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At least 1,225 records · Page 68Linked to original sources
USGS1984

Reconnaissance geologic map of the Janban Quadrangle, sheet 20/44 B, Kingdom of Saudi Arabia

The Janban quadrangle, 20/44B, lies along the eastern margin of the Arabian Shield. The oldest rocks comprise the Precambrian Namtah Formation of the Halaban(?) group, and consist of basalt, dacite, siltstone, and calcareous greywacke metamorphosed in the lower amphibolite facies. Metamorphic rocks of uncertain Precambrian age in the northern part of the quadrangle are amphibolite, gneissic quartz diorite and metarhyolite that occur as roof pendants in plutonic rocks. Precambrian intrusive rocks, in order of decreasing age, are: biotite-hornblende tonalite; the locally gneissic Dawasir granodiorite and granite; the as Sabahah granite, coarse-grained alkaline granite; biotite-muscovite granite forming a small circular stock; the Janban granite, a coarse-grained non-foliated alkali-feldspar rapakiyl granite; aplitic granite; and fine-grained alkali granite that forms a stock, plugs, and dikes. Andesite dikes cut most of the plutonic rock units. Precambrian rocks are unconformably overlain by the Wajid Sandstone of Cambrian and Ordovician age, which covers the southeastern half of the quadrangle and consists of reddish-brown, medium-grained arkosic sandstone. Tertiary lake beds of gray marl, siltstone, and sandstone crop out locally, and lie unconformably on the Wajid. Most of the Wajid sandstone is mantled by an extensive blanket of Quaternary eolian sand and silt.

Open-File Report↗
USGS1985

Reconnaissance geologic map of the Jizan Quadrangle, sheet 16/42 B, Kingdom of Saudi Arabia

The Jizan quadrangle, bounded by lat 16°30’ and 17°00’ N. and long 42°30’ and 43°00’ E., is one of the southernmost quadrangles of the Kingdom of Saudi Arabia. It is named after Jizan, the largest city and principal port of the region, with about 30,000 inhabitants. Other significant towns and villages include Abu Arish, Al Madayah and Karbus, all linked to Jizan and adjoining quadrangles by paved roads. Most of the quadrangle is occupied by coastal plain bordering the Red Sea; one third is occupied by part of the Red Sea and the extreme northeast corner includes foothills of the Red Sea escarpment. The coastal plain, as much as 40 km wide, is covered by Quaternary surficial deposits overlying a sequence of Tertiary and Quaternary sedimentary rocks as much as 5 km thick. The only relief on the plain is provided by the Jizan salt dome, elevated about 50 m above sea level at Jizan city, and by small extinct volcanoes 100 to 150 m high near Abu Arish. The coastal plain is separated form islands, tidal mud flats and shallow lagoons. The sea is shallow, less than 200 m deep, and forms part of the shelf marginal to the main axial trough of the Red Sea. The high ground in the northeast of the quadrangle is formed by Jabal at Tirf, 452 m above sea level at its summit.

Open-File Report↗
USGS1985

Reconnaissance geologic map of the Muwassam Quadrangle, sheet 16/42 D, Kingdom of Saudi Arabia

The Muwassam quadrangle, bounded by lat 16°00’ and 16°00’ N. and long 42°30’ and 43°00’ E., includes the very southernmost territory of the Kingdom of Saudi Arabia. The quadrangle is named after Muwassam, a small town and minor border-crossing point for traffic into the Yemen Arab Republic. An asphalted road from the Jizan quadrangle to the north terminates at Muwassam town. Much of the quadrangle includes part of the Yemen Arab Republic and a portion of the Red Sea. All of the mapped area is occupied by coastal plain bordering the Red Sea. The flat coastal plain is covered by Quaternary surficial deposits overlying a sequence of Tertiary rocks as much as 5 km thick. The coastal plain is separated from the Red Sea by zone of supratidal sabkha deposits, offshore bars, islands, tidal md flats, and shallow lagoons. The sea is shallow, less than 200 m deep, and forms part of the shelf marginal to the main axial trough of the Red Sea.

Red Sea↗