عنوان

Stratigraphy and sedimentology of the cover rocks of the Maqna area, Saudi Arabia

Number

TLets796649

Title Proper

Stratigraphy and sedimentology of the cover rocks of the Maqna area, Saudi Arabia

General Material Designation

[Thesis]

First Statement of Responsibility

Taj, Rushdi Jamal

Name of Publisher, Distributor, etc.

University of Glasgow

Date of Publication, Distribution, etc.

1991

Dissertation or thesis details and type of degree

Thesis (Ph.D.)

Text preceding or following the note

1991

Text of Note

The Maqna area, part of the Midyan Peninsula, is characterized by well exposed synrift sediments of Oligocene and Miocene age which can be grouped into four formations: the Sharik, Musayr, Nutaysh and Bad Formations. These mark steps in the geodynamic evolution of the Red Sea associated with sea-floor spreading. The early Sharik Formation consists of fan delta sediments. It covers much of the northern half of the area and deposition was associated with the first movements along the Arabian Wrench Fault which caused the down-faulting of the Midyan peninsula. The Musayr Formation is divided into Lower Gypsum and Upper Limestone members. The Musayr Gypsum is a coastal lagoonal evaporite sequence and has a restricted (L-shaped) distribution along northern and western side of Jabel Tayran. Five lithofacies assemblages are identified in the Limestone sequence. These are: (I) conglomeratic limestone; (2) laminated limestone; (3) oyster limestone; (4) sandstone; and (5) brecciated limestone. The Musayr Limestones are marine sediments (previously known as reefal limestones) deposited in environments ranging from near-shore to slope. Macrofossils present indicate Mediterranean affinities. Two corals, species of Acanthastrea cf. echinata and Lithophyllia michelotti, are assigned the Burdigalian (Lower Miocene). The Nutaysh Formation is interpreted as a turdidite sequence with proximal coarse grained conglomerate and sandstone sediments concentrated in the northern and western parts of the Maqna area, while towards the southeast, distal fine grained marly sediments are predominant. The capping sequence, the Bad Formation, is a shallow-water deep-basin evaporite. Deposition of the evaporite sequence was followed by the second movement of the Arabian Wrench Fault, post Miocene-Pliocene, which resulted in emergence of the area and local deposition of tufa. The Quaternary coastal limestones and coarse braid delta sediments, a continuation of inland clastic terraces, may reflect tectonic controls related to eustatic falls in sealevel. The Tertiary formations of the Maqna area contain similar cycles of diagenetic sequences which indicate that burial resulted in similar general diagenetic environments.

Taj, Rushdi Jamal

University of Glasgow

Electronic name

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[Thesis]

276903

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