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Donald G. Hadley

Publications and source records attributed to Donald G. Hadley.

9 recordsLinked to original sources
USGS1983

Middle Tertiary continental rift and evolution of the Red Sea in southwestern Saudi Arabia

Middle Tertiary rift volcanism in a continental-rift valley in the Arabian-Nubian Shield was the first surface expression of active mantle convection beneath an axis that was to become the Red Sea. Investigation of the coastal plain of southwestern Saudi Arabia suggests that the rift valley was filled with basaltic and felsic to rhyolitic volcanic rocks (Ad Darb and Damad formations), cherty tuffaceous siltstones (Baid formation), and subordinate Nubian-type quartz sandstone (Ayyanah sandstone) between about 30 and 20 Ma ago. These rocks are named herein the Jizan group. At the same time, alkali-olivine basalt was erupted on the stable Precambrian craton at locations 100 to 200 km east of the rift valley axis. First-stage spreading of the Red Sea began about 20 Ma ago when diabasic dikes and gabbro and granophyre plutons (Tihamat Asir complex) of oceanic-tholeiitic parentage were intruded into the continental-rift deposits. The new oceanic crust was injected into a region of thinned continental crust. Because of thinning, the continental crust was extended and became fractured into a series of fault blocks. Crustal extension in the attenuated zone was accompanied by mafic and silicic volcanism producing a continental rift-valley tectonic environment. Fault blocks of the rift valley were initially rotated toward the Red Sea during the first-stage spreading episode. Inland from the continental rift, the thick continental crust was distended on long parallel fractures that were intruded by gabbroic to quartz syenitic magma to form continental dikes. This period of continental-margin extension was short lived, lasting perhaps only 1 or 2 Ma. The first-stage sea-floor spreading of the Red Sea continued until about 15 or 14 Ma ago at a half-spreading rate of about 2.2 cm/yr. Throughout early Tertiary time, the Arabian Shield erosion surface remained near sea level. First-stage uplift of the Red Sea Escarpment began during middle Miocene time, as evidenced by the coarse polymictic boulder conglomerate of the Bathan formation. Second-stage scarp uplift and second-stage sea-floor spreading followed during Pliocene, Pleistocene, and Holocene time.

Open-File Report↗
USGS1979

Ultramafic inclusions and host alkali olivine basalts of the southern coastal plain of the Red Sea, Kingdom of Saudi Arabia

A variety of mafic and ultramafic inclusions occur within the pyroclastic components of the Al Birk basalt, erupted on the southern Red Sea coastal plain of Saudi Arabia from Pleistocene time to the present. Depleted harzburgites are the only inclusions contained within the basalts that were erupted through Miocene oceanic crust (15 km thick) in the vicinity of Jizan, whereas to the north in the vicinity of Al Birk, alkali basalts that were erupted through a thicker Precambrian crust (48 km thick) contain mixtures of harzburgites, cumulate gabbro, and websterite inclusions accompanied by large (> 2 cm) megacrysts of glassy alumina-rich clinopyroxene, plagioclase, and spinel. Microprobe analyses of individual minerals from the harzburgites, websterites, and cumulate gabbros reveal variations in composition that can be related to a complex mantle history during the evolution of the alkali basalts. Clinopyroxene and plagioclase megacrysts may represent early phases that crystallized from the alkali olivine basalt magma at depths less than 35 km. Layered websterites and gabbros with cumulate plagioclase and clinopyroxene may represent continuing crystallization of the alkali olivine basalt magma in the lower crust when basaltic magma was not rapidly ascending. It is significant that the megacrysts and cumulate inclusions apparently form only where the magmas have traversed the Precambrian crust, whereas the harzburgite-bearing basalts that penetrated a much thinner Miocene oceanic crust reveal no evidence of mantle fractionation. These alkali olivine basalts and their contained inclusions are related in time to present-day rifting in the Red Sea axial trough. The onshore, deep-seated, undersaturated magmas are separated from the shallow Red Sea rift subalkaline basalts by only 170 km. The contemporaneity of alkaline olivine and subalkaline basalts requires that they must relate directly to the separation of the Arabian plate from the African plate.

Open-File Report↗
USGS1972

Availability of low-sulfur coal in Fayette County, West Virginia

Fayette County is in central West Virginia. Rocks exposed at the surface are about 3,200 feet thick and comprise the Pocahontas, New River, Kanawha, and Allegheny Formations of Pennsylvanian age. The stratigraphic relations and distribution of coal in these formations were studied by the U.S. Geological Survey in connection with a low-sulfur coal program of the U.S. Bureau of Mines. The coal in Fayette County is medium-volatile and high-volatile A and B bituminous ranks. Of 51 coal beds in the county, 22 are 28 inches to as much as 9 feet thick and contain substantial reserves. Several coals have been mined locally in the past by underground, stripping, and auger methods. Of the 22 coals discussed, 17 contain less than 1.0 percent sulfur, and the remainder average less than 2.0 percent sulfur. Of an original 2,210 million tons of recoverable coal estimated for Fayette County, 678 million tons were mined between 1888 and 1966. Thus, the remaining recoverable coal reserves at the end of 1966 were 1,530 million tons. Of this amount, 86 percent or 1,320 million tons of coal is classified as low sulfur, and 210 million tons is classified as medium sulfur.

West Virginia↗