Sedimentary Rocks Erosion Transport Deposition Lithification Clastic Sedimentary Rx – from broken pieces Chemical Sedimentary RX – from dissolved stuff Biochemical Sedimentary Rx – from dissolved stuff

Clastic Sedimentary Rocks – pieces of mins (quartz, feldspars, mica, etc.) & clay gravel conglomerate sands sandstone silt siltstone clay shale, mudstone Sizes sorted by transportation

Chemical Sedimentary Rocks Evaporites – Halite, Gypsum Biochemical Sedimentary Rocks Limestone - Calcite Chalk - Calcite Chert - Quartz

Group PRS In which group of sedimentary rocks do most of the weathering products of most felsic (rhyolitic) rocks end up? A. Clastic B. Chemical C. Biochemical

Metamorphic Rocks – heat and pressure alters other rx Heat and pressure can come from burial or contact – cause minerals to grow, recrystallize, or change into new mineral. Name of MM rock depends on texture and minerals in it. Minerals depend on protolith and amount of temp & press Contact MM – due to igneous contact Regional MM – burial Foliation – parallel alignment of minerals due to pressure- not all minerals will do this (mostly micas, feldspars do)

MM Rocks include Marble – MM limestone Slate – MM shale Quartzite – MM sandstone Schist – usually can’t tell protolith

You have found a rock. It appears to be composed of Quartz, Potassium Feldspar, and a little mica. The minerals have planar irregular boundaries that appear to interlock with one another like pieces of a jigsaw puzzle. There is no obvious alignment of any minerals. What is the rock? A. Igneous B. Sedimentary C. Metamorphic

May form from basaltic magma Form at the earth’s surface Have texture Made of small grains Granite is an example Form as a result of melting May form from rhyolitic magma May form in presence of water Exposed at surface only after erosion Contains minerals Classified based on density of minerals Dark colored have low silica content Contains visible grains both volcanic plutonic both/neither neither

TIME

Relative Time vs. Absolute (Numerical) Time Bishop Ussher – Earth formed 4004 B.C. –October 23 – using Biblical history GROUP QUESTION: Think of another way to come up with a minimum age for the earth (do not use radioactivity)

Atoms

Isotopes 6 protons 6 protons 6 protons 6 neutrons 7 neutrons 8 neutrons

PRS If an atom with 19 protons and 20 neutrons is an isotope of Potassium, Which of the following is another isotope of Potassium? 20 p, 19 n 20 p, 21 n 19 p, 22 n 20 p, 22 n 18 p, 22 n

Radioactivity Parent Daughter

Need to know 4 things Sample had some parent at start Sample has been “closed system” Decay rate of parent-daughter pair Parent-daughter ratio at start Need to measure 1 thing Parent-daughter ratio now

Industrial revolution added C12 – diluting the C14 Nuclear Bomb Tests added C14

C14 Calibration

Why don’t geologists use 14 C to date rocks? Half life is too long Rocks aren’t closed systems Rocks don’t have any Carbon Rocks don’t get carbon from atmosphere Rocks have too much 14 C

K – Ar dating HL 1.26 BY Daughter is noble gas

(compiled from Dalrymple, 1991) Technique Age Range (billion years) uranium-lead 3.60±0.05 lead-lead 3.56±0.10 3.74±0.12 3.62±0.13 rubidium-strontium 3.64±0.06 3.62±0.14 3.67±0.09 3.66±0.10 3.61±0.22 3.56±0.14 lutetium-hafnium 3.55±0.22 samarium-neodymium 3.56±0.20 (compiled from Dalrymple, 1991)

Geologic Time Scale Pieced together through correlation Dates come from radioactivity

Correct answer for 8.3 Youngest J E C A G B I D F H Oldest