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

Chapter Three Biostratigraphy
3.2.2.3- (Pá & p0) in Dokan and Sirwan valley.
In the present study, the earliest Paleocene P0 (Guembelitria cretacea)
Zone, and Pá Parvularugoglobigerina eugubina Zone) which is well observed
in Smaquli area, was not recorded completely or continuously in both Qulka and
Sirwan sections
The Cretaceous/Tertiary boundary in Dokan area placed on the base of soft
weathered friable fine sandstone and claystone of 5 meter thickness with very
rare occurrence (Few individuals) of Guembelitria cretacea Cushman and
Globoconusa daubjergensis (Bronnimann) recorded from the upper most part of
this sandstone unit (Fig.3.5). As in Gali section, the base of this fine sandstone
marks the extinction (Datum event) or disappearance of Cetaceous planktonic
foraminifera
While in Sirwan valley, the Cretaceous/Tertiary boundary placed on the
base of 3 meters of pale grey to yellowish, weathered friable conglomerate. This
conglomerate and overlying 12 meters of dark grey organic rich shale alternate
with marl, marly limestone and thin layer of siltstone, sandstone, are barren of
foraminifera, as mentioned previously in Chapter Two that the sedimentary
succession of the studied sections in Sirwan valley shows evidence of 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 age estimation of this interval depending on Magnetic polarity and
recorded datum events by (Olsson et al., 2000), (Keller 2002, 2004), with the
time span of (65.00Ma) end of Plummerita hantkeninoides to 64.90Ma last
occurrence of Parvularugoglobigerina eugubina, estimating absolute ages based
on magnetochron ages. 100 Ky with 20 Ky/m high rate of deposition in Qulka
section. And with 6.5 Ky/m high rate of deposition in Sirwan section (Figs. 3.12-
13)
Sedimentologically any evidence of erosional surface, condensed section or
mineralogical record, trace fossils or hard ground was not observed beside
these significant points, the great lithologic similarity between both Tanjero and
overlying Kolosh Formations in which no one can observe or distinguished the
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