Eolian-derived siltstone in the Upper Permian Phosphoria Formation: Implications for marine upwelling

摘要: Previously described organic-rich shale facies of the Meade Peak Member Phosphoria Formation at Soda Springs, Idaho, consist well-sorted, laminated siltstone containing little or no clay. The planar-parallel fabric preserved in many beds suggests suspension settling onto outer shelf upper slope, most likely under low oxygen conditions. Evidence for transport silt to depositional site by sediment gravity flows is absent, as are sandstone beds. We propose that record subaqueous deposition windborne was transported southward from central Montana. As such, they provide first direct geologic evidence a wind regime favorable marine upwelling, process commonly postulated have localized Permian phosphatic sediments. They may also indirect upwind eolian sand time.