GPSW-7 WELL, Sample 69 (Cretaceous of Egypt)

Where: north Western Desert, Egypt (30.0° N, 28.0° E: paleocoordinates 9.8° N, 23.1° E)

• coordinate estimated from map

When: Afropollis jardinus/Cretaceaporites densimurus pollen zone, Bahariya Formation, Early/Lower Cenomanian (99.6 - 93.5 Ma)

• This formation was defined by Said (1962), and El Akkad and Issawi (1963) measured its type section which is located at Gebel El Dist, north of the Bahariya Oasis to be 170 m thick. It is overlain by the Abu Roash Formation and underlain by the Kharita Formation. The age of the Bahariya Formation is Cenomanian (Schlumberger, 1984); Cenomanian (Abdel Kireem and Ibrahim, 1987), based on foraminifera; and late Albian–early Cenomanian (El Beialy, 1994c), and early Cenomanian (Mahmoud and Moawad, 1999), based on palynology. The Bahariya Formation is subdivided into six units, of which unit I (upper pay) and unit IV (lower pay) are potential hydrocarbon-bearing zones based on lithologic and electric log markers (Schlumberger, 1984).

Environment/lithology: shallow subtidal; lithified, gray, calcareous mudstone and lithified, black, gray, calcareous shale

• The sedimentary succession in the GPTSW-7 well starts at the base with the deposition of the Bahariya Formation, in a shallow marine and fluvio-deltaic environment (Schlumberger, 1984). The palynofloras from the early Cenomanian Bahariya Formation are dominated by pteridophytic spores, gymnosperm and angiosperm pollen (Fig. 6) and phytoclasts. Miospores are represented mainly by some smooth forms assigned to Deltoidospora and Triplano- sporites and by sculptured forms such as Cicatricosisporites, among

•others. The high abundance of Crybelosporites suggests a fresh- water environment. The gymnosperm pollen are dominated by Araucariacites, produced by conifer vegetation developed on the relatively dry hinterland associated with ephedroids and Class- opollis/Circulina, both of which are commonly interpreted as derived from xerophytes (Schrank and Mahmoud, 1998). The percentage of marine dinocyst elements (dominant in some samples) is indicated (Fig. 6), and they are dominated by the marginate genus Cyclonephelium, thus indicating coastal to near- shore environment (Eshet et al., 1992; Li and Habib, 1996). The smooth- and thin-walled acritarch Leiosphaeridia is attributable to fresh to brackish water algae (Schrank and Mahmoud, 1998).

•The AOM–Phytoclast–Palynomorph ternary plot of Tyson (1993) (Fig. 5A) as well as the ternary plot of Roncaglia and Kuijpers (2006) (Fig. 5B) suggest that the Bahariya Formation was deposited in a shallow marine to fluvio-deltaic setting with high terrestrial/ fresh-water influx.

• The studied sequence ranges from 1918 to 2170 m (252 m thickness), and is composed of alternating grey calcareous mudstone to grey and black shale with minor sandstone interbeds.

Size class: microfossils

Preservation: soft parts, original sporopollenin

Collection methods: core, chemical

Primary reference: S. El Beialy, H. S. El Atfy, M. S. Zavada, E. M. El Khoriby, and R. H. Abu-Zied. 2010. Palynological, palynofacies, paleoenvironmental and organic geochemical studies on the Upper Cretaceous succession of the GPTSW-7 well, North Western Desert, Egypt. Marine and Petroleum Geology 27:370-385 [C. Jaramillo/G. Doria/G. Doria]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 140447: authorized by Carlos Jaramillo, entered by Gabriela Doria on 09.03.2013

Creative Commons license: CC BY (attribution)

Taxonomic list