Presentation Title

Petrographic Analysis of the Asilah Sandstone, Morocco

Faculty Mentor

Erik Bender

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

CREVELING 76

Session

POSTER 2

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Several samples of the uppermost Oligocene-early Miocene (Burdigalian) Asilah Sandstone were collected in order to ascertain the sedimentologic history of these rocks. The Asilah Sandstone lies within the westernmost Moroccan Rif Belt. The western Rif of Morocco displays several Tertiary flysch basins deposited in a deep marine setting in the foreland basin and have become involved in the Alpine deformation. The Asilah Sandstone is a decimeter to meter-sized yellowish-brownish turbiditic sandstone deposited at the leading edge of the Tangier thrust sheet. The Asilah Sandstone is interbedded with fine-grained marls and is typical of Mutti’s (1984) type III turbidite packages. Samples collected from the Asilah Sandstones are cross-bedded and are a mix of coarser and finer sand and silt. Petrographic analysis was carried out on thin sections cut from collected samples and reveals their composition to be of the sublitharenite/quartzarenite groups with the omnipresent occurrence of glauconite. Quartz is largely represented by well-rounded monocrystalline grains. Feldspars are very rare and are exclusively represented by single grains of plagioclase. Few lithic clasts are present, mainly consisting of fine-grained sedimentary rock fragments. The lack of polycrystalline quartz varieties and other unstable minerals (e.g., feldspars and lithic fragments), along with low percentages of ultra-stable heavy minerals such as zircon, strongly point to long selective mechanical transport due to successive sedimentary cycles. Samples of interbedded marls appear to be typical deep-water and contain a mix of benthic and planktonic foraminifera in collected samples. Samples appear to be highly laminated and thin section analysis show what appear to be distorted burrows. Petrologically these appear to suggest a deep water setting, possibly under reduced oxygenation. This is consistent with type III turbidite sytems in which deposition takes place in a highstand geological situation, i.e., when sea level covers the continental platform.

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

Petrographic Analysis of the Asilah Sandstone, Morocco

CREVELING 76

Several samples of the uppermost Oligocene-early Miocene (Burdigalian) Asilah Sandstone were collected in order to ascertain the sedimentologic history of these rocks. The Asilah Sandstone lies within the westernmost Moroccan Rif Belt. The western Rif of Morocco displays several Tertiary flysch basins deposited in a deep marine setting in the foreland basin and have become involved in the Alpine deformation. The Asilah Sandstone is a decimeter to meter-sized yellowish-brownish turbiditic sandstone deposited at the leading edge of the Tangier thrust sheet. The Asilah Sandstone is interbedded with fine-grained marls and is typical of Mutti’s (1984) type III turbidite packages. Samples collected from the Asilah Sandstones are cross-bedded and are a mix of coarser and finer sand and silt. Petrographic analysis was carried out on thin sections cut from collected samples and reveals their composition to be of the sublitharenite/quartzarenite groups with the omnipresent occurrence of glauconite. Quartz is largely represented by well-rounded monocrystalline grains. Feldspars are very rare and are exclusively represented by single grains of plagioclase. Few lithic clasts are present, mainly consisting of fine-grained sedimentary rock fragments. The lack of polycrystalline quartz varieties and other unstable minerals (e.g., feldspars and lithic fragments), along with low percentages of ultra-stable heavy minerals such as zircon, strongly point to long selective mechanical transport due to successive sedimentary cycles. Samples of interbedded marls appear to be typical deep-water and contain a mix of benthic and planktonic foraminifera in collected samples. Samples appear to be highly laminated and thin section analysis show what appear to be distorted burrows. Petrologically these appear to suggest a deep water setting, possibly under reduced oxygenation. This is consistent with type III turbidite sytems in which deposition takes place in a highstand geological situation, i.e., when sea level covers the continental platform.