[chondrichthyan fossils from Kyiv Paleogene: description]
All depicted fossils come from artificial sand inwashes. The sand was sucked out from the bottom of local lakes and comes mainly from Eocene epoch.
Sharks are represented by majority of their orders: Lamniformes, Carcharhiniformes, Hexanchiformes, Heterodontiformes, Squaliformes, Squatiniformes, Orectolobiformes and an extinct order Synechodontiformes. No distinguishable Pristiophoriformes teeth had been found yet. As usual for Eocene localities, vast majority of chondrichthyan remains belong to lamniform sharks. Some chimaeroids and myliobatiform rays are present as well.
Besides chondrichthyans, the sands contain remains of bony fishes, mammals, corals, molluscs, echinoderms, bryozoans, petrified wood and other fossils.
Typical set of local findings: a mixture of different geological ages is seen.
Shark teeth (1 of 28 is rather complete), belemnite rostrum, fish vertebrae, petrified wood, vole incisor (black and curved), Gastropoda and Bivalvia remains, coral sceleton, crinoid disk in a stone, ray tooth plate, some non-chondrichthyan teeth, simply nice stone.
(One lucky collecting day, 02 July 2007).
Evidently, absence of precise stratigraphic affixment of the fossils constitutes an essential problem. Some stratigraphic information can be obtained from local paleogeographic history (References), which is far from being continously marine.
The first sediments, which lay immediately on Precambrian granites, belong to upper Palaeozoic.
Carboniferous: first Phanerozoic rocks on adjacent territories (10−20 km to northeast). During most of the period, an alternation of continental and shallow-water conditions lasted (with marine transgression in Visean − Bashkirian ages). It gave sands, clays, limestones etc. The next sea regression occured in Moscovian age, and late Carboniferous deposits are absent at all.
Climate of near-Kyiv areas was close to tropical. And they were crossed by magnetic equator.
Permian: first Phanerozoic deposits at southeast Kyiv − continental (terrestrial and freshwater) sands and sandstones. Permian layers are thin and discontinuous, because Kyiv is on the border of their area of distribution.
The climate became quite dry.
Triassic period (except Upper): again some continental sands, sandstones and clays. And again their area of distribution comes to an end right here.
Aridity persisted and strenthened at the beginning of the period, but later diminished.
Jurassic deposits are the thickest: about 150 m. Bajocian age (Middle Jurassic) left continental gravels and sands (up to 40 m). Marine transgression in the next Bathonian age added 60−70 m of clays, in Callovian − about 50 m of clays, siltstones, sands and limestones. The sea persisted till Oxfordian (Upper Jurassic), when it left several meters of clays with limestones.
Lower and Middle Jurassic climate was humid, but in Oxfordian − Kimmeridgian it reached a new peak of aridity.
Cretaceous: next transgression began in Albian (Lower Cretaceous). The sea persisted till K/T boundary. It was deep only in Turonian − Coniacian (Upper Cretaceous). In Maastrichtian age, last in Mesozoic, here was a shore of shallow sea. Then the sea came away.
The climate remained rather dry in Cretaceous (except humid subtropical conditions in the middle of period − Aptian, Albian and Cenomanian ages).
Total thickness of Cretaceous deposits is 10−20 m.
Undoubted Mesozoic fossils are rare in Kyiv sands. They include belemnite rostra − scarce, broken and eroded due to redeposition.
Paleogene: during Paleocene the sea was absent. It returned in early Eocene and this time it left sands and some clays. Later (Lutetian − Bartonian ages) the sea deepened and deposited layer of sands with phosphorites, then marls and then noncarbonate clays. During Oligocene water became shallow again (sand and clay sediments). Total thickness of Paleogene layers is about 50 m.
Local climate was subtropical/tropical in Eocene and a bit more temperate in Oligocene.
At Paleogene/Neogene boundary the sea rapidly came away and did not return any more.
So, in Cenozoic the sea covered these places only during Eocene and Oligocene. Middle − Upper Eocene and all Oligocene sediments were later washed out by Dnieper river, and fossils from these layers were redeposited into the sands. Lower Eocene layers (lower Lutetian and all deeper) are untouched by the river and remain unaccessible. Respectively, the fossils in question are predominantly more young. But their composition shows, besides Eocene, some Cretaceous admixture. Probably, it's due to redepositions, which happened in Eocene; work of Quaternary glaciers is also not excluded.
I wish to thank:
to Pieter De Schutter for his help in identifying the teeth and a lot of valuable information;
to Henri Cappetta for identification and helpful information on the Orectolobiformes' teeth.
The site contains close-up images of local chondrichthyan fossils and is intended for information exchange on related themes with all interested.
Stereoimages are designed for cross-eyed viewing without any devices.
The fossils are not for sale.
S. Dobrovolsky, 2011−2021
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