HR: 0830h
AN: GP11C-0269    [PDF]
TI: Low Latitude Glaciation in Arabia - A Palaeomagnetic Study of the Neoproterozoic Huqf Supergroup, Oman
AU: * Kilner, B
EM: benk@earth.ox.ac.uk
AF: Department of Earth Sciences, Oxford University, Parks Road, Oxford, OX13PR United Kingdom
AB: The Huqf Supergroup of Oman consists of a sedimentary sequence which was deposited in the Neoproterozoic. Within the Huqf Supergroup there are two distinct glacial packages; the Ghubrah ($\sim$710Ma) and the Fiq ($\sim$600Ma) formations. These have been correlated with the Sturtian and Marinoan glaciations respectively. Higher up in the sequence, part of the Shuram formation ($\sim$560Ma), has been tentatively correlated with the Gaskiers glaciation. In the south of Oman, the Mirbat formation, consisting of siltstones and diamict, is thought to be equivalent in age to the Huqf Supergroup. Samples from 100 sites were demagnetised using either AF or thermal treatment. In all sites a low stability remanence (component A), removed between 0 to400$\deg$C was identified,. It is indistinguishable from present earth field, and is therefore interpreted as a recent VRM. Samples from the middle part of the Huqf; the Fiq diamict and the lower Mirbat formation, have a high stability characteristic component (B). This is removed between 400-585$\deg$C, plat=-51.8$\deg$ and plong=64.9$\deg$. Reversal, folding and conglomerate tests all yield positive results, and the result is therefore interpreted as primary. Samples from the upper Huqf and the upper Mirbat formation, also have a high stability characteristic component (C), distinct from both A and B. It is removed between 400 to $\deg$C, plat=12.9$\deg$, plong=130.1$\deg$. This result yields positive folding and reversal tests and is therefore also interpreted as primary. Two distinct primary components have been identified in both the middle and upper Huqf Supergroup, and in the lower and middle Mirbat formation. This result links the lower Mirbat with the Fiq diamict and therefore the Marinoan glaciation. In the 50My between the deposition of the Fiq and the Shuram formations, Arabia crossed the equator and rotated clockwise. This is the first evidence of Neoproterozoic drift of the Arabian plate prior to collision with Africa. Component C correlates well with similarly aged poles from Africa, suggesting that by 550Ma the African and Arabian plates had collided. Component B from the Fiq diamict has a palaeolatitude of 13$\deg$, a confirmation of massive global cooling during the Marinoan.
DE: 1520 Magnetostratigraphy
DE: 5416 Glaciation
DE: 9619 Precambrian
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting