105_06-weathering-soil-sed_rx_part_2

105_06-weathering-soil-sed_rx_part_2

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Unformatted text preview: ediments How How does sediment turn into rock? – Compaction – Cementation – Crystallization All processes remove pore space between pore grains. 5 Lithification of Sediments Compaction Compaction – Reduces the volume of sediment Cementation of Rocks Cementation Cementation – Minerals precipitate between grains as groundwater moves through pore spaces Cementation of Rocks Pore space Calcite cement Shells Lithification of Rocks Crystallization Crystallization – Minerals precipitate from solution to form entire rock body. (Ex: Limestone) Photomicrograph Types of Sedimentary Rocks Clastic Clastic – Fragments of sedimentary, metamorphic, and igneous rocks cemented together Groups of Sedimentary Rocks Clastic Clastic – Consist of fragments of sedimentary, metamorphic, and igneous rocks – Pieces can have sizes from fistfistsize to barely visible: classification - names – Silicates There There are lots of them Resistance Resistance to weathering (quartz) Chemical Chemical (inorganic) – Precipitants from dissolved minerals Limestone, Limestone, Halite Biochemical Biochemical (organic) – Plants and animal shells or skeletons Coal Coal 6 Detrital Rocks Conglomerates Conglomerates – Grains are rounded Detrital Rocks Sandstone Sandstone – Silicate minerals – 0.64 – 2 mm – Quartz sandstone (Arenite) > 90% Quartz 90% Breccias Breccias – Grains are angular – Feldspathic sandstone (Arkose) ~ 25% Feldspar 25% ~ 75% Quartz 75% – Lithic sandstone (Graywacke) ~ 25% dark fragments (volcanic) 25% ~ 20-30 % Feldspar 20~ 45-65% Quartz 45- Detrital Rocks Siltstone Siltstone – Like mudstone, but grains barely visible Mudstone Mudstone - Shale – Clay minerals and mica – < 0.004 mm (not visible) – Low energy Lake, Lake, lagoon, floodplains, deep marine Shale exposure Chemical and biochemical sedimentary Rocks Consist Consist of ions and compounds released by chemical weathering – precipitated by chemical reactions (inorganic) or by – metabolism of organisms (organic) Chemical and biochemical sedimentary Rocks Inorganic Inorganic – Very fine grained – Limestones Calcite Calcite Bahamas Bahamas and Florida Caves Caves – Evaporates Halite Halite Gypsum Gypsum 7 Salt lake: formation of evaporites Salt lake: formation of evaporites 8...
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This note was uploaded on 05/18/2011 for the course GEOL 105 taught by Professor Jack during the Spring '08 term at University of Louisiana at Lafayette.

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