Boundary Between Upper Cretaceous and Lower Paleocene in the Zagros Mountain Ranges of Southwestern Iran

Abstract

In the present study, over 3000 m of Upper Cretaceous sediments (Tarbur Formation) in seven stratigraphic, columnar sections were studied. The area is located in the Zagros mountain ranges of southwestern Iran, attributed to the converging continental Arabian Shield, and is interpreted as the result of subduction and collision. Based on foraminiferal studies of the Tarbur Formation in the sections, we have established many new biozones in the stratigraphic sections. However, investigations of the biozones indicate that there is no lithostratigraphic variation between the Upper Cretaceous and Lower Paleocene sediments in some of the studied sections. The concept of widespread formations and lithologic correlations is not applicable in this area, probably as a result of the tectonic unrest at that time. The biostratigraphic boundary between the Cretaceous and the Lower Paleocene is nevertheless well defined by the intraformational boundary in the sections.

Biostratigraphic Revision of Middle-Cretaceous Biostratigraphy Succession in South Zagros Basin

“…Many geologists have focused upon the carbonate petroleum reservoir rock of the Zagros area because of the well-known oil productivity of this region [1]. One of the most oil producing reservoir rocks of the Zagros basin is the Asmari Formation (Oligo-Miocene) which is well known for petroleum geologists [2].…”

Paleoecology & Paleobiogeography of Orbitoides Genus in Zagros Basin (South West Iran)

“…In Iran this genus have been seen in association with Loftusia, Omphalocyclus, Siderolites and Lepidorbitoides [11,13,14,21]. The morphology (Thin planner shells with lateral chambers) and their association with Siderolites are indication of high energy habitation.…”

“…Current distribution of benthic foraminifrera is between 36° North and 34° South [30]. It seems that the higher migration of foraminifera form equatorial line toward the poles and their geographical distribution is the result of higher temperature at the end Cretaceous comparing to current temperature ( Figure 5 In Lorestan from Sarghach in the surround of Khorramabad [22] and Chamsangar in Southeast of Khorramabad [13,14] and Goavar [22], in High Zagros sub basin from Bolghar mountain in Southwest of Semirom, Ab malakh in south west semirom, Sarab anticline [22], and Ab bagh mountain in Northeast of Lordegan [22], In Fars from Jahrom and Dorodzan dom [31], South East of Kherameh [11,32], Khaneh nahr [33], Sarvestan [34], Chehl Cheshmeh, Chador Mountain in Sachun, Hasan abad in Neyriz and Gadvan Mountain [35], Khaneh Kat, Dariyan and Chehl Cheshmeh [11,36], Gondashtloo, Kuh -e Siah in Sarvestan, Zarghan, Kherameh-1, Kherameh-3, Kherameh-4 [11,21] (Khosro Tehrani and Afghah, 2005, Afghah and Farhoudi, 2012) and Ahmadi well [36] (Table 1). The paleogeography distribution of this genus in Zagros sedimentary basin is between 28̊ 35′ & 34̊ 18′ northern latitude.…”

“…At the North-Eastern margin of this foreland basin, the Tarbur platform was deposited, with its relatively steep platform margins. Rudists, benthic foraminifers (such as Loftusia and Orbitoides) and mollusks (Lopha, oysters, gastropods, bivalves) were the main carbonate producers of the Tarbur platform [9][10][11][12][13]. Skeletal material was partly reworked seawards, and accumulated in outer ramp depositional setting, in association with pelagic fauna.…”

Microbiostratigraphy and Sedimentary Environment of the Sarvak and Kazhdumi Formations in Bahregansar Oil Field

“…Many geologists have focused on the carbonate petroleum reservoirs of the Persian Gulf because of the wellknown oil productivity of this region (Afghah and Farhoudi, 2012). The Sarvak Formation is one of the most significant carbonate reservoirs known to be an oil producer in the Bahregansar oil field (Tabiyejou et al, 2014).…”