Paleocene and Eocene Diatom Biostratigraphy and Taxonomy of Eastern Indian Ocean Site 752

Abstract

The Paleocene/Eocene boundary was recovered for the first time in diatom-bearing sediments at Broken Ridge, Site 752. Diatom assemblages are documented throughout the 180-m-thick sequence of upper Paleocene to lower Eocene sediments. Age control available from magnetostratigraphy, calcareous nannofossils, and planktonic foraminifers allows calibration of diatom datum levels to absolute time. A partly new/partly revised diatom zonation is proposed for the Paleocene/early Eocene based on the results of Site 752 and consideration of other studies. The diatom zones are defined as follows (from the youngest to the oldest): Pyxilla gracilis Zone (first occurrence of Craspedodiscus undulatus to first occurrence Pyxilla gracilis); Hemiaulus incurvus Zone (first occurrence Pyxilla gracilis to first occurrence Hemiaulus incurvus); Hemiaulus peripterus Zone (first occurrence'Hemiaulus incurvus to first occurrence Hemiaulus peripterus var. peripterus). Three new taxa are described: Anaulus fennerae n. sp., Stictodiscus bipolaris n. sp., and Hemiaulus peripterus var. longispinus n. var.

The Paleocene record of marine diatoms in deep-sea sediments

“…4) seems to show an abrupt decrease in the earlier Eocene, with diversity remaining low until the middle Eocene. Given the scarcity of data during this time period -only a few samples were studied here for the early Eocene and barely 15 samples come from a single site (752A from Fourtanier, 1991) were retrieved from NSB -it is entirely possible that this decrease is artificial. In fact, reports from the Paleocene-Eocene transition on the Russian epicontinental platform (Oreshkina and Oberhaensli, 2003;Oreshkina and Aleksandrova, 2007;Oreshkina, 2012;Oreshkina and Radionova, 2014) reported floral changes during the earliest part of the Eocene, such as the loss of various Cretaceous species, but also the appearance of new Eocene species.…”

“…Despite those small differences (namely a flatter late Oligocene), the primary pattern after the early Eocene remains unchanged from Wiese et al (2016). Making an age model for Site 752A in this study also allowed for the addition, in the black diversity curve, of the Fourtanier (1991) data set.…”

“…While diatom-bearing land sections are known from this time period (Harwood, 1988;Homann, 1991;Fenner, 1994;Hollis et al, 2017), in particular on the Russian platform (e.g. Jousé, 1949Jousé, , 1955Oreshkina and Aleksandrova, 2007;Aleksandrova et al, 2012;Radionova et al, 2003;Oreshkina and Radionova, 2014), then an epicontinental shallow sea, few diatom-bearing Paleocene sediments have been retrieved or studied from the deep sea (Mukhina, 1976;Gombos Jr., 1977Fenner, 1991Fenner, , 2015Fourtanier, 1991).…”

The Palaeocene–Eocene Thermal Maximum super greenhouse: biotic and geochemical signatures, age models and mechanisms of global change

“…Diatom records through the PETM are also rare. ODP Site 752 in the eastern Indian Ocean recovered a diatom-bearing PETM succession, but only biostratigraphical and taxonomical work has been done on this material (Fourtanier 1991). A considerable turnover of the diatom flora at generic and species levels has been observed in sections from the epicontinental sea in Russia, including the appearance of short-lived taxa (Radionova et al 2001;Oreshkina & Oberhänsli 2003).…”

Thai amber: insights into early diatom history?

“…Diatom assemblages including Hemiaulus are known mainly from the Russian Platform in a context of epicontinental shallow sea basins (for reviews of the sites see Jousé, 1978, Oreshkina andRadionova, 2014), from the Fur Formation, Denmark (Homann, 1991;Fenner, 1994) and Seymour Island, Antarctica (Harwood, 1988). Hemiaulus is recorded from several deep-sea drilling cores from the Atlantic, Pacific and Indian Oceans (for lists of sites see Fourtanier, 1991b;Renaudie et al, 2018). During the Paleocene Hemiaulus was represented by a plethora of species and had a geographic distribution in both the southern and northern hemispheres, both in epicontinental seas and in more open oceanic environments.…”