Long-distance transport of North Gondwana Cambro-Ordovician sandstones : evidence from detrital zircon Hf isotopic composition

A voluminous Early Paleozoic sequence of quartz-rich sandstones was deposited in northern Gondwana following its assembly during the Neoproterozoic-Cambrian Pan-African Orogeny. Field evidence for the sense of transport indicate that sediments were carried from Gondwana hinterland towards the supercontinent margins in the North (present coordinates). Derivation from Pan-African terranes is evident from the ubiquity of detrital zircons with Neoproterozoic U-Pb ages, but the exact provenance of these siliciclastic deposits remains unclear. Herein we present new Hf isotopic data from U-Pb dated detrital zircons of the Cambro-Ordovician sandstone that top the juvenile Neoproterozoic basement of the Arabian-Nubian Shield in Israel and Jordan. Remarkably, the detrital zircon Hf isotopic signal stands in marked contrast with Nd and Hf isotopic signature of the underlying basement. A preponderance (61%) of the Neoproterozoic-aged detrital zircons from the Cambro-Ordovician sandstones in Israel and Jordan yielded negative epsilon (super Hf(t) ) values incompatible with a juvenile source. Therefore, rather than from the adjacent Arabian-Nubian Shield, most of the detrital zircons were derived from distant terrane(s), comprising pre-Neoproterozoic crust reworked during Pan-African orogeny. Because our sampling sites are situated at the northern tip of the Arabian-Nubian Shield, sand must have been transported several thousand kilometers before deposition. This finding also implies that the Arabian-Nubian Shield and other Pan-African orogens of NE Africa were completely warned down by the onset of Cambro-Ordovician deposition and that vast areas in the northern part of Gondwana wer e then low-lying such as to allow transfer of sand across the continent.1 page(s