Midra Shale Member Fm

See Dammam Fm

Synonym: Midra and Saila Shales Member; Midra Shale Member

Reference Section:

Made up of attapulgitic shales, generally brown to green (Fig. 2), containing pseudomorphs of pyrite and hematite (Fig. 3), with intercalations of phosphatic discontinuous limestones. It is 16.4 ft. (5m) thick at the reference section (Figs. 1 & 2). It can reach 26.2 ft. (8 metres) on outcrops in the extreme south and disappear in the Northeast. In boreholes, the Midra (and Saila) Shales also exhibits variable thicknesses over the area between Doha and Messaid; some time absent and some other time to around 10m

[Figure 1: Natural exposure at the Reference section locality of the Dammam Formation (Lat. 25°17'3.18"N, Long. 50°48'20.07"E) suggested by Cavelier, Sugden et al. (1975). The Midra (and Saila) Shales, the Dukhan Alveolina Limestone and the bottom portion of the Umm Bab Dolomite and Limestone Members are the only ones that can be observed – Equivalent to letter “E” in the section shown in Fig. 1 in Dammam Fm.]

[Figure 2: Exposure of the Midra (and Saila) Shales at the Reference Locality (Fig. 1). The author is seen measuring the section.]

[Figure 3: Amalgamation of cubic crystals of an iron-rich mineral, probably with a high percentage of pyrite and hematite.]

The member is irregularly fossiliferous. The fauna is variable and include rare branched Bryozoa, indeterminable (Membraniporide?), some Echinoderms (Fig. 8) and Molluscs. Gastropods (Fig. 6) are very few. The ichthyofauna (Figs. 4, 5, 10, 11, 12, 13 and Table 1) is very abundant and was described in detail by Casier (1971) - and discussed by LeBlanc (2008) - who recognized 28 types. The Elasmobranchs are most prevalent with the Lamniformes and Carcharhinides orders. The large Foraminifera (Fig. 7) are sometimes common in the shales (especially Dictyoconoides kohaticus (Davies)) and are usually more abundant in the calcaro-phosphatic intercalations.

The author (LeBlanc, 2008) also found the first ever sirenian Middle Eocene bones from the Arabian Peninsula (Fig. 9). Before this discovery, the closest known localities of sirenians from this time period were in Egypt and India.

[Figure 4: Odontaspis (shark) tooth in its natural position (left) and professionally photographed (right) by the University of Qatar, Environmental Studies Center]

[Figure 5: Various shark teeth from the Midra shale professionally photographed by the University of Qatar, Environmental Studies Center]

[Figure 6: Ferricrete and oxydized gastropods.]

[Figure 7: Nummulites.]

[Figure 8: Echinoderm (sea-urchin) spines]

[Figure 9: Rostral teeth of Pristis fish (or sawfish)]

[Figure 10: Sirenian/Dugong bones: Top left - the Centrum of a cervical vertebra. Top right - First ever sirenian Middle Eocene bone discovered on the Arabian Peninsula (July 6^th 2007 in Qatar). This is a shaft of the 11^th, 12^th or 13^th rib. Bottom: Large rib. All found by the author and interpreted by Dr. Iyad Zalmout.]

[Figure 11: Teeth from Pycnodont fish. They lived from the Middle Cretaceous to the Middle Eocene in calm reef waters and ate hard-shelled molluscs, corals and sea urchins.]

[Figure 12: Stingray tooth plate]

[Figure 13: Shark teeth (and other marine vertebrates) described in detail by Casier (1971). See Table 1.]