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Bissekty Formation

Bissekty Formation
Stratigraphic range: TuronianConiacian
Type Geological formation
Underlies Aitym Formation
Overlies Dzheirantui Formation
Lithology
Primary Sandstone
Other Conglomerate
Location
Region Asia
Country  Uzbekistan

The Bissekty Formation (sometimes referred to as Bissekt) is situated in the Kyzyl Kum desert of Uzbekistan, and dates from the late Cretaceous Period. Laid down in the early the Turonian to Coniacian stages, it is dated to about 90-85 ma (million years ago).

The Bissekty Formation is characterised by a mix of marine, brackish, freshwater, and terrestrial animal fossils. This stands in contrast the strictly marine fossils found in the underlying Dzheirantui Formation, and indicates that the Bissekty was formed during the regression of a saltwater sea. The coastline expanded inland again in the upper portion of the Bissekty, represented by a proportional increase of fully aquatic species, which were almost completely absent from the middle period of the formation. Semi-aquatic species remained abundant during this middle period, and the geology of the formations indicates that a braided river system took the place of the coastline. Eventually the area was again completely underwater, during the time period represented by the later Aitym Formation, which preserves coastal marine sediments.

An indeterminate species of marine coral.

Linuparus

Linuparus dzheirantuiensis

Marine.

A spiny lobster.

An indeterminate species of marine placenticeratid ammonite. An indeterminate species of marine teredinid shipworm. An indeterminate marine trigoniid bivalve. An indeterminate marine veneroid bivalve.

Crassatelites

Indeterminate

A marine crassatellid bivalve.


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