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

Chapter Two
Lithostratigraphy
The upper contact of the red unit marked by starting of olive green and dark
grey lithology with the first appearance of 20cm hard well bedded sandstone at
the base of Tanjero Formation. The Tanjero Formation is represented by 72m
and subdivided lithologically into three distinct units based on field observation
Figs (2.12, 2.13) .These three units are described briefly as follows from the
base to the top.
- Unit A: 24m thick consists of olive green to dark grey shale alternate with
grey marl and claystone , with three layers of hard, fine to medium grain
sandstone at the base of 20cm thickness, middle part of 15cm thickness and
the upper part of 10cm. thickness.
- Unit B: 20m Consists of alternation of thin olive green beds of marl, dark
grey organic shale, papery calcareous shale and thin limestone beds of 3-6 cm
thickness, repeated in cyclic way every two meter in this interval and two
limestone beds of 20cm thickness at the middle and the upper part of this unit.
-Unit C: 28m Consists of dark organic papery shale and interlayred by thin
beds of dark grey marl with oily impregnated friable soft and weathered pale
brown three sandstone beds of 3m , 1.8m and 1m thickness at the upper part
of this unit respectively.
The overlying formation is Kolosh Formation of 49m thick consists mainly of
dark grey organic rich shale alternate with marl and thin layer of siltstone and
hard sandstone beds of 5cm to 10cm thickness, occasionally intercalated with
thin marly limestone layers and 5 red claystone beds at the last 10 meters of
the upper most part of Kolosh formation, which starts from 30 cm to 2m
respectively.
38