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Unformatted text preview: Eustatic Sea level: Global sea level change, Relative sea level: local sea level change • Example: Hudson Bay- the relative sea level was growing b/c of the land displacement, caused the ocean level to rise, but the eustatic sea level other than Hudson bay is decreasing. Isotopes and sea-level change: Oxygen-18 as well as some Carbon isotopes are good indicator of sea level change • the shells trap in Oxygen 18 in them and when the organism leaves the shell or dies, the leftover shells are left behind to date the surrounding rock layers. Sea level orders: Lowest order- usually the longest period of time, marks the breaks between geological periods. 2 nd order- shorter periods, in between geological periods. Da Vinci: He found small shells on land similar to shells that are found at the shore raised questions of how this could have happened Nicolaus Steno: Father of stratigraphy, wrote the Steno’s Laws and Corollaries: law or original horizontality, lateral continuity, superposition cross- cutting relations and included fragments • Original Horizontality: gravity makes sediment follow the sediment beds, usually at first horizontally. • Lateral Continuity: sediment will have continuity unless sediment runs out or an event lead to a break in layers, like a river or something similar to that • Superposition: in a sequence of rock layers, the oldest rock is located at the bottom and the youngest rock is on top unless it has been overturned • Cross cutting Relations: Any fault or igneous intrusion must be younger than the rock it cuts through • Included Fragments: fragments/ clasts that are included within a rock are older than the rock they are included in James Hutton: Came up with the idea of uniformitarianism, considered as father of modern geology • Uniformitarianism: the assumption that the natural processes operating in the past are the same as the ones that are operating in the present “the present is the key to the past” • Principle of Faunal Succession: fossils are different from each other in the following layers but if in the same place in time then the fossils in other continents are the same William Smith: Started naming rock formations began in England; dealt with lithography • Lithographic Units: must be a body of like strata that can be traced over appreciable distances (must be a reasonable distance though), has a recognizable contacts with units above and below, but doesn’t have to be of one lithology • Formations: may or may not be the same age everywhere it is encountered;...
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This note was uploaded on 04/08/2008 for the course GEO 202 taught by Professor Staff during the Spring '08 term at Mines.
- Spring '08