caa a22 4500 386402442 CHVBK 20180307112205.0 cr unu---uuuuu 161130e198905 xx s 000 0 eng 10.1017/S0016756800022366 doi S0016756800022366 pii (NATIONALLICENCE)cambridge-10.1017/S0016756800022366 Schieber J. Department of Geology, The University of Texas at Arlington, Arlington, Texas 76019, U.S.A. The origin of the Neihart Quartzite, a basal deposit of the Mid-Proterozoic Belt Supergroup, Montana, U.S.A [Elektronische Daten] [J. Schieber] The Neihart Quartzite is the basal quartz arenite unit (≍270m thick) of the Mid-Proterozoic Belt Supergroup of western North America. Petrographic studies indicate a source area with plutonic granitic, metamorphic and felsic volcanic rocks. Extreme textural maturity and bimodality indicate an episode of aeolian transport for the detrital quartz grains. The lower 80% of the Neihart Quartzite were probably deposited by braided streams, whereas the upper 20% were deposited in shoreline environments. Residual material that was ‘stored up' on the pre-Beltian cratonic surface and underwent aeolian reworking was the likely source material for most of the Neihart Quartzite. Less mature sediments in the top portion of the Neihart Quartzite indicate uplift and erosion of new source material during Neihart deposition. Other known cratonic quartz arenites, such as the St. Peter Sandstone (Ordovician), Lamotte Sandstone (Cambrian) and Flathead Quartzite (Cambrian), are thin (tens of metres thickness) and exhibit sheet-like geometry. In contrast, the Neihart Quartzite and its probable lateral equivalents are considerably thicker and increase in thickness towards the central portions of the basin. It thus appears that Belt sedimentation began with accumulation of a basal quartz arenite unit, and that sand for that unit was transported by braided streams from the surrounding craton to a gradually subsiding Belt basin. Copyright © Cambridge University Press 1989 Geological Magazine Cambridge University Press 126/3(1989-05), 271-281 0016-7568 126:3<271 1989 126 GEO https://doi.org/10.1017/S0016756800022366 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0016756800022366 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Schieber J. Department of Geology, The University of Texas at Arlington, Arlington, Texas 76019, U.S.A NATIONALLICENCE 773 0- Geological Magazine Cambridge University Press 126/3(1989-05), 271-281 0016-7568 126:3<271 1989 126 GEO CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge