THE PLIO-HOLOCENE LARGE MAMMALS OF THE WESTERN EURASIA: MACROECOLOGICAL AND EVOLUTIONARY ANALYSES OF THE FAUNAS
The climate during the Plio-Pleistocene was deeply influenced by the so called Milankovitch cycles (Zachos et al.,2001). These are combinations of different astronomical phenomena involving the variation of the Earth’s orbital eccentricity, the axis obliquity and precession. The first phenomenon was...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | Italian English |
| Published: |
2009
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| Online Access: | http://www.fedoa.unina.it/4197/ http://www.fedoa.unina.it/4197/1/Carotenuto_Francesco.pdf https://doi.org/10.6092/UNINA/FEDOA/4197 |
| Summary: | The climate during the Plio-Pleistocene was deeply influenced by the so called Milankovitch cycles (Zachos et al.,2001). These are combinations of different astronomical phenomena involving the variation of the Earth’s orbital eccentricity, the axis obliquity and precession. The first phenomenon was estimated to occur every 400-100 Ka, whereas the others occur over a time period of 41 and 23-19 Ka, respectively. These astronomical variations influenced the Earth-Sun distance and the angular incidence of solar rays with a net effect on the global climate change (Zachos et al., 2001). The Early Pliocene was characterized by a decrease of the global temperature, a trend that began during the Late Miocene. The measure of the mean 16O/18O values indicates a trend of warmer climate until 3.2 Mya, the latter that represents the onset of a new temperature cycle. During these cycles the ice sheet expanded and contracted according to the variation of the mean global temperature. Indeed, in the Middle Pliocene, the ice sheets began to cover the Northern Hemisphere, an event indicated as NHG (North Hemisphere Glaciation) (Shackleton et al., 1998; Maslin et al., 1998; Zachos et al., 2001). At ~2.5 Mya the oscillations of the temperature became quite a regular pattern determining the alternation between warmer (Interglacials) and cooler (Glacials) time periods, that were to characterize the Pleistocene. Some 1 May (period coincident with the Jaramillo Event of Earth’s Magnetic Field inversion) the time interval of a complete climatic cycle changed its duration from the 41-23-19 Kya., to a new longer cycle of 100 Kya, probably determined Earth’s orbital eccentricity variation. With the increase of the duration of the cycles the mean global temperatures reached more extreme values and there were stronger climate ranges between warm and cold periods. Moreover, the measures of the oxygen isotopes ratios confirm a net decrement of mean temperature values recorded from the Late Pliocene to the Recent (Zachos et al., 2001). The ... |
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