Sundar Raj
Manager (Geology) Mineral Exploration Corporation Limited, Nagpur, Maharashtra
Wednesday, August 17, 2022
Tuesday, August 20, 2013
Friday, January 04, 2013
Guide to terminology used in paleoclimate studies of the last 150,000 years
“Event”,
Stages
|
Estimated
age (Calendar years)
|
Holocene
|
~10 Kyr to
Present
|
Holocene
maximum warming (also referred to as “climatic optimum”)
|
~4.5 to 6
Kyr (
|
Last
deglaciation
|
~18 to 10
Kyr
|
Termination
I
|
~14 Kyr
|
Younger
drayas
|
~12.7 to
11.5 Kyr
|
Antarctic
cold reversal
|
14 to 13
Kyr
|
Bolling-Allerod
warm period
|
14.5 to 13
Kyr
|
Last
Glacial
|
~74 to 14
Kyr
|
LGM (Last
Glacial Maximum)
|
~25 to 18
Kyr
|
Last interglacial
peak
|
~124 Kyr
|
Termination
II
|
~130 Kyr
|
Eemian/MIS
Stage 5e
|
~128 to
118 Kyr
|
Heinrich
events
|
Peaks of
ice-rafted detritus in marine sediments, ~7 to 10 Kyr time scale.
|
Dansgaard-Oeschger
events
|
Warm-cold
oscillations determined from ice cores with duration ~2 to 3 Kyr
|
Bond
Cycles
|
A
quasi-cycle during the last Ice age whose period is equal to the time between
successive Heinrich events.
|
Terminations
|
Periods of
rapid deglaciations
|
Thursday, October 11, 2012
Principle sources of paleoclimatic proxies
Studies of past climates must begin
with an understanding of the types of proxy data available and the methods used
in their analysis. One must be aware of the difficulties associated with each
method used and of the assumptions each entails. With such a background, it may
then be possible to synthesize different lines of evidence into a comprehensive
picture of former climatic fluctuations, and to test hypotheses about the
causes of climatic change.
Major types of proxy data available
is given below; (Bradley. R.S., 1991)
1.1.
Glaciological (Ice cores):
A.
geochemistry
(major ions and isotopes of oxygen and hydrogen)
B.
gas
content in air bubbles
C.
trace
element and micro particle concentrations
D.
physical
properties (e.g., ice fabric)
1.2.
Geological:
A.
Marine
(ocean sediment cores)
(i) Biogenic sediments (planktonic and benthic
fossils)
(a) Oxygen isotopic composition
(b) Faunal and floral abundance
(c) Morphological variations
(d) Alkenones (from diatoms)
(ii) Inorganic sediments
(a) Terrestrial (Aeolian) dust and ice-rafted debris
(b) Clay mineralogy
B.
Terrestrial
(a) Glacial deposits and features of glacial erosion
(b) Periglacial features
(c) Shorelines (Eustatic and glacio-eustatic features)
(d) Aeolian deposits (loess and sand dunes)
(e) Lacustrine sediments, and erosional features (shorelines)
(f) Pedological features (relict soils)
(g) Speleothems (age and stable isotope composition)
1.3.
Biological:
A.
Tree rings
(width, density, stable isotope composition)
B.
Pollen
(type, relative abundance, and/or absolute concentration)
C.
Plant
macrofossils (age and distribution)
D.
Insects
(assemblage characteristics)
E.
Corals
(geochemistry)
F.
Diatoms,
ostracods, and other biota in lake sediments (assemblages, abundance, and/or
geochemistry)
G.
Modern
population distribution (refugia and relict populations of plants and animals)
1.4.
Historical
A.
Written
records of environmental indicators (para-meteorological phenomena)
B.
Phenological
records
Reference:
1. Bradley, R.S. and Eddy, J.A. (1991). Records of
past global changes. In: Global Changes of the Past (R.S. Bradley, ed.).
Boulder: University Corporation for Atmospheric Research, pg. 5-9.
Saturday, August 04, 2012
Tuesday, January 24, 2012
Wednesday, November 10, 2010
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