Search

We present an integrated, high-resolution, biostratigraphical, mineralogical, and geochemical characterization of the well-exposed Upper Paleocene -Lower Eocene stratigraphic succession of the Surghar Range (Baroch Nala section, NE Pakistan). The faunal assemblages from the Baroch Nala section, dominated by hyaline benthic foraminifera and green calcareous algae, along with the significant terrigenous fraction and the presence of terrestrially derived organic matter, testify to the deposition in a low-energy shallow-marine environment. Such environmental conditions, coupled with weak diagenetic effects, allow us to integrate a continuous record of carbon stable isotopes with a detailed account of the biotic response by carbonate-producing assemblages, paleoclimatic information based on clay-minerals, and information on volcanic activity based on mercury concentrations. The environmental evolution from the Late Paleocene up to the Paleocene Eocene Thermal Maximum (PETM) is clearly documented, including the weaker warm excursion that precedes the PETM (i.e. the Pre-Onset Excursion “POE”), and the evolution of large benthic foraminiferal assemblages. The overall record perfectly shows how the turnover in benthic carbonate producers started with the onset of the PETM and was completed by the time the excursion ended, highlighting how (geologically) brief environmental oscillations can have long lasting effects on the biosphere.

This paper analyses the lower to middle Eocene carbonate succession exposed at the Island of Pag (Croatia), in the External Dinarides, providing its palaeoenvironmental, palaeobathymetric, and stratigraphic reconstruction. A total of 125 samples have been collected within the Foraminiferal Limestone and the overlying Transitional Beds units cropping out in the sites of Vr & ccaron;i & cacute;i and Pag for the quantitative analysis of the skeletal assemblage (point counting) and the foraminiferal association (area counting), including both large benthic and small benthic foraminifera. Further samples were collected from the overlying Dalmatian Flysch, to constrain the age of the top of the succession using calcareous nannofossil biostratigraphy. On these bases, the Foraminiferal Limestone has been dated from the Ypresian to the middle Eocene (late Lutetian/early Bartonian). Thanks to the analysis of the skeletal and foraminiferal assemblages, and the use of multivariate statistics, seven main biofacies were identified within the Foraminiferal Limestone and one biofacies within the Transitional Beds. The porcelaneous and agglutinated benthic foraminifera biofacies (BF1) indicates a well-illuminated, oligotrophic to mesotrophic, shallow water, lagoonal environment. The hyaline SBF and encrusting benthic foraminifera biofacies (BF2) developed in a shallow water, inner-ramp environment, and is related to a vegetated seafloor. The nummulitid biofacies (BF3) indicates a moderately high energy, shallow water environment, whereas the comminuted bioclasts and nummulitid biofacies (BF4) corresponds to a low-energy, shallow water environment, and both deposited in inner-to-middle ramp settings. The nummulitid and orthophragminid biofacies (BF5) indicates a moderate energy environment, deposited in middle ramp settings. The nummulitid and serpulid biofacies (BF6) consists of transported material from the inner ramp deposited in middle ramp settings. The orthophragminid a

The previously scarce fossil record of Ziphiidae (beaked whales) has greatly increased recently thanks to the serendipitous discovery of high specimen concentrations along deep seafloors as well as to abundant inland finds from the Upper Miocene of the Pisco Formation (East Pisco Basin, Peru). In the latter unit, ziphiid remains are indeed among the most prevalent of the whole cetacean assemblage, being represented by four distinct genera and species plus at least two as-yet unnamed taxa. Here, we describe a fifth ziphiid genus and species from the Pisco strata, Mamaziphius reyesi n. gen. n. sp., based on a partial cranium from mid-Tortonian (lower Upper Miocene, 9.1-9.0 Ma) strata exposed at the locality of Cerros la Mama y la Hija. Though reminiscent of the extant genus Berardius, the holotype skull lacks two diagnostic characters of Berardiinae, namely, an isolated rounded protuberance formed by the interparietal or frontals on the posterior part of the vertex, and a posterior transverse narrowing of the nasals and frontals at the vertex. Our phylogenetic analysis reveals that Mamaziphius n. gen. is nested within the crown ziphiids, as sister group of the berardiines. In addition, we introduce two new clade names within Ziphiidae, namely, Messapicetiformes (for the so-called “Messapicetus clade”) and Vomeroziphii (for Ziphiinae + Hyperoodontinae and closely related forms). Another fragmentary specimen from the Pisco Formation is also briefly described herein. Furthermore, a comprehensive reappraisal of the geological age of the fossil beaked whales of Peru is provided based on new age calibrations, thus restricting the whole rich Peruvian record of this family (including the earliest-branching ziphiid, Ninoziphius platyrostris, which comes from Pisco-equivalent strata of the Sacaco area) to a Tortonian-Messinian interval younger than 9.10 Ma. No other inland unit worldwide preserves a record of fossil ziphiids as abundant, diverse and chronostratigraphically well

