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

Chapter one
Introduction
4- Kato section: This section is located at 8 km to the southeast of Chwarta
town, (Barzinja area) Kato mountain, at latitude (35 0 40 - 39.1 = ) and longitude
(45 0 37 - 25.7 = ) near Suerala village (Fig.1, 1 & 1, 2)
5- Sirwan Section: located at the Sirwan valley, on the right bank of Sirwan
river (upstream of Diyala river), (2) km to the south of Kani Karweshkan
village, near Halabja Town at latitude (35 0 07 - 26.7 = ) and longitude
(45 0 52 - 34.7 = ). Most of the base part of type section for Tanjero Formation
was covered under water mass of Darbandekhan Dam. (Fig.1, 1 & 1, 2)
1.7.2 - Samlpe collection and preparation
All samples were collected from the studied sections at the field after
removing the surface contaminated soil and trying to obtain fresh and un
weathered materials. Samples were collected at interval range between (20 –
50) cm at or near the Cretaceous / Tertiary contact and at interval of 50cm to
3m away from the contact.
572 samples from five sections (Figs. 4.1-7) were analyzed for planktonic
and benthonic foraminifera, by using (50) gm from each sample. Three special
techniques were chose for the preparation and extraction of foraminiferal
content in this study:
1- Acetic acid method: The sample here was broken down into small
fragments of about 3 - 5 mm in diameter, placed in beaker. The small fragment
(soaked) in acetic acid. The prepared solution termed as ethanoic acid solution
CH 3 COOH, made up of (80%) acetic acid and (20%) H 2 O for the duration time
between (1 – 6) hours. The proposed technique based on cold-disaggregating
with acetic acid. The acetic acid causes a very slow reaction that
disaggregates the rocks without destroying and corroding fossil content. This
method firstly was used by (Lirer 2000). The time of desegregations varies
with the type of rock (amount of % CaCO 3 ) ranged between 1 – 2 hours for
marl , claystone and shale, 2 – 3 hours for shale and marly limestone, 4 – 6
hours are sufficient for limestone, this indicates that the porosity and degree
of lithification play an important role on disaggregation time.
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