ERS120H5 Lecture Notes - Gneiss, Unconformity, Xenolith
Document Summary
O putting events in order to figure out time span: easier and cheaper, numerical age, utilizing dates, expensive and labour intensive. Telling time: geologic time and rock dating methods. Measure time: relative age, erosion, basalt i, basalt ii, conglomerate, breccia, erosion, tilting, limestone, shale, sandstone, erosion, gneiss. The principle of cross cutting relationships any features which cuts across other rocks and features must be younger (dike) Any piece of rock (inclusion or xenolith) included within another rock must be older than the rock in which it is incorporated. The principle of unconformities an unconformity is rock interface which represents a gap in the geologic record, like pages missing from a book large age gap between rock layers. Sedimentary layers (and lava flows) are usually originally laid down horizontally. If they are not now horizontal, they have been deformed over local area they are flat.
