A sedimentary paleomagnetic record of the Matuyama chron from the Western Antarctic margin (ODP Site 1101)

A high-resolution paleomagnetic record for part of the Matuyama chron (0.7- 2.1 Ma) is reported for Ocean Drilling Program Site 1101 (Leg 178), off the Antarctic Peninsula Pacific margin. A rock-magnetic investigation of 62 di screte samples revealed that the natural remanent magnetization (NRM) is ca rried by pseudo-single domain magnetite. Progressive alternating field dema gnetization of 83 in of U-channels provided a polarity stratigraphy down to the Olduvai subchron. Two geomagnetic events preceding the Jaramillo subch ron were identified, including the Cobb Mountain polarity interval. The bul k magnetic parameters vary by more than a factor of 20 over the entire time interval, but by less than a factor of 6 over the 0.7-1.1 Ma interval. Thi s latter interval was selected for paleointensity determinations, which wer e carried out by normalizing the NRM by the anhysteretic remanent magnetiza tion (ARM). Direct comparison of the Site 1101 paleointensity record with o ther curves available for the same time interval suggests a geomagnetic ori gin for features present in the record. A more quantitative comparison was achieved by means of a jackknife test performed on nine records of relative paleointensity over the 0.95-1.1 Ma interval. This test yielded no outlier for the period considered, confirming the geomagnetic character of the rec ords. We have constructed a low-resolution stack revealing some of the char acteristic paleointensity features of the Jaramillo subchron. (C) 2001 Else vier Science B.V. All rights reserved.