Devonian Jauf Formation, Saudi Arabia: Orbital Second-order Depositional Sequence 28

Abstract

ABSTRACT The Devonian Jauf Formation (Huj Group) froms part of a regional transgressive-regressive depositional sequence that extends more than 1,500 km across the Arabian Platform from the Al Jawf outcrops in northwest Saudi Arabia, to the subsurface of eastern Saudi Arabia and Oman (Misfar Group). The formation ranges in thickness from 200–335 m in eastern Saudi Arabia to about 300–330 m in northwest Saudi Arabia. It disconformably (?unconformably) overlies the continental to shallow-marine Tawil Formation, and is unconformably overlain by the continental Jubah Formation. The Jauf Formation consists of five members that are apparently conformable; from base-up: Sha’iba Shale, Qasr Limestone, Subbat Shale, Hammamiyat Limestone and Murayr. In the Al-Qalibah reference section, it is divided into 21 informal units. The Early Devonian Emsian Hammamiyat Member represents the main marine flooding event; it consists of Hammamiyat units 1–6 each characterized by a clastic section that is capped by limestone. The Jauf Formation is interpreted as an orbital second-order depositional sequence (denoted DS2 28), which is bounded by two second-order sequence boundaries: SB2 28 = Jauf/Tawil (c. 407.6 Ma) and SB2 27 = Jubah/Jauf (c. 393.0 Ma). The Jauf Formation appears to consist of six third-order depositional sequences (DS3 28.1 to 28.6) that were deposited in the Early Devonian, ?Pragian and Emsian stages The Hammamiyat Member (DS3 28.4) is interpreted to consist of six fourth-order orbital cycles (DS4 28.4.1 to 28.4.6) each deposited in 0.405 million years.