18 research outputs found
The present and future of QCD
This White Paper presents an overview of the current status and future perspective of QCD research, based on the community inputs and scientific conclusions from the 2022 Hot and Cold QCD Town Meeting. We present the progress made in the last decade toward a deep understanding of both the fundamental structure of the sub-atomic matter of nucleon and nucleus in cold QCD, and the hot QCD matter in heavy ion collisions. We identify key questions of QCD research and plausible paths to obtaining answers to those questions in the near future, hence defining priorities of our research over the coming decades
Characterization of hardâtoâdifferentiate dune stratification types in the Permian Coconino Sandstone (Arizona, USA)
Dune stratification types, which include grainfall, grainflow and ripple lamination, provide a record of the fineâscale processes that deposited sediment on palaeoâdune foresets. While these facies are relatively easy to distinguish in some crossâbedded sandstones, for others â like the Permian Coconino Sandstone of northern and central Arizona â discrete stratification styles are hard to recognize at the bedding scale. Furthermore, few attempts have been made to classify fineâscale processes in this sandstone, despite its renown as a classic aeolian dune deposit and Grand Canyon formation. To interpret depositional processes in the Coconino Sandstone, crossâbed facies were characterized using a suite of sedimentary textures and structures. Bedding parameters were described at multiple scales via a combination of field and laboratory methods, including annotated outcrop photomosaics, strike and dip measurements, sandstone disaggregation and laserâdiffraction particle analysis, highâresolution scans of thin sections, and scanning electron microscopy. Crossâbeds were observed to be laterally extensive alongâstrike, with most dip angles ranging from the midâteens to midâtwenties. While some crossâbed sets are statistically coarser near their bases, others exhibit no significant vertical sorting trends. Both massive and laminated textures are visible in highâresolution scans of thin sections, but laminae contacts are commonly indistinct, making normal and reverse grading difficult to define. Diagenetic features, such as stylolite seams and large pores, are also present in some samples and might indicate alteration of original textures like detrital clay laminae and carbonate minerals. Observed textures and sedimentary structures suggest that the crossâbeds may consist of grainflow and grainfall deposits, but these remain difficult to differentiate at outcrop and thinâsection scales. This characterization of fineâscale processes will play a critical part in the development of depositional models for the Coconino Sandstone and elucidate interpretations for similar crossâbedded formations