Lisan Gr
Type Locality and Naming
The Lisan Group is a fluvial succession deposited during the opening of the Gulf of Aqaba in the early Pliocene. The Lisan formation (here Lisan Gr) was named by Clark (1986) to replace the term ‘Ifal Fm of Bokhari (1981). The Lisan formation is upgraded to group status in this nomenclature to acknowledge the upgrading to formational status of the previous member status of the Ifal and Badr units. It consists of two discrete lithologies: (1) a siliciclastic succession, assigned here to the Ifal Fm; and (2) a carbonate lithology assigned here to the Badr Fm. The type section of the Lisan Group is located at the western edge of the Ifal Plain (Clark, 1986). In the subsurface, the Lisan Group is defined in the Auxerap/Tenneco exploration well Yuba-1 between 2,541–4,011 ft, onshore coastal Saudi Arabian Red Sea.
Column: Red Sea Saudi Arabia.
Synonym: Ifal Fm, Lisan Fm
Lithology and Thickness
"The Lisan Group consists of carbonates and rhythmic, alternations of poorly consolidated, fluviatile sandstones and conglomerates. Clark (1986) described thin, concentric beds of gypsum that emerge from the Ifal Plain as ridges that may represent part of the general Ghawwas-Lisan Quaternary succession. These features may be due to the deep-seated diapiric movement of evaporites. In the Midyan subsurface, the Lisan Group consists of coarse- and fine-grained siliciclastics and carbonates. . . . The Lisan Group ranges in thickness from 1,470 ft (448.2 m) in the reference well to in excess of 4,500 ft (1,372 m) in wells drilled in the Al Wajh Basin." (Hughes and Johnson, 2005)
Relationships and Distribution
Lower contact
" In the type section, the Lisan Group unconformably overlies the Ghawwas Fm.. the base of the Lisan Gr is difficult to pick with certainty from electric logs because the clastics of the Ghawwas Fm sometime grade into the Ifal Fm. Clark (1986) described an unconformity between the Lisan Gr and the Mansiyah Fm on the east side of Jabal Rughama." (Hughes et al., 1999)
Upper contact
Present surface
Regional extent
The Lisan Group crops out on the eastern margin of Jabal Rughama underlying much of the Ifal Plain. It is distributed widely along the Saudi Arabian Red Sea in both the surface and subsurface.. The Lisan Group is equivalent to the Wardan Fm (siliciclastic) and Shukheir Fm (carbonate) of the Gulf of Suez, and the Abu Shagara Fm of Sudan (Carella and Scarpa, 1962; Sestini, 1965; Hughes and Beydoun, 1992). The Lisan Gr is also equivalent to the open-marine syn-rift tectono-sedimentary unit D of Plaziat et al. (1990).
GeoJSON
Fossils
"Planktonic Zone N21 (Late Pliocene) based on the first downhole occurrence of Globigerinoides extremus; Nannofossil Zone NN17 (Late Pliocene) based on the first downhole occurrence of Dicoaster pentaradiatus; Nannofossil Zone ?NN16–15 (Late to Early Pliocene) based on the first downhole occurrence of Reticulofenestra pseudoumbilica and of Sphenolithus moriformis. The ‘clastic’ Ifal Fm unit is typically near-barren of both palynmorphs and kerogen. The ‘carbonate’ Badr Fm unit has yielded sparse dinocyst assemblages typified by Tuberculodinium vancampoae." (Hughes and Johnson, 2005)
Age
Depositional setting
" In outcrop, the formation consists mostly of fluviatile and delta-plain deposits. Along the southern flank of Jabal Kibrit, gypsum beds and limestones contain echinoids and bivalves that indicate shallow-marine depositional conditions. Subsurface indications are of sedimentary environments ranging from supratidal, through intertidal and shallow-marine carbonate to upper bathyal, based on the variable character of the foraminiferal populations." (Hugest et al., 1999)
Additional Information