TY - JOUR

T1 - Age, microfacies and depositional environment of the Middle to Late Paleocene shallow-marine carbonates in the Sirt Basin of Libya (Upper Sabil Formation): „Are Intisar domal structures pinnacle reefs?”

AU - Vrsic, Ales

AU - Gawlick, Hans-Jürgen

AU - Schlagintweit, Felix

AU - Machaniec, Elzbieta

AU - Gharsalla, Mohamed

N1 - Publisher Copyright: © 2021, The Author(s).

PY - 2021/10

Y1 - 2021/10

N2 - In the central-eastern Sirt Basin, enigmatic Intisar domal structures host significant hydrocarbon accumulations. These structures have been commonly interpreted as pinnacle reefs/bioherms occurring in the open-marine basinal environment. Generally, pinnacle reefs/bioherms are mainly characterized by in situ carbonates. The current study challenges the Intisar pinnacle reef/bioherm model by examining one of the domal structures in terms of biostratigraphy, microfacies and depositional environment. These structures were dated using larger benthic foraminifera, which yielded a Middle to Late Paleocene age (Selandian–Early Thanetian). Thirteen microfacies types representing different carbonate ramp environments ranging from outer ramp to inner ramp, were defined. Outer ramp deposits have been observed adjacent to the domal structure, represented mainly by wackestone with small benthic and planktonic foraminifera. The outer ramp deposits are most likely isochronous to the domal structures. The lower part of the domal structures is composed mainly of foraminiferal–algal–echinodermal packstones. The upper part is characterized by foraminiferal–algal–echinodermal packstones with intercalated microbialite–coral boundstones. The euphotic inner ramp deposits are preserved on the crest of the domal structure, consisting of grainstone and packstone rich in Glomalveolina. As a result of this study, the Intisar domal structures are seen as erosional relics of a carbonate ramp and no evidence for pinnacle reef/bioherm model was found.

AB - In the central-eastern Sirt Basin, enigmatic Intisar domal structures host significant hydrocarbon accumulations. These structures have been commonly interpreted as pinnacle reefs/bioherms occurring in the open-marine basinal environment. Generally, pinnacle reefs/bioherms are mainly characterized by in situ carbonates. The current study challenges the Intisar pinnacle reef/bioherm model by examining one of the domal structures in terms of biostratigraphy, microfacies and depositional environment. These structures were dated using larger benthic foraminifera, which yielded a Middle to Late Paleocene age (Selandian–Early Thanetian). Thirteen microfacies types representing different carbonate ramp environments ranging from outer ramp to inner ramp, were defined. Outer ramp deposits have been observed adjacent to the domal structure, represented mainly by wackestone with small benthic and planktonic foraminifera. The outer ramp deposits are most likely isochronous to the domal structures. The lower part of the domal structures is composed mainly of foraminiferal–algal–echinodermal packstones. The upper part is characterized by foraminiferal–algal–echinodermal packstones with intercalated microbialite–coral boundstones. The euphotic inner ramp deposits are preserved on the crest of the domal structure, consisting of grainstone and packstone rich in Glomalveolina. As a result of this study, the Intisar domal structures are seen as erosional relics of a carbonate ramp and no evidence for pinnacle reef/bioherm model was found.

KW - North Africa

KW - Paleogen

KW - Stratigraphy

KW - Sedimentology

KW - reservoirs

KW - Biostratigraphy

KW - Depositional geometry

KW - Larger benthic foraminifera

KW - Microfacies analysis

KW - Western Tethys

UR - http://www.scopus.com/inward/record.url?scp=85113741607&partnerID=8YFLogxK

U2 - 10.1007/s10347-021-00635-y

DO - 10.1007/s10347-021-00635-y

M3 - Article

VL - 67

JO - Facies

JF - Facies

SN - 0172-9179

IS - 4

M1 - 27

ER -