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|Title: ||Geology of sakaka area northern Saudi Arabia with special emphases on palynology|
|Authors: ||Al-Ajmi, Hussain Fahad|
Northern Saudi Arabia
|Issue Date: ||Dec-2005 |
|Abstract: ||The study area is located at a part of the Shuwayhtyiah Quadrangle
and the other part is located at Al-Jawf quadrangle. In this area, the rocks
consist of continental to marine clastics, fine to medium-grained
sandstone, with a thin shaly layers interbeded. In addition, this area
includes another type of a stromatoletic, creamy limestone and a
yellowish semi-consolidated limestone rocks with shale, silt, gypsum and
some sandy in the form of thin interbeded layers.
Ash Shuwayhtyiah Quadrangle is located on the southeastern side of
the Sirhan –Turayf basin. A part of the studied area is included in this
quadrangle and the rest is located in the Jawf quadrangle, so this area
covers the outcrop of the four formations included in this study from
bottom to top as follows:-
1- Tawil Formation.
2- Jauf Formation.
3- Jubah Formation.
4- Wasia Formation.
The oldest rocks in this sequence is the Devonian Tawil Formation,
which is composed mainly of sandstone, The Jauf Formation overlies the
Tawil Formation, the contact between them is not exposed in the study
area, but it is exposed unconformablly between Qasr limestone, the
second member, of Al-Jauf Formation and The Tawil Formation in a
small part exposure at the top of Al-Adarea Mountain, 30 km north west
of Dawmat Al-Jandal. The Jauf Formation is divided into five members,
Sha’iba, Qasr, Subbat, Hammamiyat and Murayr Member so The Murayr
Member replaces the “transitional zone” at the top of the formation.. The
Middle Devonian Jubah Formation overlies the Jauf which consists of
sandstone and some shale.. The formation is assigned to the because of
the presence of Prototaxites sp., a tree-like algae which is restricted to
the Devonian period. This fossil has been collected from the lower
sandstone previously mapped as Wasia, but the upper part of this
sequence is a part of the Cretaceous Wasia because of the fossil
(Dinoflagellates), this fossil had been found in a rock samples collected
from the studied wells. The thickness of the Jubah Formation is 275 m in
Sakaka well and 198 m in Hazm Al- Jalamid well.
The Cretaceous Wasia Formation disconformably overlies the Jubah
Formation in the central part of Sakaka City and the contact between
these two formations is exposed at the bottom of the Za’bal Castle
mountain. It can be also seen at the northern part of Sakaka City near Al-
Nyhayan farms at the western side of beginning of the Sakaka –Ar’ar
highway, to west of the Al-Jubah Garden.
Fifty rock samples from the studied wells (Sakaka well and Hazm Al-
Jalamid well) were chemically analyzed for the Palynology study, and as
a result 193 species were defined 101 pollen grains species, and 92 spores
species, these fossils divided to two main microfloral assemblages as
1- Microfloral assemblages no.1 were found in Hazm Al-Jalamid well
at depth 550-748 meters and Sakaka well at depth 20 - 295 meters.
The palynomorphs in this assemblage consist of about 61.6%
pteridophyta, 33.1% gymnospermophyta and 5.3% unidentified
palynomorphs. These species are datable as Middle Devonian, the
thickness of the first zone in Hazm Al-Jalamid well is 198 m, and
275 in the second zone which refer to Sakaka well, which is the
thickness of Jubah Formation.
2- MIcrofloral assemblages no. 2 were found in samples from only one
well comprise: Sakaka well at depth 0-20 meters, but it was not
exposed in Hazm Al-Jlamid well. The palynomorphs in this
assemblage consist of about 49.3% pteridophyta, 26.1%
gymnospermophyta, 20.7% angiospermophyta and 3.9%
unidentified palynomorphs. This assemblage is distinguished from
the first assemblage by the decrease in the percentage frequency of
pteridophyta and gymnospermophyta, and the importance index is
the first appearance of the angiospermophyta. The palynomorphs
of this assemblage is most likely confined to the Late Cretaceous
which is 20 m in thickness in Sakaka well as a result.|
|Description: ||This study is conducted and submitted in partial fulfillment of the requirements of the Master's Degree in
Science Department of Geology at College of Science, King Saud University, Riyadh, kingdom of Saudi Arabia, Dhul-Qada 1426H-December 2005G|
|Appears in Collections:||College of Science|
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