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

Chapter Five
Conclusion
foram became extinct below the K/T boundary at lower part or before the P.
hantkeninoides zone), where as the remaining 28 species became extinct at or
near the K/T boundary and (G. cretacea) with (H. monmothensis) crossed the
boundary and survived into the lower most part of Danian sediments. (The
occasion was applied on both Qulkqa and Sirwan sections also). This sudden
extinction is a catastrophic event may contain an evidence of asteroid impact.
The extinct species are from both of the large, complex and small tropicalsubtropical
forms. While the survivor species are of the small, cosmopolitan
and simple forms.
Consequently the data on stratigraphic range chart strongly imply that the
planktonic foraminiferal record across the K/T boundary transition can be explained
by earth derived environmental changes and that if an extraterrestrial bolide impact
occurred, its effect on marine plankton foraminifera was of the catastrophic
character that is usually assumed, which hesitated and terminated the Cretaceous
planktonic fauna in the studied area.
14- In general, benthonic foraminifera were little affected during the K/T
mass extinction which was distinguished by reducing the number of benthonic
species at all studied sections, at Plummerita hantkeninoides zone (CF1) and
increased again upward in (P1a) and (P1b)
15- The planktonic assemblages of the lower part from (CF8) to (CF1) in
Smaquli area and (CF5) to (CF2) at Dokan and Sirwan valley are characterized
by high values in the percentages of planktonic foraminifera, p/b ratios, species
richness, low Agglutinated percentages and general benthonic morphotypes of
Upper Cretaceous/Early Paleocene Paleodepth indicators reveal deeper water
bathymetry of upper bathyal around 300-600m. depth In Smaquli area, the
outer neritic-upper bathyal depth around 200-400m. depth in Dokan and Sirwan
area. Middle to outer neritic depth around 100-200m. lower part of Qishlagh and
inner to middle neritic depth 50-100m. in lower part of Kato section.
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