INVESTIGADORES
VIZAN Haroldo
artículos
Título:
Palaeomagnetism of the Mahatta Humaid Group (Cambrian Early Ordovician, Oman), including a re-interpretation of previous Neoproterozoic palaeomagnetic data
Autor/es:
VIZÁN, HAROLDO; TURNER, PETER; MILLSON, JOHN; IXER, ROB
Revista:
GEOARABIA
Editorial:
GULF PETROLINK
Referencias:
Año: 2009 vol. 14 p. 71 - 96
ISSN:
1025-6059
Resumen:
We carried out a palaeomagnetic study in the Al-Huqf region (Sultanate of Oman)
on rocks that belong to different units of the Cambrian Ordovician Mahatta
Humaid Group. Thirty-nine samples were systematically collected from a
succession ca. 520495 Ma old. Seventeen samples showed characteristic remanent
magnetization components with two antipodal polarities carried by hematite.
Evidence suggests that these components have a primary origin. A detailed
petrographic analysis revealed syntaxial overgrowths parallel to the easy plane of
magnetization of the magnetic carriers that has probably enhanced and reinforced
the primary magnetization. A palaeopole computed with the mean direction of
the 17 characteristic remanent magnetization components was considered
alongside previously published Neoproterozoic early Palaeozoic palaeomagnetic
data, which we placed in an updated chronostratigraphic framework for
the Neoproterozoic Cambrian Huqf Supergroup. Two interpretations were
considered: (1) Oman was detached from the Arabian-Nubian craton until ca. 660
Ma, and it became attached (or was nearby) to it by ca. 630 Ma. In this interpretation,
an apparent polar wander (APW) path of Arabia is proposed between ca. 630
and 500 Ma. The palaeomagnetic directions of Mirbat obtained by Killner et al.
(2005) in rocks 720660 Ma old are therefore assumed as primary, and taking into
account that Oman was an independent block of the Arabian-Nubian craton,
the corresponding palaeopole is not considered in the proposed segment of the
Arabian APW path. (2) The Neoproterozoic data belong to two different tectonic
blocks within the Arabian-Nubian craton and were involved in left-lateral, strikeslip
movements along NW-trending faults. One block included the localities of
Al Jabal al-Akhdar and Al-Huqf and may have rotated counter-clockwise ca.
45° about a vertical axis between ca. 600 and 500 Ma. The other block included
the locality of Mirbat and rotated counter-clockwise ca. 25° about a vertical axis
between ca. 600 and 550 Ma. These suggested block rotations may have played
a role in generating the underlying fabrics for some of the sedimentary basins in
Oman. In the second model, the rocks sampled by Killner et al. (2005) in Mirbat
were re-magnetized during the intrusion of dike swarms at ca. 615600 Ma.