Tectono-geomorphic development of intra-continental Cenozoic depressions within Cretaceous rocks of the Interior Homocli
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ORIGINAL PAPER
Tectono-geomorphic development of intra-continental Cenozoic depressions within Cretaceous rocks of the Interior Homocline, Central Arabia Abdullah O. Bamousa 1 Received: 14 November 2017 / Accepted: 28 August 2018 # Saudi Society for Geosciences 2018
Abstract Intra-continental depressions occurred in Central Arabia, within the evaporite-bearing Sulaiy Formation, and extends for over 550 km along N-S arcuate belt, passing through eastern Ar Riyadh, Saudi Arabia. They mark Jurassic/Cretaceous contact within the Interior Homocline of Central Arabia, accommodating Neogene and Quaternary deposits. Two en echelon major depressional areas were discovered, the northern major depressional area and the southern major depressional area. The first depressional area occurs between Al Artawiyah and Ad Dilam towns, following the arcuate Jurassic/Cretaceous contact. It contains five depressions: N-S Al Artwaiyah depression; NW-SE Ath Thumamah depression, northeast of Riyadh; NW-SE Jinadriyah depression, east of Riyadh; E-WAl Kharj depression; and N-S Ad Dilam depression. All five depressions seems to be formed by tectonic and subsequent geomorphic events, except for Al Artawiyah and Jinadriyah depression, which developed mainly by tectonic events. Southern major depressional area steps over to southwest of Ad Dilam, and occurs from Hawtat bani tamim to Layla towns. This Hawtah-Layla major depression trends N-S, and Cretaceous units strike NNE, which is a slightly oblique relationship, suggesting expression of deep-seated structures. Tectonic features were part of the Alpine-Himalayan orogeny, developing during Eocene. They followed by a geomorphic event (karsts and subsequent collapse) that took place during Mid Pleistocene. Ad Dilam depression is a surface expression of three oil and gas fields, while the southern major depression between Hawtat Bani Tamim and Layla towns is a surface expression of four oil and gas fields. Yet, other several depressional areas are also accommodating Quaternary desert sediments, and they contain economic resources, which therefore, worth further detailed studies. Keywords Sulaiy Formation . Al Butain depression . Central Arabia . Interior Homocline . Dissolution . Alpine-Himalayan orogeny
Introduction The Arabian Plate contains two major components, the Precambrian rocks of the Arabian Shield (1/3) in the west of the Arabian Plate and the Arabian Shelf cover rocks (2/3) in the east (Fig. 1). Paleozoic, Mesozoic, and Cenozoic (Paleogene) rocks of the Arabian Shelf are gently dipping 1° to the east, forming the Interior Homocline, and bound the Arabian Shield to the east (e.g., Powers et al. 1966; AlSharhan and Kendall 1986). The lower Paelozoic rocks are
* Abdullah O. Bamousa [email protected] 1
Geology Department, Taibah University, Madinah, Saudi Arabia
immediately underlain by the Arabian Shield in northern and southern unconformable contacts (Fig. 1). The northern contact separates Cambro-Odrovician clastic rocks such as Saq Formation, early Ordovician Qasim Formation, a
