Magdy Torab*
*M. Magdy Torab
* Prof. of Geomorphology, Department of Geography, Alexandria University, Faculty of Arts, Damanhour, Egypt
E-mail: magdytorab@hotmail.com.
There are strong relationship between Global sea level and the Earth's climate. So changes in sea level are one of the most characteristic phenomenon of the Quaternary Period. This paper dealt with the change in the sea level at the "Musandam" Peninsula in the far North of the Sultanate of Oman (figure 1). Field studies for the western and eastern coasts of "Musandam" Peninsula showed that there are some geomorphological evidences of the Quaternary sea level changes such as raised wave-cut terraces on cliffs, marine caves, paired fluvial terraces and Knick Points on dry valleys channels, valley in valley shape on cross section profiles, and hanging dry valleys (wadies). All these features were created during former intervals of high sea level; the highest marine and fluvial terraces represent the oldest sea-level high stand. Because the "Musandam" Peninsula is slowly rising, terraces cut during an interglacial continue to rise with the area during the following glacial interval. When sea level rises during the next interglacial, a new wave-cut terrace is eroded below the previous interglacial terrace. Geologists can calculate the height of the former high sea levels by knowing the tectonic uplift rate of this area.
The "Musandam" Peninsula is in the far north of the Sultanate of Oman, embossed into the Strait of Hormuz at the entrance to the Persian Gulf (Figure 1). "Musandam" Peninsula takes the shape of an acute-angled isosceles triangle, it’s head lies on the strategic strait of Hormuz. The nearest point to Iran across the strait is not more than 55 k.m and does not exceed 60m in depth. The "Musandam" Peninsula has two coasts: western coasts located on the Persian gulf, while it’s eastern coast lies on the gulf of Oman (Indian Ocean).
The “Mosandam” mountains rise straight out of the sea giving rise to the fiord-like appearance of the coast, It is formed during the Cretaceous and Miocene ages. The mountains originally constituted part of the Zagros Mountain range, but with earthquakes and volcanic activity, separated to form the Hajar Mountain range.
Rocks of the Hajar super-group in the north are actually folded in a north-south trending anticline. Thinly-bedded yellowish-orange dolomitic limestones and mudstones indicating a near-shore environment progress upwards into highly fossiliferous shelf limestones. Shell fragments, brachiopods and micro-fossils in limestone indicate continental shelf conditions. These limestones were deposited from the early Jurassic to the Cretaceous period and are reckoned to be older than 65Ma.
Previous studies related to the area had been carried out by Falcon (1972 and 1973), Vital Finzi and Cornelius (1973 and 1982), which suggested the sinking of marine terraces below sea-level as a result for the terrestrial descending movement experienced by the Peninsula during the Quaternary period. Results also clarified that there were no evidences for the existence of rising shores in the Peninsula (Falcon, 1973, p. 3).
The Quaternary sea-level changes in Musandam is recorded in the geomorphology of ancient coastal cliffs, terraces, and semi arid valleys (wadies), found both above and below present sea level, but this study is dealing with the rises features above present sea level.
References
Falcon,N.L., 1972:
“ Expedition to unknown Musandam”, Geographical Magazine,pp.105-111.
--------------, 1973:
“The Musandam Northern Oman expedition ,1971-72”, Geographical Journal, 139,pp.1-19.
Vital Finzi,C. & Cornelius, P.F.S., 1973:
“Cliff sapping by mollusks in Oman”, Journal of sedimentary petrology,43,1,pp.31-32.
-----------------, 1982:
“Recent coastal deformation near the strait of Hormuz”, Proceedings of the royal geographic society, London, pp.441-457.
Fig. 1: Location of Musandam peninsula