Autochthonous facies and allochthonous debris flows compared: Early oligocene carbonate facies patterns of the Lower Inn Valley (Tyrol, Austria)

Vaziri-Mogaddam

et al. 2017

BSGM

RESUMEN ABSTRACTIn this study, biostratigraphy and paleoecology of the Asmari Formation have been investigated. The study area is located in the Izeh zone, Zagros Basin. Four outcrop sections (Halayjan, Kuh Shur, Kuh-e Bad and Gharibi Ha) have been sampled. Based on distribution of the larger benthic and planktonic foraminifera, five assemblage zones have been recognized. Assemblages 1 and 2 indicate Chattian; assemblage 3 is restricted to Aquitanian and assemblages 4 and 5 suggest Burdigalian. During the Chattian, the carbonate deposits of the Asmari Formation are mostly composed of coralline red algae and large and flat benthic foraminifera. The common components of the Aquitanian are abundant imperforate foraminifera and Favreina asmaricus. The Burdigalian is characterized by coral, coralline algae, and perforate and imperforate foraminifera. During the Burdigalian toward the SE of study area (Gharibi Ha section), the shallow water deposits are abruptly overlain by pelagic limestone. It is interpreted as the result of a regional tilting that started in the upper part of the Burdigalian. The biotic associations suggest that carbonate sedimentation occurred in tropical to subtropical waters under oligotrophic to mesotrophic conditions. The carbonate grain associations in the Asmari Formation suggest heterozoan association. According to paleoecological parameters (such as: nutrient, depth, light and salinity) in the study area, the Asmari Formation belongs to nannofor-foralgal to foramol association which were deposited in slightly hyper to normal saline environment. In the euphotic zone, abundant imperforate foraminifera are present. Basinward, lens shaped rotalids developed in mesophotic conditions, and large lepidocyclinid-nummulitids characterize the sediments of the deeper oligophotic zone.Keywords: Asmari Formation, Oligocene-Miocene, biostratigraphy, paleoecology, larger benthic foraminifera, Zagros Basin.

Section: Burdigaliansupporting

confidence: 69%

Biostratigraphy and paleoecology of the Oligo-Miocene Asmari Formation in the Izeh zone (Zagros Basin, SW Iran)

Vaziri-Mogaddam

et al. 2017

BSGM

“…Vaziri-Moghaddam et al (2006), Corda and Brandano (2003), Nebelsick et al (2001), and Rasser and Nebelsick (2003) considered the similar facies are representative of a shelf lagoon.…”

Section: Discussionmentioning

confidence: 99%

Microfacies and sedimentary environment of the Oligocene sequence (Asmari Formation) in Fars sub-basin, Zagros Mountains, southwest Iran

Sadeghi

Vaziri‐Moghaddam

2010

Facies

The Asmari Formation is a thick carbonate succession of the Oligo-Miocene in Zagros Mountains (southwest Iran). In order to interpret the facies and depositional environment of the Asmari Formation, three measured sections were studied in Fars area for microfacies analyses. There, 12 microfacies types are distinguished based on their depositional textures, petrographic analysis, and fauna. Thus, three major depositional environments were identiWed in the Asmari Formation including open-marine, reef/ shoal, and lagoon. These depositional environments correspond to inner, middle, and outer ramp.

“…The co-occurrence of normal marine (corallinacean and perforate foraminifera) and platform interior (imperforate foraminifera) biota in facies 7 indicates that sedimentation took place in a shelf lagoon and suggests that no effective barrier existed (Romero et al, 2002). A similar facies with imperforated foraminifers, perforated foraminifers and corallinaceans was reported from an inner ramp in the Miocene sediments of the Central Apennines (Corda and Brandano, 2003), and from Early Oligocene deposits of the Lower Inn Valley (Nebelsick et al, 2001). This association, together with the presence of the red algae debris characterizes an inner-shelf depositional setting (Corda and Brandano, 2003).…”

Section: Discussionmentioning

confidence: 83%

Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

Zoeram¹,

Vahidinia²,

Mahboubi³

et al. 2013

Studia UBB Geologia

Abstract. This paper deals with the sequence stratigraphy of the Oligocene (Rupelian-Chattian)-Early Miocene (Burdigalian) Asmari Formation based on microfacies analysis of the sediments in the Ghale Nar Oilfield, central area of Zagros fold-thrust belt. Fourteen facies types typical for upward shallowing trend from open marine (MF 1-3), to shoal (MF 4-5), semi-restricted and restricted lagoon , and finally to near-shore lagoon (MF 13-14) depositional environments were identified. Based on the environmental interpretations, we reconstructed a homoclinal ramp mainly represented by its inner and middle sectors. Facies types MF 4-14 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp influenced by wave-and tide-related processes. MF1 (Pabdeh Formation), and 2-3 with planktonic, large and small hyaline benthic foraminifera represent between fair weather wave base (FWWB) and storm wave base (SWB). Four third-order depositional sequences were recognized. In order to better correlate the identified sequences with those pre-defined of the Asmari Formation in the Dezful Embayment and the Izeh zone that are chronologically well-known, we use their number instead of their name. Sequence 2 mainly consists of an open marine environment in the base, followed by semi-restricted to restricted lagoonal facies. Sequences 36 are characterized by semi-restricted to restricted lagoonal facies. Moreover, the regional relative sea-level change curves correlate well with the global sea-level change curves.