Influence of paleo-Trade Winds on facies patterns of the Cambrian Shanganning Carbonate Platform, North China

The Shanganning Carbonate Platform (SCP) of the North China Craton (NCC) was located in the Trade Winds belt during the Cambrian, which influenced its facies development. In recent years, numerous drillcores have been recovered from these units, but the depositional environments and facies architecture of this large (similar to 2.0 x 10(5) km(2)) carbonate platform system have not yet been reported in detail. In this study, we integrate sedimentological and magnetic fabric data collected from outcrops and drillcores in order to document variation in microfacies and facies associations within the SCP, to infer paleowind directions and constrain the paleogeographic location of the SCP, and to evaluate eolian controls on platform development. This analysis documented numerous carbonate microfacies belonging to six fabric types (mudstone, wackestone, packstone, grainstone, framestone, and dolostone) along with rarer siliciclastic sediments. These microfacies belong to facies associations representing tidal flat, open platform, platform margin, slope, and deep basinal depositional environments. Anisotropy of magnetic susceptibility (AMS) measurements yielded mean paleocurrent directions for the Early, Middle, and Late Cambrian of 114 degrees, 63 degrees, and 83 degrees (+/- similar to 30 degrees) from paleo-north, respectively, that were relatively consistent for 12 out of 13 platform-margin sites, all vectors being corrected for a post-Cambrian similar to 150 degrees clockwise rotation of the NCC. These wind orientations are consistent with the SCP shifting from south of the paleo-Equator in the Early Cambrian to north of it by the Middle Cambrian. Paleo-Trade Winds influenced facies patterns across the platform, producing a distinct windward-leeward zonation. The windward margin is characterized by well-sorted oolitic grainstone, as well as (favositids) coral and (dasycladacean) algal-sponge framestone, and the leeward margin by poorly-sorted oolitic wackestone-grainstone and fine bioclastic sediments. The present study is innovative in 1) integrating microfacies and AMS analyses in order to establish paleowind patterns and influences on an ancient carbonate platform, 2) documenting windward-leeward variation in quantifiable sediment properties across the SCP, and 3) constraining the paleo-hemispheric location of the NCC during the Cambrian.