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2. Evidence of Former Depositional Environments Deep Marine Black Shales Pelagic Muds/Oozes Greywackes Mature Immature Laminations Graded Bedding ( some.

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Presentation on theme: "2. Evidence of Former Depositional Environments Deep Marine Black Shales Pelagic Muds/Oozes Greywackes Mature Immature Laminations Graded Bedding ( some."— Presentation transcript:

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2 2. Evidence of Former Depositional Environments

3 Deep Marine Black Shales Pelagic Muds/Oozes Greywackes Mature Immature Laminations Graded Bedding ( some evidence of cross bedding & ripple marks) Sole Marks Graptolites Slow build up of sediment apart from turbidites

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11 Carboniferous 360 – 290 MYA Carboniferous Limestone Brachiopods Crinoids Ammonoids Colonial coral

12 Upper Carboniferous limestone mudstone sandstone Delta top / swamp Fluvial channel fill Delta front Prodelta Offshore

13 Upper Carboniferous Delta top / swamp Fluvial channel fill Delta front Prodelta Offshore Turbidity currents

14 Upper Carboniferous Carboniferous Limestone Brachiopods Crinoids Ammonoids Colonial coral Millstone Grit (ssts) Medium-grained Arkose Quartz Feldspar Weak cross bedding Mudstones Shales

15 Suggest the environment of deposition of the sediments shown in Fig. 1c and give evidence for your conclusion. (5) Environment: Deltaic (1) Evidence: Coal swamp/rootlets/complete fossil plants (1) Coarsening up sequence (1) Cross-bedded sands (1) Marine sediments/bivalves (1) Marine to freshwater (1) Shallowing of water (1)

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17 limestoneshale & siltstonesandstoneconglomeratecoal Coal Measures Texture Crystalline, fine- grained, chemical bioclastic Fragmental, fine- grained, well sorted Fragmental, coarse sand, moderately sorted, sub-rounded, smooth surface Fragmental, coarse- grained, poorly sorted, sub-rounded, smooth surface Chemical Mineralogy CaCO 3 clay & siltQuartz, feldspar rock fragments organic material Structures Bedding Tectonic joints cross bedding coarsening upwards imbrication Seat earth (fossil soils) Fossils Goniatites Corals Crinoids Brachiopods Marine bivalvesFreshwater bivalvesGiant lycopods (Lepidodendron) Tree ferns Amphibians, early reptiles Spiders, giant flying insects Millstone Grit Texture Fragmental, coarse sand, moderately sorted, smooth surface, sub-rounded Mineralogy Quartz, feldspar Structures Cross-bedding Fossils Freshwater bivalves Carboniferous Limestone Texture Crystalline fine-grained, chemical, bioclastic Mineralogy CaCO 3 Structures Bedding, tectonic joints Fossils Goniatites Corals Crinoids Brachiopods 363 Ma 290 Ma 325 Ma 315 Ma

18 Devonian 409 – 360 MYA Sandstones & conglomerates Limestones & Marine fossils

19 Devonian mya South of equator 10-20º Arid/desert climate – similar to SW USA (New Mexico/Texas) Old Red Sandstone (ORS) Continent Rapid erosion of Caledonian mountains (Caledonian orogeny) Rivers & lakes in basins between mountains Tropical ocean to south (Rheic Ocean) Desert sandstones – lack of fossils Alluvial sandstones – river deposits Limestones – brachiopods Shales – lake deposits, primitive fish, land plants, insects on land & first winged insects

20 Alluvial Environments (meandering rivers) Lithology: Texture: Mineralogy: Structures: Fossils:

21 conglomerates well-sorted red sandstones desiccation cracks & calcrete cross bedding repeated cycles alluvial fan deposits formed at edge of Caledonian mountain area Old Red Sandstone Deposits

22 1 cm ORS sandstone, Orkney Medium to fine grained red sandstone with cross bedding

23 50 cm ORS conglomerate, Aberdeen Boulder sized clasts of quartzite, granite, rhyolite & andesite

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25 Devonian Marine Deposits


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