Biostratigraphic and palaeoecologic study of the early maastrichtian-paleocene sediments in Kalecik region (Ankara-Turkey)‎

الملخص EN

In this study, the Gansserina gansseri (early Maastrichtian), Morozovella pseudobulloides, Morozovella trinidadensis (Danian), Morozovella angulata (Danian-Thanetian), Planorotalites pseudomenardii, Morozovella velascoensis (Thanetian) planktic foraminiferal zones and Arkhangelskiella cymbiformis (CC-25) (early Maastrichtian), Markalius inversus (NP-1), Cruciplacolithus tenuis (NP-2), Chiasmolithus danicus (NP-3) (Danian), Ellipsolithus macellus(NP-4), Fasciculithus tympaniformis (NP-5), and Heliolithus kleinpellii (NP-6) (Thanetian), calcareous nannoplankton zones were recognized from samples collected from the upper level of the Samanhk Formation and from the bottom to the top of the Dizilitaslar Formation.

These units represent the early Maastrichtian-Paleocene interval.

They were deposited in the turbidite facies of the southeast Kalecik region.

On the basis of trace fossil studiesThalassinoides isp.

(shallow marine) was identified in the upper level of the Samanlik Formation, and Helminthopsis isp.

(deep marine), and Ophiomorpha isp.

(shallow marine) were recognized in the bottom and middle levels ofthe Dizilitaslar Formation.

Results from studies of trace fossils, analysis of sedimentary composition, distribution of the numerical abundance of planktic, benthic foraminifera, and calcareous nannoplankton show that the upper levels of the Samanlik and Dizilitaslar formations were deposited with the characteristic proximal facies, whereas the lower and middle levels of Dizilitaslar Formation represent the proximal and intermediate facies of a submarine fan.

Lower Maastrichtian, Upper Danian and Thanetian were developed during a regressive period while the lower and middle Danian reflect alternating transgressive and regressive events.

Comparing palaeotemperature and palaeosalinity values which are calculated from delta(18)O parts per thousand and delta(13)C parts per thousand (PDB) from planktic foraminifera tests and percentage abundance as well as the diversity of temperature-sensitive calcareous nannoplankton groups, indicates that during the early Maastrichtian, the palaeotemperature and palaeosalinity of sea-surface water was relatively lower than during the Paleocene.

Palaeotemperature and palaeosalinity values started to increase from the early Danian onwards