Compare and contrast relative and absolute dating of rocks

16 Mar

Different spans of time on the GTS are usually marked by changes in the composition of strata which correspond to those, and indicate major geological or paleontological events, such as mass extinctions.For example, the boundary between the Cretaceous period and the Paleogene period is defined by the Cretaceous–Paleogene extinction event, which marked the demise of the non-avian dinosaurs and many other groups of life.Although they also posed new questions, the thousands of satellite photographs brought back from the Moon have permitted us to map its surface with greater accuracy than Earth could be mapped a few decades ago.We now have over 380 kg of rocks from nine places on the Moon, rocks that have been analyzed by hundreds of scientists from many different countries.Although early stratigraphers could determine the relative order of rock units and fossils, they could only estimate the lengths of time involved by observing the rates of present geologic processes and comparing the rocks produced by those processes with those preserved in the stratigraphic record.With the development of modern radiometric dating methods in the late 1940s and 1950s, it was possible for the first time not only to measure the lengths of the eras, periods, and epochs but also to check the relative order of these geologic time units.

The last modification to the geologic time scale of Figure 1 was in the 1930s, before radiometric dating was fully developed, when the Oligocene Epoch was inserted between the Eocene and the Miocene.

Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon.

The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.

Andean deformation in the study area begun around 14.5 Ma with the growth of thick-skinned structures at the western region, formed by large basement wedges that propagated along detachment horizons within the cover generating thin-skinned structures.

The development of these genetically linked thick and thin-skinned structures finished with the insertion of a third basement wedge and its associated deformation in cover rocks along the Sosneado thrust, before the extrusion of 10.8 Ma volcanic rocks.