Minerals & Rocks, Sedimentary Features

What is a Mineral? These are substances that: 1. Are Naturally Occurring (usually) 2. Are Solid at Room Temperature (usually) 3. Have a Specific Chemical Composition 4. Have an Ordered Atomic Structure 5. Are Inorganic (usually)

What’s your Mineral? Identifying a Mineral Using: A. Physical Properties 1. Crystal habit 2. Streak 3. Luster 4. Cleavage 5. Density 6. Hardness 7. Color 8. Others: magnetism, taste, flexibility

Three Basic Rock Types 1.Igneous 2.Metamorphic 3.Sedimentary

Igneous Rocks 1.Formed from the cooling and solidification of magma/lava (see texture, mineral content) a. intrusive (plutons, dikes) b. extrusive (lava flows) c. two-stage (porphyritics)

Intrusive Igneous Rocks Magma body forms within crust, slowly cools under ground (i.e., pluton, dike, sill)

Extrusive Igneous Rocks Magma escapes opening in Earth’s crust and flows as lava

Metamorphic Rocks Protolith is changed physically and/or chemically while being subjected to high heat and/or pressure 1. Metamorphic processes include:

a. regional

b. contact & metasomatic

Sedimentary Rocks Lithification – loose sediment becomes rock through: a. compaction: weight of overlying deposits compresses sediment, pushing out fluids and reducing porosity

compaction and/or C ementation - sediment “cemented” by minerals in solution (loss of porosity) Cementing minerals include: quartz (silica), carbonate, iron oxide, clay

Sedimentary Rocks Classification depends on depositional processes: Clastic – particles (clasts) transported by moving fluids…

Biochemical – accumulation of residues from: skeletons of siliceous organisms (chert) Radiolarians Diatoms

Biochemical – accumulation of residues from: dissolved skeletons of invertebrates (limestone) Carbonate “mud” Ostracod Foraminiferans

Biochemical – accumulation of residues from: decayed plants (coal) Coal Swamp – Pennsylvanian Period (300 Ma) central Pennsylvania

Chemical – precipitation of sediment from supersaturated solutions… Salt Mine - Poland Bonneville Salt Flats – Utah

“ Other” – sediment accumulation through occasional processes… Eolean – sand dunes Glacial – morraines

“ Other” – sediment accumulation through occasional processes… Volcanic Eruptions Mt. Pinatubo, Philippines Pyroclastic flow

“ Other” – sediment accumulation through occasional processes… Extraterrestrial Impacts Chicxulub, Yucatan Penninsula 65 Ma Meteor Crater, AZ - 45 Ka

What’s in that (Sedimentary) Rock? Mineral comp. Grain size Grain sphericity Grain sorting Matrix

Sedimentary Structures Bedding plane structures: Ripples Raindrops Mud Cracks

Within bedding structures Planar Bedding Cross Bedding Imbrication Graded Bedding Cut and Fill

Biological structures 1 Ophiomorpha 2 Diplocraterion (“yo-yo”) 3 Skolithos 4 Monocraterion Burrows Dinosaur Trackways

Put the Puzzle Together Rock exposure Fossil Turtle Ammonite Mosasaur Bird Bone Plesiosaur

Central South Dakota 73 Ma