Applications of nummulitids and other larger benthic foraminifera in depositional environment and sequence stratigraphy: an example from the Eocene deposits in Zagros Basin, SW Iran

Abstract

The Tale-Zang Formation in Zagros Mountains (south-west Iran) is a Lower to Middle Eocene carbonate sequence. Carbonate sequences of the Tale-Zang Formation consist mainly of large benthic foraminifera (e.g. Nummulites and Alveolina), along with other skeletal and non-skeletal components. Water depth during deposition of the formation was determined based on the variation and types of benthic foraminifera, and other components in diVerent facies. Microfacies analysis led to the recognition of ten microfacies that are related to four facies belts such as tidal Xat, lagoon, shoal and open marine. An absence of turbidite deposits, reefal facies, gradual facies changes and widespread tidal Xat deposits indicate that the Tale-Zang Formation was deposited in a carbonate ramp environment. Due to the great diversity and abundance of larger benthic foraminifera, this carbonate ramp is referred to as a "foraminifera-dominated carbonate ramp system". Based on the Weld observations, microfacies analysis and sequence stratigraphic studies, three third-order sequences in the Langar type section and one third-order sequence in the Kialo section were identiWed. These depositional sequences have been separated by both type-1 and type-2 sequence boundaries. The transgressive systems tracts of sequences show a gradual upward increase in perforate foraminifera, whereas the highstand systems tracts of sequences contain predominantly imperforate foraminifera.

Microfacies analysis and paleoenviornmental interpretation of the Qom Formation, South of the Kashan, Central Iran

“…Lack of rotaliines and high abundance but low diversity of miliolids and alveolinids may be indicative of hypersaline Carbonates Evaporites (2011) 26:255-271 259 conditions, a typical of lagoonal setting. The presence of mud matrix in this microfacies shows that, for the most part, deposition took place in a low to moderate energy environment (Adabi et al 2008). Based on Sadeghi et al (2009) miliolids-dominate benthic foraminifer assemblages reflect decreased circulation and probably reduced oxygen contents or euryhaline conditions, as well as, Allahkarampour Dill et al (2010) believed that, the prevalence of porcelaneous foraminifera strongly suggests deposition in a protected inner shelf environment.…”

Tectonically driven carbonate ramp evolution at the southern Tethyan shelf: the Lower Eocene succession of the Galala Mountains, Egypt

“…Geel 2000). The coeval occurrence of large-Xat nummulitids and alveolinids, reXecting two diVerent environments either point to an oVshore transport of alveolinids (Adabi et al 2008) or to a shoal-to-inner ramp transport of nummulitids.…”

“…Luterbacher 1984;Kuss 1986;Rasser 1994;Wielandt 1996;Pujalte et al 1999;Scheibner et al 2001a;Cosovic et al 2004;Özgen-Erdem et al 2005;Rasser et al 2005;Adabi et al 2008), shallowbenthic biostratigraphy (e.g. Schaub 1992;Serra-Kiel et al 1998;Scheibner and Speijer 2009), oil potential (e.g.…”

Multispiral growth in Nummulites

“…Since the studies by Hottinger (1982Hottinger ( , 1983 and Hallock (1985), larger foraminifera have been considered as extreme K-strategists adapted to a stable, oligotrophic environment (Hallock, 1988;Brasier, 1995;McGowran and Li, 2000;Scheibner et al, 2005;Adabi et al, 2008;BouDagher-Fadel, 2008;Scheibner and Speijer, 2008).…”