SEDIMENTARY ROCKS

TERMS Weathering: breakdown of pre-existing rock Physical or chemical breakdown Erosion: transport of sediment on Earth’s surface

SEDIMENTARY ROCKS Introduction Detrital Rocks Chemical and Biochemical Rocks Lithification

Sedimentary Rocks Introduction

INTRODUCTION Origin Only form at Earth’s surface PSCI 131: Sedimentary Rocks INTRODUCTION Origin Only form at Earth’s surface Weathering of pre-existing rock into soluble and insoluble sediments Erosion of sediments Deposition of solid sediment Precipitation of dissolved sediment

INTRODUCTION Textures PSCI 131: Sedimentary Rocks INTRODUCTION Textures Clastic: made of grains held together by cement or compaction Nonclastic: usually made of interlocking mineral crystals

Sedimentary Rocks Detrital Rocks

Detrital Rocks “Detrital” from “detritus” - debris PSCI 131: Sedimentary Rocks Detrital Rocks “Detrital” from “detritus” - debris Composed of solid sediment grains; distinguished by size of grains All detrital rocks have a clastic texture Detrital rock with smaller grains Detrital rock with large grains

Shale Most abundant sedimentary rock Made of clay grains PSCI 131: Sedimentary Rocks - Detrital Shale Most abundant sedimentary rock 2/3 of all sedimentary rock is shale Made of clay grains Microscopic sheets From chemical weathering of feldspar

Shale PSCI 131: Sedimentary Rocks - Detrital Scanning electron microscope image of shale showing flat clay grains. Scale bar is 0.005 cm. From: claysandminerals.com

Sandstone Cemented sand-size grains Sand: 1/16mm – 2mm diameter PSCI 131: Sedimentary Rocks - Detrital Sandstone Cemented sand-size grains Sand: 1/16mm – 2mm diameter Quartz is predominant mineral

CONGLOMERATE/BRECCIA PSCI 131: Sedimentary Rocks - Detrital CONGLOMERATE/BRECCIA Cemented gravel-size grains Gravel: greater than 2mm CONGLOMERATE has rounded gravel BRECCIA has angular gravel

Sedimentary Rocks Chemical Rocks

Chemical and Biochemical Sedimentary Rocks PSCI 131: Sedimentary Rocks Chemical and Biochemical Sedimentary Rocks Dissolved sediment precipitates out of solution as crystals Chemical rocks: evaporation, chemical activity Biochemical rocks: growth of shells

Chemical Rocks: Crystalline limestone PSCI 131: Sedimentary Rocks – Chemical rocks Chemical Rocks: Crystalline limestone Nonclastic texture Interlocking calcite crystals Precipitated from seawater

Chemical Rocks: Microcrystalline limestone PSCI 131: Sedimentary Rocks – Chemical rocks Chemical Rocks: Microcrystalline limestone Nonclastic texture Interlocking microscopic calcite crystals Precipitated from seawater

Chemical Rocks: Travertine PSCI 131: Sedimentary Rocks – Chemical rocks Chemical Rocks: Travertine Nonclastic texture Porous Precipitated from groundwater in caves

Other chemical sedimentary rocks PSCI 131: Sedimentary Rocks – Other chemical rocks Other chemical sedimentary rocks Rock gypsum and rock salt Nonclastic texture Interlocking mineral crystals Evaporation of salt water “Evaporites” Bonneville Salt Flats, the ancient floor of Lake Bonneville, now mostly evaporated

Biochemical rocks: Coquina PSCI 131: Sedimentary Rocks – Biochemical rocks Biochemical rocks: Coquina Clastic texture Shell fragments & cement Fragile Shorelines

Biochemical rocks: Fossiliferous limestone PSCI 131: Sedimentary Rocks – Biochemical rocks Biochemical rocks: Fossiliferous limestone Clastic texture Shell fragments, whole shells, mud matrix, & cement Hard Shallow ocean

Biochemical rocks: Chalk PSCI 131: Sedimentary Rocks – Biochemical rocks Biochemical rocks: Chalk Clastic texture Microscopic shells (plankton) Very soft Deep ocean

Chert and flint Composed mainly of microcrystalline quartz PSCI 131: Sedimentary Rocks-Other biochemical rocks Chert and flint Composed mainly of microcrystalline quartz Nonclastic texture Can be chemical or biochemical Very hard FLINT CHERT

Sedimentary Rocks Lithification

Lithification How sediment becomes rock “Lith” = stone PSCI 131: Sedimentary Rocks - Lithification Lithification How sediment becomes rock “Lith” = stone

Lithification Processes PSCI 131: Sedimentary Rocks - Lithification Lithification Processes Compaction Cementation

PSCI 131: Sedimentary Rocks - Lithification Begins with deposition & burial of sediment under more sediment

Compaction Decreases porosity (empty space) Drives out water PSCI 131: Sedimentary Rocks - Lithification Compaction Decreases porosity (empty space) Drives out water Can make flat grains stick together

Cementation New crystals form between grains PSCI 131: Sedimentary Rocks - Lithification Cementation New crystals form between grains Precipitation out of groundwater Fills in remaining porosity Original sand grain Cement crystals From: northstonematerials.com From: unibe.ch

End of Sedimentary Rocks