Haushi Gr

The earliest sediments above the ‘Hercynian’ unconformity in Oman are represented by the glacially-influenced sediments of the Al Khlata Fm that form the base of the Haushi Gr. Named after the surface sequences in the northern Al Huqf outcrop area of the Haushi anticline. Column: Oman Subsurface, Oman Outcrop. Hudson and Sudbury (1959) as Haushi Formation, raised to Group status by Winkler (1975) and revised definition by Hughes Clarke (1988). Upward succession of the Al Khaita Fm and Gharif Fm. No subsurface reference sections have been defined for the Group, as Hughes Clarke (1988) only proposed subsurface reference sections at formational level. Safiq South-1 is proposed by Forbes et al. (2010) as a suitable reference section at Group level.

Synonym:

Sandstone. Glacially-influenced of the Al Khlata Fm are conformably overlain by the clastic shallow-marine shifting to alluvial/fluvial sediments of the Gharif Fm. The only carbonates are associated with a marine transgression of the Lower Gharif Member (Haushi Limestone). The clastics in the Haushi Group are characterized throughout by much higher lithic and arkosic content than in the underlying clastics of the Haima Supergroup Gr. "Sequence stratigraphy: For the most part the Haushi Group represents the AP5 Megasequence of Sharland et al. (2001, revised 2004). They place the Upper Gharif clastics in the basal part of their AP6 Megasequence, as representing the initial transgressive unit prior to Khuff carbonate development. … Sharland et al. (2001) place their MFS P10 within Lower Gharif, immediately below the Haushi Limestone. … The pre-Khuff unconformity seen in Saudi Arabia (Al-Husseini, 2008) is taken to mark the Arabia- Cimmeria ‘break up unconformity’, as discussed by Sharland et al. (2001), but this break is not clearly recognized in Oman."

" The Haushi Group can be recognized by the presence of Palynozones 2252 (Hamiapollenites spp.) to 2159 (Anapiculatisporites concinnus, redefined as Punctatisporites spp.). More than any other part of the column the Haushi Group has been subject to extensive biostratigraphic, in this case palynological, study reflecting the economic importance of these sediments as primary oil reservoirs. This is particularly so for the Al Khlata Fm, where palynological content often provides the only differentiating criteria when dealing with the complex geometries and extreme lateral variation seen in these glaciogenic rock units. Key age calibration points have been provided by plant, fusulinid and brachiopod megafossil recovery. Broutin et al. (1995), Berthelin et al. (2003) and Berthelin et al. (2006) describe a rich and varied plant assemblage from the very top of the Upper Gharif in the northern Al Huqf outcrop region. This ‘Gharif Paleoflora’ has been interpreted to be of late Roadian – early Wordian in age. Angiolini et al. (2006) indicate a Sakmarian age for the Haushi Limestone based on fusulinid recovery with supporting brachiopod evidence. … Osterloff et al. (2004b) also believe that the Al Khlata could range down to a Namurian equivalent age by comparison with European assemblages (i.e. ca. Bashkirian). This uncertainty arises from the need to ‘jump’ correlate these non-marine sequences to comparable spore and pollen recovery associated with marine fauna in Western Australia, which only then in turn can be compared to the marine fauna in the type Russian Carboniferous. As applied in Penney et al. (2008), the glaciogenic nature of the Al Khlata sediments, with multiple reworking episodes, dictates the need for a particular quantitative based approach when dealing with the palynological content. Detailed age definitions can only be tentative within a general late Carboniferous – early Permian range. Correlation with sequences in Saudi Arabia is provided by comparison with the OSPZ6 to OSPZ1 palynological zones of Stephenson et al. (2003) (see also Stephenson, 2004). These are further documented in Osterloff et al. (2004b) and Stephenson (2006) for the Gharif Fm and Penney et al. (2008) for the Al Khlata Fm."

"Following the widespread ‘Hercynian’ uplift and erosion in the Carboniferous (Konert et al., 2001; Al-Husseini, 2004b; Faqira et al., 2009) the northern Gondwanan terranes rifted with the opening of the Neo-Tethys Ocean in the latest Carboniferous – earliest Permian (Konert et al., 2001). The earliest sediments above the ‘Hercynian’ unconformity in Oman are represented by the glacially-influenced sediments (glaciolacustrine, glaciodeltaic and glaciofluvial settings) of the Al Khlata Fm that form the base of the Haushi Group. Paleogeographic reconstructions show that the Arabian Peninsula at that time was situated close to the South Pole, at high latitudes above some 40–45°S. Clastic sediments of the Gharif Fm conformably overlie the Al Khlata Fm, deposited in the subsequent deglaciation period with the Arabian Plate rapidly moving some 20° northwards to middle latitudes. Following an initial marine transgression these Gharif Fm sediments are dominated by fluvial/ alluvial clastics deposited under progressively dryer conditions, from cold, through temperate to arid and ultimately a wetter, tropical seasonal climate. During Gharif times Oman was situated on the eastern flank of the Rub’ Al-Khali Basin, an intra- continental basin at the edge of Neo-Tethys, with a limited sediment source area from the Al Huqf High to the east. In late Gharif times there is a notable increase in the clastic supply from the east, probably in response to uplift in the source areas along the shoulders of the Neo-Tethys rifting system."

The stratigraphy of the Haushi Group was reviewed by Osterloff et al. (2004a, b) as part of a regional Carboniferous to Early Triassic review (Al-Husseini, 2004a).