SEMINAR: MGG Student Seminar *TODAY!! Tuesday Noon 2/12* Arash Sharifi

[Alan Piggot <apiggot@rsmas.miami.edu>]

MGG STUDENT SEMINAR

TUESDAY, FEBRUARY 12

12:00 - 1:00 PM

CIMAS CONFERENCE ROOM, 3RD FLOOR

The Zen Way of Geochemistry

Utilizing biomarkers to study the Holocene climate variability of West Asia

Arash Sharifi

 

Chemical biological markers or "biomarkers" are molecular fossils that originated from formerly living organisms. Their complex organic compounds are mainly composed of carbon, hydrogen, and oxygen with possible contribution of other elements. They can be found in sediments, rocks, and crude oils and show little or no change in structure from their parent organic molecules in living organisms. Compare to other organic compounds, the complex structure of biomarkers can reveal more information about their biotic sources and the environmental conditions, which the parent organisms may experienced. This study is an attempt to utilize different organic biomarkers to reconstruct the Holocene climate variability over West Asia using peat records from an ombrotrophic (rain fed) peat complex in NW Iran.

Neor pet mire is located around the tectonic lake in NW Iran without any known riverine or ground water input.  Located at the elevation of 2700 meter above the sea level, Neor considered as one of the high-elevated lakes in Iran, which receives its water solely from annual snow and rainfall and hence can reflect the changes in atmospheric precipitation and dust input.  Radiocarbon dating on 24 samples from a 775-cm peat core  show a nearly constant rate of accumulation (1.7 mm yr^-1, R2=0.99) since 13356 ± 116 cal yr B.P.  The results of this study demonstrate a significant correlation between the abundance of emerging plants with high P_wax values and the episodes of intensive atmospheric dust deposition with high Ti intensities.  The opposite correlation is also true for high P_aq values of submerging plant and low atmospheric dust input.  The existing correlations indicate that the deposition of dust over the West Asia took place during warm and dry periods.  Since 5000 BP, the major warm and dry episodes, inferred from our data, are in good agreement with the historical and archeological records of drought, famine, socio-economical changes, and cultural transitions over Persian planes, Mesopotamia, and eastern Mediterranean.  Preliminary wavelet analysis of inorganic and organic proxies reveals that the Holocene millennial and sub-millennial variabilities are composed of at least five periodicities.  Our results strongly suggest that the wavelets correspond to 512 and 220-year cycles are directly forced by solar activity.