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Agassiz Ice Core Readme

A note on the time scales for this series, from Holocene climate records from Agassiz ice cap, Ellesmere Island NWT, Canada. Fisher, Koerner, Reeh.
From 0 to 8000 BP the time scales are tied first to the A77 time scale (ie. Agassiz 1977 core) which was first dated by measuring about 20 segments of core at greater than 6 samples per year so as to be able to see annual variations in dust, and positive ion chemistry as well as liquid conductivity and PH. Then the A77 ECM record was put on this time scale and compared to that for Dye 3 and Camp Century (Greenland). The 8 major ECM peaks for A77 were also the major ones for Greenland within the errors in the initial time scale (about 10%). Then the A77 time scale was adjusted to put the major ECM peaks at the Dye 3 dates. This procedure works for A77 back to about 7000 BP, at which point the layer thicknesses are too small to take fine enough samples. The del-O18 end of the transition was set to the Dye 3 age, which at that time was thought to have been 10,700 BP. All the other Agassiz cores were tied into A77 using flow time scales adjusted so their ECM records best fitted the A77 major peaks. Hence all the Agassiz records are tied to Dye 3.
Now, the Dye 3 time scale in the early Holocene is thought to be wrong and the new Summit GRIP/GISP2 age for the transition is 11,550 BP instead of 10,700! So the Agassiz records should be pinned at this new transition date. This file is still just tied to the Dye 3 ages, which are probably OK in the 0-8000 BP range. In the 8000- transition range they should probably be streched so as to put the transition at 11,550 BP. In the figures you will notice that the x-axis time markers stop at 8000 BP and then there is only a 11,550 age at the delta 18 transition. If you find this time scale business a little variable and confusing you are not alone. Remember from 0-8000 its OK and from 8000- transition needs a little changing so transition=11,550 BP. At least all the cores are tied to each other.
David Fisher 7/22/94
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