Sedimentary Rocks Interpretations

What do Sedimentary Rocks Record? Source of sediment Erosion and Transport Agent Distance of Transport Depositional Environment Paleogeography/Tectonic Setting

Interpretation of Composition Detrital Rocks: Source of sediment Exposure to Weathering (Distance of Transport) (Type of Climate)

Note About Detrital Rock Color & Composition Grain Size Smaller is often darker Composition Carbon - black or brown Quartz - tan, clear, white Orthoclase - orange Depositional Environment Iron on land - red Iron in deep, oxygen poor water - green

Interpretation: Grain Size Gravel Sand Silt Clay High Energy Low Energy River, Beach River, Beach, Desert Delta, Shallow Ocean Deep Ocean, Lake, Swamp

Detrital Rock Names (Based Primarily on Grain Size) Gravel Sized: Conglomerate Sand Sized: Sandstone Mud Sized: Mudstone Siltstone Shale

Interpretation: Sorting Poorly Sorted Well Sorted Transport Agent Gravity and Glaciers (and Rivers) Water and Wind

Clast Supported Conglomerate (River Deposits)

Matrix Supported Conglomerate (Glacial/Landslide Deposits) 2.2 Gyr Conglomerate “Modern” Glacial Sediments

Interpretation: Grain Roundness Interpretation: Distance of Transport Short Far

Limestone Crystalline Limestone Fossiliferous Limestone Chalk

Formation of Limestone Calcite Precipitates in Warm Water Water Under Low Pressure (Shallow) Or It is secreted by biological organisms Clams, Mussels, Scallops, etc. Corals Foraminifera

Limestone Represents: Shallow Tropical Ocean

Chalk (Coccolithophores)

Black Sea

Travertine (Limestone)

Chert (Flint, Jasper, Agate…)

Diatom Steletons

Chert Represents Deep Ocean

Evaporites: Bonneville Salt Flats, Utah Rock Gypsum Rock Salt Isolated, Arid, Salty Sea/Lake

Peat and Coal Swamp, Bog

Intermission: Quiz What can you say about the history of this rock? Deposited in a beach/river or desert, very far from the source of the sediment. Quartz Sandstone

Intermission: Quiz What can you say about the history of this rock? Deposited in a quiet water environment (deep ocean, lake, lagoon). Dark color implies oxygen-poor environment, rich in organic material. Shale

Intermission: Quiz What can you say about the history of this rock? Deposited in a shallow tropical ocean. Limestone