The Holocene Epoch is a geologic period that extends from the present back about 10,000 radiocarbon years. The beginning of the Holocene was punctuated by the Younger Dryas cold period, the final part of Pleistocene epoch. The end of the Younger Dryas has been dated to about 9600 BC (11550 calendar years BP). However, evidence for the Younger Dryas is not clear cut anywhere other than in the Northern Hemisphere.
The Holocene starts late in the retreat of the Pleistocene glaciers. The Holocene is the fourth and last epoch of the Neogene period (second epoch of the unofficial Quaternary sub-era). The name is derived from the Greek holos (entire(ly)) and ceno (new). It has also been called the "Alluvium Epoch".
Paleontologists have defined no faunal stages for the Pleistocene or Holocene.
Geology
Continental motions are negligible over a span of only 10,000 years -- less than a kilometer. However, world sea levels rose about 35 meters (110 feet) in the early part of the Holocene due to ice melt. In addition, many areas above about 40 degrees latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 meters over the late Pleistocene and Holocene.
The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known from Vermont, Quebec, Ontario, and Michigan. Other than higher latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain, and cave deposits. Holocene marine deposits along coastlines are rare because the rise in sea levels during the period exceeds any likely upthrusting of non-glacial origin.
Apart from temporary incursions, Post-glacial rebound in the Scandinavia region resulted in the evolution of the Baltic Sea. The region continues to rise, still causing weak earthshakes across Northern Europe.
Climate
Although geographic shifts in the Holocene were minor, climatic shifts were very large. Ice core records show that before the Holocene there were global warming and cooling periods but climate changes became more regional at the start of the Younger Dryas. However, the Huelmo/Mascardi Cold Reversal in the Southern Hemisphere began before the Younger Dryas and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. There appears to be a south to north pattern, with southern latitudes displaying maximum warming a few millennia before the Northern Hemisphere regions. It is also possible that the Holocene warming is merely another interglacial period and does not represent a permanent end to the Pleistocene glaciation.
Habitable zones expanded Northwards. Large mid-latitude area such as the Sahara that were previously productive became deserts. The epoch started with large lakes in many areas that are now quite arid.
Animal and plant life did not evolve much during the Holocene, but there were major shifts in the distributions of plants and animals. A number of large animals including mammoths and mastodons, saber tooth cats, and giant sloths disappeared in the late Pleistocene and early Holocene -- especially in North America where common animals that survived elsewhere (including horses and camels) became extinct. Throughout the world, cooler climate ecosystems that were previously regional have been isolated in higher altitude ecological "islands."
Human developments
The beginning of the Holocene corresponds with the beginning of the Mesolithic age in most of Europe; but in regions such as the Middle East and Anatolia with a very early neolithisation, Epipaleolithic is used in place of Mesolithic. Cultures in this period include: Hamburgian , Federmesser, and the Natufian culture.
Both are followed by the aceramic Neolithic (Pre-Pottery Neolithic A and Pre-Pottery Neolithic B) and the pottery Neolithic.
See also
Last updated: 09-12-2005 02:39:13
