Keller, M. ; Hinderer, Matthias ; Ajmi, H. al ; Rausch, R.
Hrsg.: Harper, D. A. T. ; McCorry, M. (2009)
Aspects of Ordovician glacial deposits in southern Saudi Arabia.
IGCP 505. Copenhagen (31.08.2009-03.09.2009)
Konferenzveröffentlichung, Bibliographie

Kurzbeschreibung (Abstract)

In southern Saudi Arabia, the Sanamah Formation is of Ordovician or Early Silurian age. Its deposits are mainly found in channels incised into the underlying Cambrian – Ordovician sediments. The channel fill consists of red conglomeratic sandstone with rounded to well-rounded quartz pebbles and cobbles. Repeatedly, large angular clasts of friable, coarse-grained sandstone have been observed in the conglomerates. Above these sediments, there is a succession of light-coloured sandstones, which show almost no internal structure. On outcrop scale, however, it is evident that the sandstones and the conglomerates were deposited in giant foresets comparable to coarse-grained deltas. Above this succession and onlapping the confining borderlands of the valleys are conglomeratic sandstones, badly sorted and with striated clasts. In several sections, striations have been found in the friable sandstones, locally 5 horizons within 40 m of section, that closely resemble glacial striations carved onto hard rock such as basement. We question whether such striations are evidence of direct glacial contact with the sediment. Although there is no doubt that the Sanamah Formation represents a proglacial to periglacial depositional environment, we will discuss the general palaeogeography in which the Sanamah Formation was deposited, why so many features are different from the modern analogues, and why the Sanamah Formation is restricted to broad channels probably draining the Arabian Shield as a hinterland. Finally, we will propose a new model for the generation and preservation of multiple levels of glacial striations in soft sediment.

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