We investigate the Palaeocene succession of the Hazara Basin (Northern Pakistan) to better understand the impact of climate change on marine carbonate-producing organisms. These shallow-water carbonates, deposited during the Late Palaeocene, before the onset of the Palaeocene-Eocene Thermal Maximum, were studied using a quantitative approach to highlight changes in the skeletal assemblage. We recognise a decrease in the abundance of colonial corals and green calcareous algae and an increase in larger benthic foraminifera and red calcareous algae from the early Thanetian to the late Thanetian. Increasing temperatures may represent a plausible cause for the decline of the more sensitive colonial corals in favor of the more tolerant larger benthic foraminifera. A similar pattern is observed in most successions deposited along the margins of the Neotethys Ocean, suggesting a connection with the Late Palaeocene environmental changes that heralded the PETM hyperthermal event. Our stratigraphic analysis of the Hazara Basin strata suggests that the biotic turnovers occurred during the Palaeocene – Eocene transition started already before the onset of the Palaeocene Eocene Thermal Maximum as recorded by the geochemical proxies.

The bottom water conditions in the Central South Pacific (CSP) and associated changes in the Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW) under warmer-than-present conditions need to be better understood. These water masses transfer their properties to the major ocean basins. We analyzed Late Miocene to Early Pliocene (5.6–3.6 Ma) marine sediment core sections from the CSP for benthic foraminifera, ice rafted debris (IRD), Ostracoda, planktic foraminifera Orbulina universa abundance, and organic geochemical proxies to assess the bottom water characteristics under warmer-than-present day conditions. A significant increase in IRD abundance between 5.3 and 4.9 Ma marks the Early Pliocene warm phase. The benthic foraminiferal assemblages indicate shifts in bottom water conditions over time in the CSP region. Between 5.6 and 5.3 Ma, predominantly oxygenated bottom water with moderate organic matter flux prevailed. This shifted to suboxic conditions with increased organic matter flux from 5.3 to 4.9 Ma. Subsequently, between 4.9 and 4.4 Ma, bottom water conditions alternated frequently between oxic and suboxic states. Enhanced bottom water formation and inflow of LCDW and AABW in the CSP during 4.4–4.0 Ma promoted oxygenated conditions, accompanied by low organic export flux. However, sluggish bottom water circulation from 4.0 to 3.6 Ma reverted to suboxic conditions, associated with increased carbon burial. Notably, productivity peaked intermittently between 5.3 and 3.6 Ma, as indicated by the occurrence of suboxic species assemblages and increase in the abundance of Orbulina universa, benthic microfauna (ostracods), and other paleoproductivity indicators.

The Antarctic Circumpolar Current (ACC) represents the world’s largest ocean-current system and affects global ocean circulation, climate and Antarctic ice-sheet stability1–3. Today, ACC dynamics are controlled by atmospheric forcing, oceanic density gradients and eddy activity4. Whereas palaeoceanographic reconstructions exhibit regional heterogeneity in ACC position and strength over Pleistocene glacial–interglacial cycles5–8, the long-term evolution of the ACC is poorly known. Here we document changes in ACC strength from sediment cores in the Pacific Southern Ocean. We find no linear long-term trend in ACC flow since 5.3 million years ago (Ma), in contrast to global cooling9 and increasing global ice volume10. Instead, we observe a reversal on a million-year timescale, from increasing ACC strength during Pliocene global cooling to a subsequent decrease with further Early Pleistocene cooling. This shift in the ACC regime coincided with a Southern Ocean reconfiguration that altered the sensitivity of the ACC to atmospheric and oceanic forcings11–13. We find ACC strength changes to be closely linked to 400,000-year eccentricity cycles, probably originating from modulation of precessional changes in the South Pacific jet stream linked to tropical Pacific temperature variability14. A persistent link between weaker ACC flow, equatorward-shifted opal deposition and reduced atmospheric CO2 during glacial periods first emerged during the Mid-Pleistocene Transition (MPT). The strongest ACC flow occurred during warmer-than-present intervals of the Plio-Pleistocene, providing evidence of potentially increasing ACC flow with future climate warming.