GEOS 1004 Lecture Notes - Lecture 16: Geologic Time Scale, Radiometric Dating, Relative Dating

• School: Virginia Tech
• Department: Geosciences
• Course: GEOS 1004
• Professor: James A. Spotila

Document Summary

Lecture 16: sedimentary rocks ii and geologic time. Sedimentary features: stratigraphy: sedimentary layers (bedding) are laid down bottom youngest on top (superposition) and are normally close to horizontal. (cid:498)original horizontality(cid:499) (cid:498)cross cutting relationships(cid:499) = younger rocks or structures cut across layers. Superposition, horizontality, and cross-cutting relationships define relative time in rock sections. Look-up items: define "superposition", "original horizontality", and "cross cutting relationships. " Superposition: the order in which sedimentary strata are superposed one above another. Original horizontality: layers of sediment are originally deposited horizontally under the action of gravity cross cutting: eologic feature which cutsanother is the younger of the two features. It is a relative dating technique in geology: cross bedding: layering within layers, geometry of layers; indicate type (streams, wind) and direction of transport, graded bedding = layers sorted by grainsize; denote flood events. Ripples, cracks, fossils, etc. indicative of water type (e. g. fresh or marine), water depth, current velocity, climate, etc.