Two glacial units have been identified within the Abu Mahara Group, with the upper being overlain by a 'cap carbonate' (the Hadash Formation). Ash beds from the lower glacial unit are dated herein by U-Pb zircon methods at 723+107-16 Ma. The Hadash Formation is succeeded by the Naftm Group which is overlain by the volcaniclastic Fara Formation. An ignimbrite unit within the Fara Formation is dated herein by U-Pb zircon methods at 544±3.3 Ma. The lithologies of the Nafun Group are found to indicate shallow marine deposits in the Huqf area of east-central, Oman and more distal deposits in the Oman Mountains of north Oman. The east-central Khufai Formation carbonates shoal-upward from mid-ramp settings to intertidal carbonates with outer-ramp carbonates in the Oman Mountains. There was arguably a slight draw-down in the uppermost Khufai Formation before the drowning of the carbonate ramp by the Shuram Formation siliciclastics. These red and green siliciclastics are typically swaley cross-stratified upward, indicative of storm deposition. An increase in carbonates in the upper Shuram Formation leads gradationally into the lower Buah Formation. The Buah Formation carbonates preserve another upward-shoaling trend from subwave base to sabkha deposits in east-central Oman. In Wadi Bani Awf, the coeval sediments are shown to contain slump structures and brecciated beds of the ramp slope, with thick breccia units representing slope failure deposits. The Oman Mountains therefore preserves the margin of a carbonate platform. The dramatic positive and negative to positive excursions recorded in the stable isotope stratigraphy through the Nafun Group are argued to largely reflect sea water δ¹³C signatures and may perhaps be explained in terms of climatic changes identified lithologically. The top of both carbonate formations are sequence boundaries with the maximum flooding surfaces identified within the siliciclastic formations.

The Lagonegro Zone comprises three structural units which outcrop within the pile of decollement nappes forming the southern Italian Appenines. Stratigraphic, structural and sedimentological evidence suggests that the zone represents the relics of a Mesozoic basin that developed amidst the carbonate platforms bordering the southern margin of Tethys. Mapping has confirmed that the Lagonegro I, Lagonegro II and Monte Foraporta Units are separated by thrusts and are stacked in ascending order. Middle Triassic fine-grained terrigenous clastic sediments and neritic limestone olistoliths of Lagonegro Unit II record the disintegration of a young carbonate platform under the influence of extensional tectonics. Deposition and redeposition of hemi-pelagic lime-mud washed from the adjacent shallow-water platforms during the Late Triassic is manifested in both Lagonegro units by the cherty limestones of the Sirino Formation; a gradual transition from calcareous to siliceous deposition at the top of the formation reflects the subsidence of the basin-floor beneath the Calcite Compensation Depth. Contrasting patterns of siliceous and calciclastic sedimentation developed during the Jurassic, probably imposed by renewed extensional tectonics; coeval calciclastic deposition in a small, and at times anoxic marginal basin is recorded in the Monte Foraporta Unit. Dolomitisation of basinal carbonate rocks took place during the Jurassic due to mixing of saline pore-fluids with meteoric water recharged from the adjacent carbonate platforms. Deposition of terrigenous shales below the Calcite Compensation Depth occurred during the Lower Cretaceous, but calcareous sedimentation was resumed in the Late Cretaceous and Palaeogene. The progressive deepening of the basin documented by these facies transitions is attributed to regional subsidence, caused by crustal extension and attenuation, and relative accretion of the surrounding platforms; comparable basal stratigraphies in several ophiolitic zones of the Alpine-Mediterranean region suggest that many Tethyan 'oceanic' basins may have initially developed in a similar manner.

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The Middle-Ordovician Simpson group, deposited in a shallow epicontinental sea, is composed of a sequence of interbedded limestone, shale, and smaller amounts of sandstone. By means of electric and radioactivity logs the group is divided into eight zones traceable across Pecos County, except for its absence, over the Fort Stockton uplift area, caused by post-Simpson erosion. Each zone thins persistently eastward toward the Texas Peninsula, which separated the West Texas basin from the Oklahoma basin of deposition. A northwestward increase in sand content of each zone indicates that the source area for the sand was to the northwest. In Pecos County oil is produced from the Simpson at present in only a small north-central area. / text

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