Early Paleogene transgressions: Stratigraphical and sedimentological evidence from the northern Peri-Tethys

Abstract

Our study in lithologically diverse lower Paleogene deposits of the former southern USSR and West Siberia resolves three sedimentary provinces: (i) Southern (Crimea-Caucasus and Central Asia), dominated by biogenic calcareous sediments of the deepest basinal portions; (ii) Transitional (southern Russian craton and Turan plate), displaying calcareous and siliceous clayey deposits; and (iii) Northern (central Russian craton and West Siberian plate), showing biogenic siliceous and terrigenoussiliceous sediments of basinal margin.We used standard and regional scales based on seven microfossil groups (planktonic and benthic foraminifers, nannoplankton, radiolaria, diatoms, silicoflagellates, and dinocysts) to correlate various sediment facies among ∼ ∼80 reference sections across the study area. Correlation was performed for the Transitional province, where the presence of both calcareous and siliceous facies affords the use of calcareous and siliceous planktonic and dinocyst scales with varying resolutions. Besides, in the Transitional province, we established regional sedimentary cycles corresponding to the late Thanetian, Ypresian, and late LutetianBartonian. These cycles are traceable into the Northern province, enabling us to determine or refine ages of the sequences, and into the Southern province.Each sedimentary supercycle falls into three units, often with hiatus at the base, correlatable to 3rd order eustatic cycles and featured by distinctive facies. The facies succession appears to reiterate through the upper Thanetian, Ypresian, and upper Lutetian-Bartonian cycles.The lower units of each supercycle are composed of calcareous sediments rich in nannofossils and foraminifers and are traceable from the Southern province into the Transitional province, the late Lutetian unit extending as far as the Northern province. 239Radionova, E.P.,

Paleogene evolution and demise of the proto‐Paratethys Sea in Central Asia (Tarim and Tajik basins): Role of intensified tectonic activity at ca. 41 Ma

“…The 2nd Paleogene sea incursion in the Tarim Basin appears also coeval with the fluctuations in the Siberian Sea where a transgression during the Lutetian (starting at ca. 47 Ma) is reported by Radionova et al () (Figure ). During this interval, an increase is indicated in the global sea level reconstruction curve of Haq et al ().…”

“…Regional coastlines and depositional environments during the maximum Paleogene sea advances and retreats were drawn based on the results of this study and integrated with existing literature. The updated palaeo‐reconstructions of Poblete et al () integrating continental reference points, palaeotopography and shorelines were updated with data from the Darius project (Barrier et al, ), Peri‐Tethys atlas (Dercourt et al, ), the compilation of Bosboom et al () and palaeogeographical changes in the Turgai Strait and West Siberian Sea were drawn based on Radionova et al (), Akhmetiev and Beniamovski (), Akhmetiev et al ().…”

“…The 1st Paleogene sea incursion at ca. 59 Ma appears coeval with the Thanetian transgression in the northern Peri-Tethys sedimentary provinces (Radionova et al, 2003) (Figure 12) and the onset of a long-term global sea level high (black dashed lines in Figure 9) suggesting eustatic forcing of the 1st sea incursion. Subsequent Thanetian-Ypresian short-term global sea level fluctuations (blue curve on Figure 9) (Kominz et al, 2008) and the Ypresian fluctuations in the West Siberian Sea (Radionova et al, 2003) have not (yet) been identified in the Tarim Basin.…”

Early to middle Eocene history of the Arctic Ocean from Nd‐Sr isotopes in fossil fish debris, Lomonosov Ridge

“…Tectonic reconstructions of the early Paleogene Arctic [Lawver et al, 2002;Thiede and Myhre, 1996] have suggested that deepwater exchange between the Arctic and the world ocean was much more restricted than it is today. There was probably a shallow intermittent connection between Tethys and the Arctic via the western Siberian seaway (Turgay Strait [Radionova et al, 2003]) through the end of early Eocene time (Figure 2), and possibly into the early part of the middle Eocene [Onodera et al, 2008]. The water depth of this connection is unknown; however, with the lack of any significant land ice during the warmest part of the Eocene, sea level may have been 70-80 m higher than it is today [Miller et al, 2005a].…”

First molecular scombrid timetree (Percomorpha: Scombridae) shows recent radiation of tunas following invasion of pelagic habitat

“…2013.775366 Horizon is a major disoxic level originating after the Lutetian/Bartonian transgression, which has been assigned to the CP14 nannoplankton zone and Subbotina turkmenica foraminiferal zone (40-39 Ma; Radionova et al 2003). The indeterminate gempylid taxon from the Campanian (79.66 Ma) Coffee Sand Formation, Griffin Sandpit, Mississippi (Nolf & Stringer 1996) is used to establish an upper boundary.…”