An Introduction to Geology

Sedimentary Rocks

Back to the Rock Cycle

Sedimentary processes

1. Weathering

2. Transportation

3. Deposition

4. Lithification

A. Existing rocks

B. Biological materials

C. Chemical precipitates

OF

Sedimentary processes

Common sedimentary minerals

Quartz Feldspars

Micas

Calcite

Hand specimens

First impressions?

Weathering

Physical /

Mechanical

Weathering

Chemical /

Biological

Weathering = clasts

Transportation

Transport mechanisms

Rivers = fluvial

Seas = marineMississippi delta

Transport mechanismsAEOLIAN (wind)Can only transport small grains

GLACIAL (ice)Huge volumes of sediment

Transportation

Proximity + velocity = grain size

Transport time = maturity

Textural maturity:

Transport time = maturity

Mineralogical maturity:

DepositionTransportation into basins

LithificationDeposition (+ deposition + deposition) = burialDeposition (+ deposition + deposition) = burial

Burial = compaction + cementationBurial = compaction + cementation

Compaction

Stylolites in chalk

Cementation•Mineral precipitation into pore spaces:•e.g. calcite, quartz, e.g. calcite, quartz, haematitehaematite

Hand specimens

Second impressions?

Sedimentary rocks

Grain sizeGrain size ClassificationClassification ExampleExample

>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate

Particle size, shape and composition

Conglomerate

Sedimentary rocks

Grain sizeGrain size ClassificationClassification ExampleExample

>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate

0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone

Particle size, shape and composition

Sandstone

Sedimentary rocks

Grain sizeGrain size ClassificationClassification ExampleExample

>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate

0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone

0.004-0.06 mm0.004-0.06 mm ArgillaceousArgillaceous SiltstoneSiltstone

Particle size, shape and composition

Siltstone

Sedimentary rocks

Grain sizeGrain size ClassificationClassification ExampleExample

>2 mm>2 mm RudaceousRudaceous ConglomerateConglomerate

0.06-2 mm0.06-2 mm ArenaceousArenaceous SandstoneSandstone

0.004-0.06 mm0.004-0.06 mm ArgillaceousArgillaceous SiltstoneSiltstone

<0.004 mm<0.004 mm ArgillaceousArgillaceous ClaystoneClaystone

Particle size, shape and composition

Claystone

Bituminous shales, Saltwick Nab, near Whtby

Sedimentary rock types1. Clastic (or detrital)

Sedimentary rock types1. Clastic (or detrital)

Sedimentary rock types2. Biogenic (or organic)

Sedimentary rock types2. Biogenic (or organic)

Sedimentary rock types3. Chemical (precipitates)

Hand specimens

What sedimentary rock type is your specimen?

Sedimentary structures

Bedding

Sedimentary structuresCross-bedding

Sedimentary structuresCross-bedding

Sedimentary structures

Ripple marks

Sedimentary structures

Mud cracks

Sedimentary structuresShell beds

Sedimentary structuresTrace fossils

Sedimentary UK

Next weekUnder Pressure: Metamorphic Rocks