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SUMMARY:Preservation of very old climate records in ice cores from Allan H
 ills\, Antarctica - Edward Brook\, Oregon State University 
DTSTART:20240423T111000Z
DTEND:20240423T120000Z
UID:TALK215347@talks.cam.ac.uk
CONTACT:Dr Rachael Rhodes
DESCRIPTION:Extending the ice core record of climate and environmental par
 ameters to time periods older than 800\,000 years is a major international
  goal. The Center for Oldest Ice Exploration (COLDEX) is a US initiative t
 o search for climate records covering the last 5 million years\, including
  cores from blue ice regions where very old ice has been identified. This 
 talk will discuss recent COLDEX results from one of these areas\, the Alla
 n Hills\, in the Transantarctic Mountains region of East Antarctica. Ice c
 ores from the Allan Hills contain discontinuous sections that date to as o
 ld as 6 Ma\, and numerous samples with ages between 1 and 5 Ma\, all dated
  with the 40Aratm technique. These samples provide constraints on a variet
 y of past environmental variables\, including greenhouse gases\, mean ocea
 n temperature\, and Antarctic surface temperature\, and create opportuniti
 es to explore other properties of climate and the environment beyond the 8
 00 ka limit of the existing ice core record.  \n\nThe Allan Hills cores an
 d their glaciological setting are also unusual and complex\, requiring new
  approaches to their interpretation. Ice flow\, likely from a relatively l
 ocal depositional area\, traps old ice at shallow depths near the ice marg
 in\, albeit in a poorly understood manner.  In most locations drilled so f
 ar\, ice younger than 1 Ma is underlain by a relatively thin layer (20-40 
 m) of older material. Dating Allan Hills cores clearly shows age reversals
  indicative of folding. Deformation of dust and tephra bands at the surfac
 e\, and deformation of bubbles at depth\, also indicate complex ice flow. 
 Three-dimensional mapping of electrical conductivity and isotopic measurem
 ents in large\, 24-cm diameter cores clearly shows inclined layers and fol
 ding. Work to decipher these complex records is ongoing. \n
LOCATION:Department of Earth Sciences\, Tilley Lecture Theatre
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