Izhara Fm

Q.P.C. Well Kharaib No. 1, lat 25°27’09” N, long. 51°11’56” E, elevation 41.5 m (136 ft), completed 29.6.1953, between drilled depths 2317 and 2454 m (7600 and 8052 ft).

The formation takes its name from a locality near the type section. W. Sugden (unpublished report)

Synonym: “Lower Dhruma Formation”, Powers, 1968. “Izhara formation”, Dominguez, 1965.

Reference Section:

Top. 1. Limestone, grey, porous, with scattered dolomite crystals. 24.4 m (80 ft). 2. Limestone, grey to dark grey, fine grained, dense, with streaks containing pellets, often pyrite-stained, sometimes argillaceous, silty. Lowest part variably dolomitic and including beds of dark grey marl and shale. 56 m (185 ft). 3. Limestone, grey, fine-grained, dense in part, very dolomitic. 6 m (20 ft). 4. Dolomite, grey to grey-brown, calcareous, dense at top, becoming porous, saccharoidal. 10.6 m (35 ft). 5. Limestone and dolomite, grey, fine-grained, dense, with argillaceous beds in upper and lower parts. 40 m (132 ft). Base. Its thickness is 137 m (452 ft).

The type description is a modification of the original account written after the formation had been penetrated for the first time. It emphasizes the presence of a 24 m (80 ft) upper member composed of porous, pure carbonate, predominantly pellet and lump packstones and grainstones with interbedded lime mudstones, which contrast strongly with the impure, variably developed limestone of the overlying Araej Formation and the underlying Lower Izhara.

The lower part of the Izhara Formation is composed of interbedded pellet grainstones, argillaceous packstones and lime mudstones, dolomite and shale. These contain increasing quantities of quartz sand towards the base. Thin, discrete sandstone bodies have been recorded in the lower part.

In 1. Rare Nautiloculina oolithica Mohler, Glomospira sp., Paleotrix sp. In 2. Haurania sp.

This unit contains a characteristic microfauna including Haurania spp. and forms related to Cockinolinopsis and Orbitopsella.