Abstract
In this research, the Turonian-early Campanian sedimentary succession of the Abderaz Formation with 510 mthick (comprising: light grey shale and marls) was studied in the type section in eastern Kopeh-Dagh basin. The statistical analysis of the morphotype groups of the identified planktonic foraminifers shows that most of them are shallow water forms (SWF) and deep water forms (DWF). The high planktonic to benthic ratio indicates particular oligotrophic conditions and sedimentation in relatively deeper zones of a marine environment. The salinity of sea water during Coniacian was in the minimum level, whereas it reached maximum in Coniacian-Santonian boundary. Comparing Planktonic assemblages from the study formation with those from the Cretaceous biogeographical provinces reflects a close relationship between the identified species and the planktonic forms of the Tethyan provinces.
Highlights
Paleobathymetry is a significant environmental aspect of paleoceanography and paleoclimate reconstructions
Three groups of planktonic foraminifera were identified on the basis of different depth zones: epicontinental sea forms (ESF), shallow water forms (SWF) and deep water forms (DWF) [20,21,22,23,24]
1) Epicontinental sea forms (ESF) Species such as Heterohelix and Guembelitria that are associated with this depth zone have straight tests [3,25]
Summary
Paleobathymetry is a significant environmental aspect of paleoceanography and paleoclimate reconstructions. One of the main aims of this research is to analyse the geometric architecture of the tests of planktonic foraminifers, as well as the planktonic to benthic ratio, in order to reconstruct the sea level changes during the past. The sea level changes are reconstructed on the basis of [3] three swarming morphotypes (ESF, SWF, DWF), and planktonic to benthic foraminifera ratios. Many expert micropalaeontologists considered this ratio in measurements of the sedimentation depth [4] Initial researches about these analysis began between 1951 and 1955 [5,6], by determining the relationship between water depth and planktonic to benthic foraminifera ratios. In this research we use several different morphotype groups, especially deep water forms, to estimate the sea level changes in the study succession. We compared the frequency and dispersal of all cool and warm water fauna from the study sediments with those with Tethyan province affinities
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