Geol 101 Sedimentary rocks cont

Geol 101 Sedimentary rocks cont - Coal o Plant remains...

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Geol 101 Sediments Continued 08/11/2007 14:16:00 How sediment becomes rock Diagenesis: o Chemical, physical, and biological changes that affect sediment from  deposition to lithification o Very low temperature, low pressure metamorphism o Processes Compaction Cementation (carbonate, silica, iron oxides) Recrystalization of less stable minerals. Argonite -> calcite(polymorphs) Chemical alteration Slow decay of organic matter -> peat Clasitc Sedimentary Rocks Classified on size of lithified grains: o Conglomerate (gravel) o Sandstone o Siltstone o Mudstone (clay) Chemical Sedimentary Rocks Lithification of chemical precipitates o Evaporate deposits o Banded iron formations o Phosphorus deposits o Chert (fine grained, interlocking quartz crystals) Biogenic Sedimentary Rocks Limestone (calcite): most abundant
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o Coquina: coarse grained shell debris o Reef Limestone: cemented reef organisms o Chalk: compacted minute carbonate shells
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Unformatted text preview: Coal o Plant remains accumulate in swamps o From peat (60% C) o Peat is compressed (water loss/CH4 generation) o Converted to lignite o Coal Oil Shale o Organic-rich clastic rock o Dead organisms buried in marine or lake muds contain organic oils and fats o With burial, wax-like substances are formed (oil shale) o When heated produces hydrocarbons Environmental Clues Sedimentary rocks reflect their environment of formation (rounding). Bedding planes o Ripple Marks o Footprints, trails, and raindrop impressions Fossils o Some animals and plants are restricted to certain climates Color o Dark colors: iron sulfides and organic detritus low oxygen o Red/Brownish colors : iron oxides plenty of oxygen 08/11/2007 14:16:00 08/11/2007 14:16:00...
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Geol 101 Sedimentary rocks cont - Coal o Plant remains...

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