wackestoned:My future field assistant using the Hushpuckney Shale as a pillow. I got this sample (th

wackestoned:My future field assistant using the Hushpuckney Shale as a pillow. I got this sample (the shale not the cat) during a week of fieldwork in Kansas/Missouri. During the Late Pennsylvanian Ice Age, the Midcontinent of North America was beneath a tropical, epeiric sea. Cyclothems, repeating series of transgressive and regressive marine to non-marine sediments, recorded glacio-eustatic changes in sea level. This black shale forms the core of a Kansas-style cyclothem, which as sea level rose, typically sequence from a low stand erosional surface, sandstone, transgressive limestone, and gray shale to core black shale. As sea level fell, the black shale grades back into gray shale topped by a regressive limestone and back to sandstone or pelite. The basin scale process formed meter high, continuous beds! The thickness and geometry of the beds hint at basin geometry and timing of ice sheet growth and decay. As a baby, chemistry oriented paleoclimatologist, I was in it for the well preserved carbonate fossils to correlate a modeled sea level curve with oxygen isotope data. My friend and mentor was in it for the oxygen isotopes from PO4 in conodont apatite. My project was a piece of her masters thesis. At the road cuts where we sampled, the limestones were full of low energy environment fossils (eg articulated crinoid stems) to higher energy death assemblages of brachiopods forming a 10 cm layer. -- source link

More pics about