Tectonic and Subsidence Controls on Jurassic and Triassic Stratigraphy and Depositional Patterns of the Arabian Plate

摘要

The margins of the Arabian Plate evolved as passive and passive-transform margins of the Tethys Ocean during the Triassic and Jurassic. Regional upwarps are recorded as plate- wide unconformities with variable amounts and distributions of erosion. Subsequent thermal-tectonic subsidence created accommodation space, allowing onlap onto unconformities and preservation of eustatically-driven sequences. The Jurassic and Triassic section consists of 14 second-order sequence sets, each with 2 to 6 third-order sequences typified by transgressive-to-highstand shoaling-upward systems tracts (Figure 1). Third-order sequence boundaries show little erosion or onlap. The Lower and Middle Triassic are characterized plate-wide by carbonates (Figure 2). The Upper Triassic is shallow- marine and non-marine (Minjur) clastics on the southern Arabian Plate (SAP) and more continuous carbonate-evaporite deposits on the northern Arabian Plate (NAP). An unconformity below the Minjur cuts into the carbonates across the NAP and the Qatar arch. Another unconformity erodes the Minjur, and together these two unconformities cut through the Triassic on the southern margin of the SAP. These unconformities are related to uplift when India started to rift away from Arabia. Liassic deposition started in the NAP and progressively lapped onto Triassic rocks from the north, covering the Qatar Arch last during the Toarcian (Figure 3). The Gotnia Basin, a starved basin with thin deep-water sediments, formed in the NAP in the Middle Jurassic. The Gotnia Basin was rimmed by oolitic carbonates, as was a zone which extended to the SW along the present-day Arabian Gulf. These shoals formed a barrier SW of which were platform-interior carbonates, in some cases organic-rich. The paleogeography changed in thE Kimmeridgian, when evaporites filled the Gotnia Basin and intercalated carbonates and evaporites of the Arab and Hith Formations covered the SAP. An unconformity occurred in the Tithonian, with deep erosion regionally in southeastern Arabia and on isolated salt structures across the SAP.