112-pp5 - UNIVERSITY OF SOUTH ALABAMA Last time we covered....

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1 GY 112: Earth History Lecture 5: Clever Thinking 2: Plate Tectonics UNIVERSITY OF SOUTH ALABAMA Last time we covered… •The evolution of geological thinking (Pliny, Ussher, Steno, Strachy, Hutton, Smith, Lyell, Darwin, Wegener etc.) •The 5 major geological “principles” necessary for stratigraphic correlation •The 3 major types of unconformities (non-conformity, disconformity, angular unconformity) Clever thinkers: 1638-1687 1) The principle of superposition that states in any sedimentary succession that has not been overturned, the oldest strata occur on the bottom. 2) The principle of original horizontality that states sedimentary layers are originally deposited as horizontal sheets 3) The principle of original lateral continuity that states that sedimentary layers are originally deposited as laterally continuous sheets that naturally terminate against basin margins or barriers or which grade into other sedimentary layers. Clever thinkers: 1797-1875 4) Principle of cross-cutting relationships in a succession penetrated by other rock units (e.g., an igneous dike cutting across sedimentary strata) the cross-cutting body is younger than the stuff it is cutting. Clever thinkers: 1797-1875 5) Principle of Inclusions: A rock containing fragments of “country rock” (e.g. a pluton might rip off some of the surrounding rock that it is pushing through and incorporate it into the magma before cooling), must be younger than the country rock it contains. Clever thinkers:
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112-pp5 - UNIVERSITY OF SOUTH ALABAMA Last time we covered....

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