Topic%2018_Neogene

Topic%2018_Neogene - CHAPTER TEN NEOGENE 10-1 India...

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CHAPTER TEN NEOGENE 10-1 CHAPTER 10 NEOGENE Miocene Epoch The Miocene Epoch is a period of time that extends from about 23 to 5 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain. The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words (meioon, less) and (kainos, new) and means "less recent" because it has 18% (less than the Pliocene) of modern sea invertebrates. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch. The Miocene is the first epoch of the Neogene Period. The Miocene boundaries are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Oligocene and the cooler Pliocene. In our local area area, the thick lavas flows that cover the Columbia Plateau are Miocene in age as are the world famous Clarkia plant fossils. The Miocene, Pliocene, Pleistocene, and Holocene define what formal geological period? The Clarkia fossils were deposited in this epoch. Paleogeography Continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, although South America was approaching the western subduction zone in the Pacific Ocean, causing both the rise of the Andes and a southward extension of the Meso-American peninsula. Mountain building took place in Western North America and Europe. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the American Great Plains and in Argentina. India continued to collide with Asia, creating more mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish-Arabian region between 19 and 12 mya. Subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the Messinian salinity crisis) near the end of the Miocene. The global trend was one towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture. Uplift of East Africa in the Late Miocene was partly responsible for the shrinking of tropical rain forests in that region, and Australia got drier as it entered a zone of low rainfall in the Late Miocene. Thick salt deposits show that this Ocean dried up during the late Miocene. Globally, what was the trend of the Earth’s climate during the Miocene? Flora
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This note was uploaded on 08/23/2009 for the course GEOL 102 taught by Professor Kennethsprenke during the Fall '09 term at Idaho.

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Topic%2018_Neogene - CHAPTER TEN NEOGENE 10-1 India...

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