Paleocene–Eocene Thermal Maximum Interval Research Articles

Chemostratigraphy of the Paleocene/Eocene (P/E) boundary sediments at Gabal el-Qreiya, Nile Valley, Egypt

In a detailed investigation of the sedimentology, mineralogy and trace element geochemistry of the stratigraphic interval spanning the Paleocene/Eocene (P/E) boundary in the Gabal el-Qreiya section, the author attempts to reconstruct environmental changes across the boundary especially for the interval representing the Paleocene-Eocene Thermal Maximum (PETM). The PETM interval consists of three distinct thin units of phosphatic shales followed by a calcareous phase. The basal unit is a laminated clay layer, whose base represents the base of the Eocene. It is enriched in silica and aluminium and is slightly phosphatic (bone-bearing). The middle unit is CaCO 3 -rich and bone-bearing, with a higher proportion of phosphatic components than the basal clay layer. The upper unit is coprolite-rich. These sediments contain different abundances of barite, Mn-oxide particles and grains of detrital origin. The PETM interval at Gabal el-Qreiya is characterized by high anomalies in most chalcophiles and REEs especially in the basal clay layer and the bone-bearing bed. It is concluded that these trace elements are incorporated into the phosphatic components (fish debris and coprolites) and organic matter. The three phosphatic shale units reflect euxinic marine environments and deposition in anoxic H 2 S-containing bottom waters rich in organic matter. The sedimentological, mineralogical and geochemical data show that the PETM interval represents deposition in a relatively deep water environment. However, it reflects slight fluctuations of sea level, a humid climate, high rain fall and oxidation conditions during weathering.

Foraminiferal and carbon isotope stratigraphy through the Paleocene‐Eocene transition at Dee Stream, Marlborough, New Zealand

Dee Stream in the Clarence River valley of New Zealand bisects a well‐exposed section of marine sedimentary rocks deposited in the early Paleogene at high southern latitudes. One hundred metres of strata lying within this section and comprising cm‐dm well‐bedded, siliceous limestone with marly partings was mapped, logged, and sampled to establish a detailed foraminiferal and carbon isotope stratigraphy and to examine environmental changes across the Paleocene‐Eocene thermal maximum (PETM). Although low abundance and poor preservation of planktic and benthic foraminifera characterises much of the Paleocene, foraminifera and carbon isotopes clearly show that the section spans the upper Paleocene to lower Eocene planktic foraminiferal zones from Zone P4 to Subzone P6b, and the Subbotina triloculinoides to Pseudohastigerina wilcoxensis Zones. The δ13 C record correlates closely to other δ13 C curves generated from other key early Paleogene carbonate sequences. The Dee Stream logged section contains a1m thick PETM interval at 26.5 m at the base of Zone P5, or the Morozovella velascoensis Subzone. Here, benthic foraminifera undergo significant extinction, Morozovella aequa makes its first appearance, and the δ13 C of carbonate decreases by 2‰. The benthic foraminifer Bulimina tuxpamensis dominates benthic assemblages immediately following the onset of the PETM interval, suggesting dysoxic bottom waters during this event. In conjunction with other recently examined sections from the Marlborough region, the thick and apparently continuous Paleogene record at Dee Stream provides an important site for understanding environmental change on high‐latitude continental margins during the Paleogene, including the PETM.

Effect of low temperature on hens' eggs : T. Moran ( Proc. Roy. Soc., London, Series B, 1925, 98, 436–456)

Despite the large number of studies on the Paleocene–Eocene thermal maximum (PETM), the knowledge of environmental and biotic responses in shallow marine environments remains quite poor. Benthic foraminiferal assemblages of the Sidi Nasseur and Wadi Mezaz sections in Tunisia were studied quantitatively and the paleoecologic interpretations provide new insights into the complex relationship between PETM global warming and perturbations of shallow marine settings. These sections expose upper Paleocene to lower Eocene shales and marls of the El Haria Formation up to the phosphate layers of the Chouabine Formation underlying the El Garia limestones. The Sidi Nasseur section contains a more complete and expanded Paleocene–Eocene boundary interval compared to Wadi Mezaz, although being truncated at the top. The Wadi Mezaz section contains a more complete post-PETM interval. The studied interval can be subdivided into a sequence of 4 biofacies, representing respectively a latest Paleocene biofacies, two PETM biofacies and one post-PETM Eocene biofacies.The latest Paleocene biofacies 1 consists of numerous calcareous benthic foraminifera (e.g. Anomalinoides midwayensis, Frondicularia aff. phosphatica and various Bulimina and Lenticulina species), abundant non-calcareous taxa (Haplophragmoides) and rare planktic foraminifera, indicating a slightly hypersaline eutrophic inner neritic to coastal environment, regularly interrupted by oxygen deficiency (moderate dysoxia). During the latest Paleocene, this highly productive environment shallowed as indicated by the increasing abundances of A. midwayensis. The variable dominance of non-calcareous agglutinated taxa in biofacies 1 indicates post-mortem dissolution effects. The TOC δ13Corg record reveals a sharp negative excursion, marking the base of the Eocene. In general, the absence of lithologic changes, an increasing sedimentation rate and absence of reworking indicate that the initial part of the PETM is complete and expanded in the Sidi Nasseur section. A sharp faunal turnover coincides with this negative δ13Corg excursion and is characterized by the disappearance or diminution of common Paleocene taxa in this area. During the PETM, benthic foraminifera are less abundant and consist of opportunistic non-calcareous taxa together with deeper dwelling (middle neritic) lagenids and buliminids (biofacies 2 and 3). Planktic foraminifera, dominated by flat-spired Acarinina (mainly A. multicamerata), become more abundant, as observed in many open marine sequences worldwide. All these faunal parameters suggest more stressed probably severe dysoxic sea floor conditions within a transgressive phase during the onset of the PETM. An estimation of the total duration of the Sidi Nasseur PETM interval is difficult to establish, yet the lack of recovery carbon isotope values suggests that the preserved PETM interval reflects only a part of the CIE “core”. The top of the PETM interval is truncated due to local (?) erosion during the early Eocene. The Eocene recovery fauna is mainly composed of Lenticulina and Stainforthia species (biofacies 4), indicating restricted coastal to hyposaline lagoonal eutrophic conditions, distinctly different from earlier environmental conditions.