in ocean circulation pattern across ETM2 may have resulted in more pronounced warming at intermediate depths (Site 1263). The effects of more pronounced warming include increased metabolic rates, leading to a decrease in effective food supply and increased deoxygenation, thus potentially explaining the more severe benthic impacts at Site 1263. In response to more severe benthic disturbance, bioturbation may have decreased at Site 1263 as compared to Site 1262, hence differentially affecting the bulk carbonate record. We use a sediment-enabled Earth system model to test whether a reduction in bioturbation and/or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk d13C and sharper transition in wt% CaCO3 at Site 1263. We find that both enhanced acidification and reduced bioturbation during peak ELMO conditions are needed to account for the observed features. Our combined ecological and modelling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary, but drastic, loss of benthic biodiversity and abundance.

Distribution, genesis and age of the Schlagwasser breccia (Warstein anticline, Rhenish massif)

The name "Schlagwasser breccia" is a synopsis of several debris flows in the Warstein area, which can be derived from the Warstein carbonate platform and the Scharfenberg reef. Though only locally developed, the breccia is important for the understanding of paleogeography and sedimentology in the Eastern Sauerland. Considering this breccia some gravitational-resedimentary slide movements between a high, consisting of reef carbonates, and a basin with flinz beds can be pointed out. From the uppermost Middle Devonian to the lowermost Lower Carboniferous several slides yielded the sedimentary components building up the 30 to 50 m thick polymict breccia. Some breccias were redeposited repeatedly as can be verified by different conodont maxima in single samples. Supplying area was the western part of the Warstein high, from which the slide masses glided off to the East and Southeast, more seldom to the West and Westsouthwest. All conodont zones from the upper Middle Devonian up to the lowermost Carboniferous could be identified in the Schlagwasser breccia. Therefore, an uninterrupted continuous sedimentation must have been prevalent in the supplying area; today this area nearly is denuded of flinz beds and cephalopod limestones. The slide masses spread transgressively to the East up to a substratum consisting of different units as massive limestone, flinz beds and cephalopod limestone; they are overlapped by Hangenberg beds, alum schists and siliceous rocks of the Lower Carboniferous. Parts of the substratum were transported during the progress of the slide masses. Proximal and distal parts of the flow masses can be distinguished by the diameter of the pebbles. Graded bedding and banking structures are marked only rarely. Way of transport was up to 3 km. Differently aged slide masses do not always overlap, but are placed side by side, too. Usually the slide masses do not spread out upon a greater area during sedimentation, but form closely limited debris flows. Synsedimentary fracturing and tilting of the reef platform, epirogenetic movements and seaquakes caused the slides. The entire formation period of the breccia includes about 20 millions of years. The longevity of the events points to solid paleomorphological situations around the eastern margin of the carbonate platform.