Exercise 2 relative and absolute dating of geologic events answers


11-Nov-2017 05:53

P.; bog pollen records of rapid and drastic vegetation changes in Isla Santa Inés (Chile); eolian soil record from Hólmsá (Iceland); North Atlantic benthic core in ODP site 980; dendrochronological records from Irish and Lancashire oaks with some of their narrowest rings during the 3,195 BC decade; Ötzi, the ice-man from South-Tyrol; core S53 palynological record from Burullus Lagoon (Nile Delta); Soreq Cave (Israel) speleothem; Mauritanian coast core 658C; Kilimanjaro ice-core record; Awafi dry lake sediments in SE Arabia; Lake Mirabad sediment in the Zagros Mountains (Iran); Lunkaransar dry lake sediments in NW India; sedimentary section along the Hongshui River, in the southern Tengger Desert, NW China. Since they constitute dramatically different climatic states, the nature of abrupt climatic changes is also different in the two states.

Glacial variability comes mainly in the form of warming episodes (Dansgaard-Oeschger events; figure 45) while interglacial variability comes from cooling episodes (Bond events; figure 45).

It has become a lot more difficult to identify these changes because their signal is much lower and more difficult to separate from the noise of small high frequency climatic variability.

This has created much confusion about the nature and causes of Holocene abrupt climatic changes and has given many the false impression that the Holocene is characterized by long periods of climate stability. The Holocene is a period of almost constant climate change with climatic stability being the exception. Nature of climatic oscillations during the Ice Age.

Evidence for abrupt cooling (blue), aridity (red), flooding (green) and high wind (purple). The main difference between both states is in the redistribution and minimal or maximal exploitation of that energy by the planet.

South-Cascade Glacier rooted tree-trunk (Washington State); remains and artifacts in the Little Salt Spring (Florida); Cariaco Basin metal concentration (Fe, Ti) in ODP site 1002; Quelccaya Glacier ice-buried wetland plant (Juncaceae), dated at 5,138 ± 45 yr B. This is due to the orbital configuration, tectonic disposition, ice and cloud albedo, oceanic-atmosphere response and biological feedback.

12 belonging to the Northern Hemisphere are represented in brown, 4 from the Southern Hemisphere in blue, and one for the Low Latitudes in yellow.

Notice that all Holocene abrupt climate changes are cooling events. Grey bars, cooling oscillations part of the ~2400 year Bray cycle.

Glacier growth was caused by orbital-driven insolation changes.

Although variability in local conditions caused the Neoglacial to start at different times in different glaciological areas, it is generally agreed that it started between 6000-5000 years BP in both hemispheres.

There are no global warming abrupt changes in the Holocene once the thermal maximum is reached, just cooling events followed by recovery.

The other major salient characteristic of the Holocene abrupt climatic changes compared to glacial abrupt changes is their much smaller amplitude (figure 45).

Orange and grey downward bars represent significant volcanic and cold events respectively according to the references indicated.