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Sedimentary Rock

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Presentation on theme: "Sedimentary Rock"— Presentation transcript:

1 Sedimentary Rock

2 Sedimentary Rocks are the product of sediment deposition, diagenesis, and lithification

3 Oceans rise and fall, lakes come and go, streams run and disappear, deserts become forests and forest become swamps…all these changes will be recorded in sedimentary rocks

4 Sedimentary rock contains sediment grains, cement holding them together, and empty space called “pores”

5 To understand Earth history, a geologist seeks to interpret the “Environment of Deposition” of a sedimentary rock…this reveals something about changes occurring on Earth’s surface Eolian Environment – grains of uniform size “well sorted” Coastal Environment – grains coarser and of mixed size Stream Environment – grains much coarser and “poorly sorted”

6 Glacial Environment – grains very coarse with no sorting, but usually rounded Landslide Environment – grains very coarse with no sorting, with no rounding Marsh/Mudflat Environment – grains very fine

7 Evaporite environment – chemical sediments Reef environment – biological sediments Deep sea environment ?? – Plankton sediment and clays from land

8 Sedimentary Structures…. Sedimentary rocks tend to form layers or strata…each layer records a depositional event Cross-beds – former dunes

9 Ripple marks Mud cracks modern ancient

10 Sediment becomes sedimentary rock…the texture and composition of the sediment determine the type of sedimentary rock

11 Two types of sedimentary rock – Clastic Sedimentary Rock – made of pieces of broken crust Biochemical Sedimentary Rock – made of precipitated minerals Conglomerate Rock Salt

12 Clastic Sedimentary Rock Conglomerate/Breccia – gravel texture Sandstone – sand texture Shale – silt/clay texture Biochemical Sedimentary Rock Limestone – CaCO 3 composition Chert – SiO 2 composition Coal – Carbon composition

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14 Pressure forms coal How does coal form?

15 Coal strip mine…

16 Environments of deposition Sedimentary texture Sediment composition Global Climate history Clastic – Biochemical sedimentary rox Breccia/Conglomerate Sandstone Shale Limestone Chert Coal How does coal form? Sedimentary structures

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19 But why was there an ice age?

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21 Ice stores O 16 so that oceans are O 16 depleted in an ice age

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23 + O 18 /O 16 - CaCO 3 Layer by layer sampling of plankton reveals oxygen isotope record Periodicity of 100,000 yrs

24 100 kyrs 41 kyrs 21 kyrs

25 These were made during an ice age!


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