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

Chapter Three Biostratigraphy
CHAPTER THREE
BIOSTRATIGRAPHY
3.1: Preface
The comprehensive studies of planktonic foraminiferal biostratigraphy during
the last five decades have proved to be more useful and more accurate way
among the large number of micropaleontological branches, especially than
benthonic foraminifera for regional, interregional and intercontinental correlation
over the Cretaceous and Tertiary periods. A number of datum events and series
of zonation for different regions have been proposed. ( e.g. Bolli 1966; Postuma
1971; Blow 1979; Caron 1985; Berggren & Miller 1988; Berggren et al.,1995;
Berggren & Norris 1997; Keller 1988 , 2002, 2004; Keller et al 1995; Li & Keller
1998a,b; Abramovich et al., 2002; and Olsson et al., 2000). That is due to wide
geographic distribution, their occurrence in the deeper marine environment,
short geologic range as well as known morphological feature of the index
species.
3.2: BIOSTRATIGRAPHY
The samples which contain microfossils collected from the studied sections
yielded rare, predominant to extremely abundant groups, bad to well preserved,
according to different localities of studied sections. It is looked as the radiation
stage of biotic evolution and high diversity of globotruncanids, rugoglobigerinids,
globigerinids and heterohelicids planktonic foraminifera in Smaquli area (Gali
section), high to moderate occurrence in Qulka section (Dokan area), moderate
in Sirwan section and low occurrence, low diversity in both Kato and Qishlagh
sections with moderate calcareous and agglutinated benthonic forams in general
Table (3.1), (Figs.3.1 – 3.8). The foraminifera occurs continuously in the
sedimentary succession of the all studied sections, generally shows incessant in
sedimentary sequence without any interruptions, except of Sirwan section which
is evidenced by three diluted intervals of foraminiferal survivorship in the studied
upper part of Tanjero Formation, and the fourth one at the base of Paleocene
just after the extinction catastrophe of organism at the uppermost part of
Maastrichtian. The Upper Maastrichtian –Lower Paleocene interval in general
attracted particular attention because of the foraminifera is relatively moderate
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