ABSTRACT The most common and widespread sedimentary facies of Pleistocene Lake Bonneville, in the eastern Great Basin of North America, is marl, which consists of a mixture of fine-grained endogenic calcium carbonate that precipitated in the epilimnion of the lake and then settled onto the lake floor and mixed with fine-grained clastic sediments. Primary sources of clastic sediment were inflowing rivers, wave activity in shore zones, and ice rafting. The thickness of deposits in cores and outcrops is largely dependent on the proportion of clastic sediment, although the rate of endogenic calcium carbonate precipitation probably also varied temporally and spatially. Net sediment-accumulation rate in the marl, as measured in outcrops and cores, ranges from a low of 4 cm/1000 yr, in the middle of the lake basin far from sources of clastic input, to over 100 cm/1000 yr near clastic-sediment sources. Underflow deposits, derived from higher-density river water loaded with suspended sediment, are thick and extensive near the mouths of major rivers that drained glaciated mountains. Net sediment-accumulation rates in suspended-load underflow deposits were much greater than those in contemporaneously deposited marl. The largest underflow-sediment accumulations, which have a fan shape in plan view, have been referred to as deltas (as at the mouths of the Sevier, Provo, Weber, and Bear Rivers). True Gilbert-type deltas composed of gravel, with topset, foreset, and bottomset beds, are uncommon in the basin. Variability in the sedimentary characteristics of the Bonneville deposits is determined by geomorphic factors, such as wave energy, composition of surficial material in the shore zone (e.g., resistant bedrock vs. unconsolidated alluvium), slope, and proximity to river mouths and active shore zones.

Abstract This chapter summarizes the tectonic events that have affected the region of the Arabian Intrashelf Basin and the development of the intrashelf basin. Precambrian–Infracambrian fault systems provided a structural framework, which was later reactivated during the Late Paleozoic. Further development along the structural trends continued in the Triassic and Early Jurassic with the development of an Early Jurassic tectonically controlled intrashelf basin. The accommodation space was filled with Dhruma Formation carbonates by the early Bathonian, resulting in a broad and fairly flat platform. A crucial factor is how suppressed tectonism was during the Mid- and Late Jurassic. The intrashelf basin developed on the broad, tectonically stable Tethyan passive margin continental shelf 200--300 km distant from the Tethyan outer shelf edge. During the Mid- and Late Jurassic, this tectonic stability provided the foundation for a broad, stable Tethyan continental shelf region at least 1000 × 1200 km in area, far removed from siliciclastic sources, within which the huge Arabian Intrashelf Basin formed and the sequences of carbonate rocks and evaporites that created the Jurassic hydrocarbon system were deposited. Tectonism during the Mid- to Late Jurassic evolution of the Arabian Intrashelf Basin initially included only moderate subsidence. There was subtle uplift along some of the structural trends in the Late Jurassic and uplift and westwards structural tilt along the Tethys oceanic margin. Relatively stable tectonism continued after the Jurassic and was a major factor in the accumulation of the vast reserves of Jurassic sourced oil. Tectonic stability prevented major faulting and structural compartmentalization of the basin features, which provided large areas for hydrocarbon migration as the large and broad anticlines developed into the huge structural traps. The lack of major faulting limited the movement of burial fluids, preserving the early formed porosity and the regionally extensive seals. The present day structures primarily developed from the Late Cretaceous to Miocene as the Tethys Ocean closed.