L04_Holocene Sands_Key - boundaries within the...

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Lab 4: Holocene Sands (Key): 1) ZQD a) Bimodal subrounded/rounded/well-rounded (larger grains) and some angular (smaller grains) b) second cycle (due to bimodal rounding) 2) ZCL a) coated b) hematite or goethite c) subrounded to well-rounded (few sub-angular) 3) XRP a) not all beach sands are well-rounded and well-sorted – this one is poorly sorted and the grains are angular/subangular to subrounded. b) coarse grains are more rounded (more mass more energy upon impact to round) – finer grains are too small to make an impact, but also maybe two different source areas. 4) XPS a) not all beach sands are well-rounded and well-sorted – this one is moderately sorted and the grains are angular/subangular to subrounded. 5) XLA *Note plag laths and dark matrix* 6) XIV a) chert softer than quartz because it is more brittle than quartz and breaks along the many grain
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Unformatted text preview: boundaries within the polycrystalline, microncrystalline rock while a monocrystaline quartz grain can only break with fracture (takes more energy). Also, breakage following the irregular grain boundaries in chert results in an angular grain. OR chert has a local source and is less abraded 7) XXL a) Rock fragments are very well rounded, quartz is subrounded b) California coast most effective (3 vs 4) 8) ZEV a) Very well to well-sorted b) subrounded 9) XTE a) subrounded to rounded (some subangular to angular) b) fairly immature - hundreds of km 10) AI-88-105 a) well to very well within laminae, but overall moderate sorting (some places poor) 1...
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This note was uploaded on 01/27/2011 for the course GEO 416M taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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