Antarctic Drilling Program

 

Date of this Version

2007

Comments

Citation: Wilson, G. S., Levy, R. H., Browne, G., Dunbar, N., Florindo, F., Henrys, S., Graham, I., McIntosh, W. C., McKay, R., Naish, T., Ohneiser, C., Powell, R. D., Ross, J., Sagnotti, L., Scherer, R. P., Sjunneskog, C., Strong, C. P., Taviani, M., Winter, D. M., and ANDRILL McMurdo Ice Shelf Project Science Team (2007), Preliminary chronostratigraphy for the upper 700 m (late Miocene – Pleistocene) of the AND-1B drillcore recovered from beneath the McMurdo Ice Shelf, Antarctica, in Antarctica: A Keystone in a Changing World– Online Proceedings of the 10th ISAES X, edited by A.K. Cooper and C. R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 092, 4 p.

Abstract

Chronostratigraphic data available for the preliminary age model for the upper 700 m for the AND-1B drill core include diatom biostratigraphy, magnetostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr ages on calcareous fossil material, and surfaces of erosion identified from physical appearance and facies relationships recognized in the AND-1B drill core. The available age data allow a relatively well-constrained age model to be constructed for the upper 700 m of the drill core. Available diatom biostratigraphic constraints and 40Ar/39Ar ages allow a unique correlation of ~70% of the AND-1B magnetic polarity stratigraphy with the Geomagnetic Polarity Time Scale (GPTS). Unique correlation is not possible in several coarse diamictite intervals with closely spaced glacial surfaces of erosion and sparse microflora. However, the age model indicates relatively rapid (up to 1m / k.y.) and continuous accumulation of intervening finer grained diatomaceous intervals punctuated by several half to million year hiatuses representing more than half of the last 7 m.y. in the AND-1B record. The mid-late Pleistocene is represented by superimposed diamictite units separated from upper Pliocene alternating diamictites / diatomites by a ~ 1 m.y. hiatus co-incident with a regionally correlated seismic reflection surface. A c. 100 m thick diatomite represents a significant portion of the early Pliocene record in the AND-1B drillcore. Strata below ~620 m are late Miocene in age, however biostratigraphic constraints are absent below 586 m and correlation with the GPTS is relatively unconstrained.

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