biostratigraphy and paleoecology of cretaceous/tertiary boundary in ...

Chapter Four
Depositional Environmenment and Paleoecology
enable much more sophisticated testing of those observations in such
biostratigraphic analysis nevertheless on high resolution results for favorites.
Consequently to avoid and reduce the effect of such variability we tried to get rid
of these sophisticated cases by organization and systematic work with relevant
and accurate documentation of biostratigraphic evidences.
4.4- Planktonic/Benthonic foraminiferal ratio and Benthic Foraminiferal
Assemblage
In the present study, among the most important paleoecological and
depositional environment factors, the abundance of planktic foraminifera,
planktonic species richness, Planktic/Benthic foraminiferal ratios, Benthic
Foraminiferal assemblage, and Agglutinated/Calcareous ratios are used as
important parameters to interpreting paleoecological changes and
paleobathymetric determination of Maastrichtian/Lower Paleocene
succession in Sulaimani region (Figs 4.3 - 4.8)
Nyong & Olsson, 1984 (in Samir, 2002) have noticed that the inner shelf
depth 10-50m is characterized by low planktonic percentage with low
species diversity and high benthic foraminiferal assemblages, whereas
higher 8-25% planktonic foraminifera and diversity characterize the middle
shelf depth 50-100m. In addition, the outer shelf depth 100-200m is
characterized by 30-70% planktonic foraminifera, while the middle slope
depth 400-800m is characterized by 90% planktonics and a slight increase
in benthonic diversity.
The ratios of Planktonic/Benthonic foraminiferal species are a valuable
indicator of paleobathymetry. The general conventional pattern for benthonic
foraminiferal raises from the nearshore environment to the continental edge,
further downward decreases significantly towards bathyal depths (Van Der
Zwaan et al., 1990).
According to benthonic foraminiferal assemblages, many authors
recognized two main cosmopolitan distinct, depth-controlled benthic
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