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

Chapter Two
Lithostratigraphy
In the Kato section Tanjero Formation is underlained by Shiranish
Formation gradationally, as a rule the contact is marked at the first appearance
of gray sandstone or siltstone beds at the top of Shiranish Formation. The
Red Bed Series overlies the Tanjero Formation conformably with a transitional
contact. The studied Cretaceous part in Kato section is divided into three units.
Unit one comprises 40m of thick bedded succession of fossiliferous limestone
and interbedded calcareous shale, the limestone forming a ridge of massive
pale grey, tough, recrystallized, occasionally dolomitized, and characterized by
several bands rich in rudist, gastropods, pelecypods, brachiopods, and other
macro and microfossils. This unit was mentioned previously as interfingering
Aqra limestone by Al-Mehaidi (1975) and Lawa et. al., (1998). The Aqra unit is
overlained by 35m of alternation of thin bedded pale grey limestone, grey
shale, marl, friable sandstone and calcareous fossiliferous sandstone with
claystone and detrital fossiliferous limestone of second unit (Tanjero
Formation). The third unit represents a transitional interval between Tanjero
Formation and Red Bed Series; it comprises 23m of alternation of thin bedded
pale gray unfossiliferous limestone, olive green sandstone, red clay, friable
reddish sandstone, siltstone, and detrital sandy reworked fossiliferous
limestone at lower part, and dark organic rich shale bed of 20 cm thickness at
the base of this interval. The lower part of the Red Bed comprises alternation
of thick bedded, red claystone, friable red bed of sandstone and siltstone, with
lenses of conglomerate. The contact placed on the line when the olive green
colour of sediment is vanished and the appearance of completely red colour of
sediment and conglomerate beds.
2.4 - Lithostratigraphy of Qishlagh section
The exposed rocks of Qishlagh section appeared in Qala Cholan area figs
(2.6, 2.7) which includes the upper part of Tanjero Formation and the lower
most part of Red Bed Series, the lithologic nature comprises of 45m of flysch
type of Tanjero clastic sediments with dark grey to olive green marl, shale, and
bluish white calcareous marl and thin layer of fossiliferous friable sandy
limestone intervened by streak of limestone at the base of this interval, this
unit followed by 115m of interfingering Aqra Limestone which consists of
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