General setting of the Arabian Intrashelf Basin. Fields sourced from the Arabian Intrashelf Basin Jurassic are coloured green (oil) or red (gas). The main source rock facies (olive brown) defines the extent of the basinal portion. A main premise in this Memoir is that the intrashelf basin is continuous as shown, with a shallow rim. It may have extended further SW in the Rub’ al-Khali (e.g. Hughes et al. 2008), but that area has not been well documented. Palaeolatitudes and the location within the SE palaeotradewind belt are important factors. The northeastern limits of the Late Jurassic Hith Anhydrite seal are shown: it extends south and west to the outcrops, across the Rimthan Arch into the Gotnia–Mesopotamian Basin and into the Rub’ al-Khali. The outcrop in Saudi Arabia was initially a broad synclinal low (Enay et al. 1987) largely filled by end-Callovian deposits. This map is compiled and drawn from information contained in the many sources cited in this Memoir.

Names of oil and gas fields in the region. Fields coloured green and red are sourced from the Arabian Intrashelf Basin. Where the Upper Jurassic anhydrite seals thin and become ineffective in eastern Abu Dhabi, some of the oil and gas in Lower Cretaceous reservoirs is interpreted as sourced from the Jurassic (Yin et al. 2018).

Map showing the trends of some of the published cross-sections used to construct the maps and much of the interpretation in this Memoir. The numbers refer to the figure numbers in this Memoir and to the references in the yellow box. Not all of the sources used are shown in this figure; these are credited where they are used in the figures in other chapters.

Lithostratigraphic nomenclature. The left-hand side shows both the early age dating of the section in Saudi Arabia, which was adopted in other country areas, and the more recent dating in Enay et al. (1987) and Al-Husseini (2009) used in this Memoir. In this Memoir, the main interval of the source rock is interpreted to be a lowstand deposit. Modified Sharland et al. (2001) maximum flooding surfaces are also included on the left-hand side. This chart is repeated in Wilson (2020b, Fig. 3.1, Chapter 3, this Memoir). The intervals in Kuwait have been dated using nannofossils, but comparable data are not known to be available for the interval in Saudi Arabia, hence precise age correlations to Kuwait are not shown in this chart. A general consensus of the correlations is shown in Figure 3.7 in Wilson (2020b, Chapter 3, this Memoir).

Schematic cross-section for the intrashelf basin drawn from the eastern to western rims, illustrating the basic depositional architecture as interpreted in this Memoir. The Dhruma Atash sequence formed a relatively flat platform, above which the intrashelf basin formed in the Tuwaiq sequence. A lowstand restricted the basin and the main source rock interval was deposited. With the subsequent transgression, the Hanifa sequence facies prograded well into the basin, with progradation extending further from the west than from the east. Hanifa deposition ended with a lowstand, marked by subaqueous anhydrite in the basin. The Jubaila-Arab-D sequence(s) largely filled the intrashelf basin. The Arab-D anhydrite filled remaining depositional lows and then blanketed the region. Westward tilt and subsidence began post-Hanifa and continued into the early Tithonian. The Arab-D anhydrite blanketed the region. The Arab-C to Arab-A evaporite–carbonate sequences were formed by transgressions, with evaporite deposition followed by shallow water carbonate deposition. The massive anhydrite interval of the Hith Anhydrite Formation covered the intrashelf basin region. The Jurassic–Cretaceous contact is in the transgressive facies above the Hith Anhydrite Formation.

Jurassic plate tectonic setting of the Arabian Intrashelf Basin (simplified from Torsvik and Cocks 2016). The general setting is on a passive margin of the developing Tethys Ocean after the break-up of Pangea. Tethyan rifting marked by the westwards drift of Gondwana is the main mega-tectonic event affecting the Arabian Intrashelf Basin in its Callovian–Tithonian existence. Its location, exposed to palaeotradewinds and the humid ITCZ, is important (Figs 1.8, 1.9, 1.10).

Van Hinsbergen et al. (2015) have provided an online palaeolatitude calculator using the palaeomagnetic reference frame of Torsvik et al. (2012). This calculator was used to plot the drift during the Toarcian–Tithonian and into the Cretaceous of the reference point located near the north end of the Ghawar field. The position of the reference point stays close to 8° S from the Bathonian through Kimmeridgian, drifts southwards by 2–3° in early Tithonian time and continues to drift southwards into the Cretaceous. Error ranges are shown. The general latitude places the area at the northern portions of the SE palaeotradewind belt and at the margin of latitudes where hurricanes are likely. The palaeolatitude of 10° shown in Figures 1.2 and 1.9 was estimated using this palaeolatitude calculator.

Energy levels around the Arabian Intrashelf Basin on a daily basis were determined largely by the direction of the palaeotradewinds. This map shows where the highest energy levels would be and the likely directions of water flow across the broad Neotethys margin shelf. The Arabian Intrashelf Basin was a huge feature, providing a 1000+ km of wave fetch across the basin, which would drive the water flow towards the Gotnia–Mesopotamian Basin to the north. Greater progradation occurred from the higher energy portions, as indicated for the Hanifa Formation in Figure 1.6. Areas on the sheltered sides generally show both less progradation and thinner intervals in the intrashelf basinal areas, especially for the Hanifa basinal facies.