GEOL 101 Lecture Notes - Lecture 31: Lithostratigraphy, Erosion Surface, Unconformity
Document Summary
Geologic record: the fact that earth has changed through time has become clear based on evidence in the geologic record, geologic record is the record of events preserved in rocks. Although all rocks are useful in deciphering the geologic record, sedimentary rocks are especially useful. Learning to better interpret the record is still going on. Age of lava ows, sills: determining relative ages of lava ows, sills, and associated sedimentary rocks uses alteration by heat and inclusions, a lava ow forms in sequence with sedimentary layers. Principle of inclusions- inclusions or fragments in a rock are older than the rock itself. Sill- will heat the rocks above and below it. Interval of time not represented by strata is hiatus. Types: disconformity- surface separating younger from older rocks, parallel, nonconformity- erosional surface cut into metamorphic intrusive rocks and covered by sedimentary rocks, angular- erosional surface on tilted or folded strata over which younger rocks were deposited.
