134 



A.W.A. RUSHTON AND J.H. POWELL 



SAUDI ARABIA 



Outcrop of Burj Formation and 

 Khusheiba Sandstone Fm. 

 (shown stippled) 



\ Lithofacies boundaries 

 i during deposition of 

 \ Numayri Dolomite 



Borehole location showing 

 thickness (m) of Burj Fm. 



100 km 



Fig. 2 Sketch-map showing the outcrop of the Burj Formation in Jordan and the position of localities mentioned in the text. Lithofacies boundaries 



obtaining during deposition of the Numayri Dolomite are shown for southern Jordan. Degrees of latitude and longitude are shown at the edge of the map. 

 Selected boreholes: GTZ-2D = Geothermal Zarqa Main-2D. NH-1 = Northern Highland 1. SA-1 = Safra 1. SW-1 = Suweileh 1. WS-3 = Wadi Sirhan 3. 

 An asterisk indicates the minimum thickness of the Burj Formation in boreholes where the Hanneh Siltstone was not recognised and the top of the 

 formation was taken at the top of the Numayri Dolomite Member (sensti Andrews, 199 1 ). 



Zarqa Ma'in outcrop. The outcrop 1 km north of Wadi Zarqa 

 Ma'in (Fig. 2) is incomplete as only the upper part of the formation 

 is exposed (Fig. 6). The succession probably belongs to the upper- 

 most part of the Numayri Dolomite Member and/or the Hanneh 

 Siltstone Member. At this locality about 3 m of grey finely lami- 

 nated, fine-grained quartz arenite with burrows and ripple 

 cross-lamination, at the base, are overlain by intercalated green- 

 grey, cross-laminated siltstone, fine-grained sandstone and shelly 

 grainstone, passing up to oolitic packstone and cross-bedded trilo- 

 bite grainstone (4 m). The eroded top of the latter is overlain by 

 marine siliciclastic rocks with bimodal cross-bedding, trilobite traces 

 and Harlania burrows (24.5 m). A second carbonate unit (3 m) 

 follows above, consisting of trilobite, brachiopod, hyolithid 

 grainstones, oolitic and cross-bedded in part, and this in turn is 

 overlain by about 50 m of marine siliciclastic strata. These consist of 

 fine- to medium-grained bimodal trough cross-bedded sandstones 

 with small dune forms, intercalated with parallel laminated, ripple 

 cross-laminated, green to mauve, micaceous siltstone and fine- 

 grained sandstone with oscillation and interference ripples. Sparse 

 surface traces and burrows are present in the fine-grained litho- 

 logies. 



ENVIRONMENT OF DEPOSITION 



Early workers (Hull 1886; Blanckenhorn 1914) recognised the 

 marine nature of the formation by the presence of brachiopods, 

 trilobites and hyoliths in the carbonates; subsequently, marine cal- 

 careous algae, including Gin<anella sp., were identified by J. H. 

 Powell in thin sections of the oncolite lithofacies. The siliciclastic 

 strata contain an ichnofauna characteristic of shallow-water envi- 

 ronments, including the arthropod resting and crawling traces 

 Ritsophycus and Cruziana, which are common on some of the 

 bedding planes in the Tayan Siltstone and Hanneh Siltstone mem- 

 bers, and sub-vertical burrows, including Skolithos. Amireh et al. 

 (1994) also identified Diplocraterion and Tigillites from the Hanneh 

 Siltstone at Wadi Numayri. and Cruziana aegyptica Seilacher ( 1 990), 

 Diplocraterion sp. and Scolecia sp. from siliciclastic rocks at Wadi 

 Quseib. 



From the base upwards, a clear pattern of marine transgression 

 and regression is indicated by the fauna and sedimentary structures 

 in the Wadi Numayri type area (Powell 1988, 1989; Amireh et al.. 

 1994). The Tayan Siltstone overlies medium-grained sandstones 



