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

Chapter Four
Depositional Environmenment and Paleoecology
The remaining interval of this section is represented by thick succession
115m. of Aqra limestone Formation ,characterized by common occurrence of
coral like rudists which constitute the original part of the carbonates with other
great number of bivalve pelecypods, in addition to the echinoids, gastropods,
brachiopods, coral and large foraminiferal assemblages with common smaller
benthonic too. (Fig. 4.6) It is convenient to mention that the occurrence of
Planktonic foraminifera not observed till the end of this section except for the
lowermost few meters of this interval. It is well known that rudist growth and
their nourished during late Cretaceous shallow marine quiet environment with
low agitation or dynamic action of watermass within depositional environment,
the bathymetry not exceeds than 30m depth. The Aqra interfingering limestone
represents submerged high reefal facies relatively represent a time span of
quite and shallowing within the mobile foreland basin of Tanjero trough. (Al-
Omari 1989, Al-Mutwali 1992, Lawa et al., 1998.)
The Aqra Limestone Formation followed by 67m. of alternation of bluish
white marl, marly limestone, siltstone, recrystallized fossiliferous limestone
sandy limestone, with weathered friable sandstone, olive green sandstone,
dark grey shale and calcareous shale. This interval characterized by
continuation of the same benthonic foraminiferal assemblages of Aqra
Limestone without macrofossils growth in situ ,it is characterized by increasing
in agglutinated percent from 20 to 45 in the middle and upper part of this
interval. The depositional environment and paleobathymetry of this unit may
represent upper part of inner neritic shoal from 10 to 30m. depth. This interval
characterized by no evidence of any porcelaneous foraminiferal assemblages
which indicate no restriction, high agitation of watermass, and high rate of
deposition which may cause the dilution of planktonic foraminiferal
survivorship.
The planktonic assemblages of the lower part in Kato section from (CF4)
Zone to lower most part of (CF3) Zone (Fig. 4. 7) are characterized by low to
moderate values in the percentages of planktonic foraminifera, P/B ratios
98