Um Zariq formation, southeast sinai, Egypt: A new record of the Sturtian Snowball Earth event in the Arabian Nubian Shield

Abstract

Despite the vast extent of the Arabian Nubian Shield (ANS) and its growth during the renowned Neoproterzoic dramatic climatic changes (Snowball Earth Events), only few records of snowball events are identified among its rocks. Here we present geological and geochemical evidence that the northern part of the Arabian Nubian Shield (Um Zariq Formation (UZF), southeast Sinai, Egypt) witnessed global snowball event(s). The UZF was deposited in a convergent plate margin during Cryogenian and comprises metapelitic schists and cap-carbonates on top. The whole succession underwent amphibolite facies metamorphism around 660 Ma ago. In the upper most part of the metapelitic schists, intercalations of conglomeritic, poorly sorted components and large pebbles show many features comparable to metamorphosed diamictites and dropstones. The arsenic (As) contents of metapelites are 1–3 orders of magnitude higher than average phyllites. The high As contents and the presence, cap carbonates, diamictites and dropstones at UZF point toward deposition under glacial -postglacial conditions apparently during the Sturtian (717-660 Ma) snowball event.