The depth/age relationship for the GISP2 core has been developed from a
variety of core parameters, including: annual layer counting of visual
stratigraphy, electrical conductivity, laser light scattering of dust, stable
isotopes, major anions and cations, insoluble particles, 
Pb, total
beta activity, and 
C from occluded (from air trapped in the ice) CO
[e.g., Wilson and Donahue, 1990; Dibb, 1992; Taylor et
al., 1992; Alley et al., 1993; Meese et al., 1994a,b], plus ice
dynamics modeling [ Schott et al., 1992]. Current estimated age error is
2% for 0-11.64 kyr BP, 5% for 11.64-17.38 kyr BP, and 10% for 17.38-40.5
kyr BP [ Alley et al., 1993; Sowers et al., 1993; Meese et
al., 1994a]. While the age scale back to 40.5 kyr BP comes from a variety of
techniques [ Meese et al., 1994a], below 40 kyr BP the chronology comes
from correlating GISP2 with the Vostok chronology which Sowers et al.
[1993] derived using the 
O of O
[ Bender et al., 1994].
This approach to correlation invokes the fact that the 
O of
atmospheric O
varies with time but, at any one time, is constant throughout
the atmosphere.
As shown in Table 1, a variety of projects and a total of forty-two types of measurements comprised the GISP2 deep drilling effort as of the completion of drilling, and a total of nine additional projects provided direct information necessary to the interpretation of the resultant record (e.g., atmospheric sampling, automatic weather stations, surface glaciology, modeling). A general description of these activities has already been presented [ GISP2 Investigators, 1993; Mayewski et al., 1994a].
For purposes of this paper we will focus only on highlights of the environmental record thus far deduced.