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

Chapter Four
Depositional Environmenment and Paleoecology
4.7- Sedimentation rate around Cretaceous/Tertiary boundary
Sediments principally consist of two different components: -Allochthonous
clastic or detrital sediments which are derived from land sources outside of
depositional area.-Autochthonous, sediment produced in the depositional area
mostly biogenic or chemically precipitated sediments. The sedimentation rates
of clastic sediments are controlled mainly by the size and characteristics of the
source area. Furthermore, the distances of the depositional area from the site
of sediment input play a role. The sedimentation rates of sediments on
siliciclastic shelf or foreland basin were proposed by several authors from low
rate of deposition by 10m/ma to high rate of deposition by 100m/ma, in (Ensele,
2000, Fig, 10.3, page. 458)
The magnetostratigraphy of Maastrichtian and lower Paleocene showed
magnetochrons 32n to 28n (Figs 3. 12, 3.13). These paleomagnetic data are
available to determine and calculate the sedimentation rates of the studied
sections and establishment the chronostratigraphy of the Cretaceous/Tertiary
boundary events as mentioned in previously discussed chapter three.
To identify the presence of possible hiatuses, due to the non
documentation of some zones and the overall poor recovery, high rate of
sediment accumulation in thick interval of biozones, or thin interval of slow rate,
non deposition and condensed sections, the high resolution planktonic
foraminiferal biostratigraphic zonation plays an important role in determining
such sedimentary rate with the aid of paleomagnetic Chron, the age and
duration of each faunal event and the age of datum events achieved by several
authors in the study of high resolution biostratigraphic zonations around
Cretaceous/Tertiary boundary in different localities of the global Earth.( e.g:
Berggren et al., 1995; Berggren & Norris, 1997; Li & Keller,1998a,b;
Abramovich et al., 2002; Olsson et al., 2000); Keller, 2002, 2004; (Figs 3.12-13)
The mean sedimentation rate or average sediment rate by biozone
(m/myr) or years/meter was estimated previously. In this chapter just try to
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