Holocene period

FIGURE 14.62 Evidence of rapid climate changes at the start of the Holocene period 11,600 years before the present (bp) (a) electrical conductivity (b) rate of accumulation of snow (c) calcium concentration. The depth of the ice cores is shown on the bottom axis and the corresponding age in years before the present on the top axis (adapted from Taylor et al., 1997). 

Variations in Pb concentration in Dome C ice cores during the Wisconsin/ Holocene transition (27,000 to 4000 years BP) were determined with the dependable approach developed by Boutron s team (61). The uncertainty budget for these measurements as caused by contamination events was thought to be 10% for high Wisconsin and 50% for the very low Holocene Pb concentrations, respectively. Before anthropogenic contributions started, it is estimated that Pb was primarily due to volcanic activity (Holocene period) and soil dust (late Wisconsin and Holocene periods). 

Boulder Clays, Of glacial origin, Boulder Clays occur in the Recent or Holocene Period. (See p. 76). 

The most recent geological period of our planet Earth is called "Quaternary" which is divided into two subsections. The older one is named "Pleistocene" and the younger one "Holocene". The Pleistocene period started about 1.8 million years before now and ended just 10,300 years before now. Consequently, the Holocene period covers the last 10,000 years. The Pleistocene is also called Glacial epoch or formerly Ice age. 

Foraminifera are also important in marine geochemistry studies, and Li isotopes have been measured in the shells of a variety of these organisms. The first report of this kind (You and Chan 1996) gave data for four Pleistocene samples of H obliquiloculata 5 Li = +19.3 to +23.0 for two glacial period samples and +26.6 to +42.4 for two interglacial samples (data without blank correction). The species effect interpreted by Marriott et al. (2004) in corals has also been suggested for forams. In the study of Rosier et al. (2001), core-top (i.e., Holocene)P. obliquiloculata samples yielded isotopic compositions close to modem seawater (5 Li = +27.8 to +31.1), whereas samples of G. tumida from the same samples had values of up to +50.5. 

FIGURE 14-60 Relationship of ice core depth to years before the present (bp) and to the type of ice for the Central Greenland Ice Sheet. The Holocene and Wisconsin periods are also marked (adapted from Gow et at., 1997). 

The Quaternary Period is subdivided into the Pleistocene Epoch and, commencing at 10,000 years ago, the Holocene Epoch. The Holocene is synonymous with the Postglacial or present interglaciation. ... 

It is important to realise that clay can be exposed to many processes after it has been depos-ited. The periods are the Miocene Epoch (26 - 7 million years old), the Pliocene Epoch (7-2 millions years old), the Pleistocene Epoch (2 million to 15,000 years old) and the Holocene Epoch (up to approximately 15,000 years old). In The Netherlands no primary clay deposits are found, i.e. all clay is secondary, i.e. formed elsewhere and transported by wind, ice or water. 

Epoch Usually, the smallest division of geologic time. Periods are divided into epochs. The Holocene epoch ranges from the end of the last glaciation about 11 500 years ago to the present. 

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