At least 17 times during the past 1.7 million years, the deposition of loess containing characteristic cold-resistant gastropods was interrupted by the development of temperate interglacial forests. This conclusion was reached in a study of paleomagnetically dated fossiliferous loess sequences in Krems, Austria and Brno, Czechoslovakia. Sequences of windblown loess interlayered with hillwash loams and steppe and forest soils exposed in brickyards around Brno and Praha, Czechoslovakia, revealed eight major depositional cycles within the Brunhes paleomagnetic epoch. We now report nine additional cycles of late and middle Matuyama age bringing the total number of glacial-interglacial cycles to 17, which occurred after the end of the Olduvai. The cycles are separated by marklines, levels of abrupt environmental change correlative with the terminations in deep-sea sediments. They are the boundaries between the windblown loess containing cold-resistant snail assemblages and between the clayey originally decalcified soils, accompanied by warmth loving Helix and Banatica snail faunas of hardwood forests. Because the presence of temperate forests in northwestern and central Europe is instrumental in the definition of an interglacial, each markline represents a glacial-interglacial boundary and each cycle is a glacial-interglacial cycle.

Paleomagnetic measurements have been carried out on 103 specimens taken at about 15 cm intervals in a sea cliff exposing the marine terrace formation. Secondary components were removed by partial demagnetization in a peak field of 200 Oe. Two short reversed magnetozones are recognized. Geological and biostratigraphical evidence indicates that they are equivalent to the Blake event, which was first reported by Smith and Foster (1969) (Science 163 , 565–567) from the North Atlantic deep-sea cores. The present result suggests a split nature for the Blake Event.

Evidence is presented for a more extensive ice cover over South Georgia, the South Orkney Islands, the South Shetland Islands, and the tip of the Antarctic Peninsula. Ice extended across the adjacent submarine shelves to a depth of 200 m below present sea level. Troughs cut into the submarine shelves by ice streams or outlet glaciers and ice-scoured features on the shelf areas suggest that the ice caps were warm-based. The South Shetland Islands appear not to have been overrun by continental ice. Geomorphological evidence in two island groups suggests that the maximum ice cover, which was responsible for the bulk of glacial erosion, predates at least one full glaciation. Subsequently there was a marine interval and then a glaciation which overran all of the lowlying peninsulas. The Falkland Islands, only 2° of latitude north of South Georgia, were never covered by an ice cap and supported only a few slightly enlarged cirque glaciers. This suggests that the major oceanographic and atmospheric boundary represented by the Antarctic Convergence, which is presently situated between the Falkland Islands and South Georgia, has remained in a similar position throughout the glacial age. Its position is probably bathymetrically controlled.

At the San Joaquin plant site near Bakersfield, California, the Brunhes/Matuyama reversal was identified 4 m below an ash probably correlative with the Bishop Tuff. Deposition of coarse detritus in a high-energy environment preceded the reversal, whereas a low-energy lake and back-swamp type sedimentation persisted through most of the interval, separating the reversal and the ash. Sediments below the reversal are strongly remagnetized in a normal field. Identification of the original polarity is possible only with some of the specimens, so that accurate positioning of the reversal plane required dense and multiple sampling. Similar precaution at all sites where reversals are used for time-stratigraphic correlations is recommended. Paleomagnetic investigation was particularly useful in proving the presence of unfaulted strata at least 0.5 my old, as required by safety regulations of the U.S. Nuclear Regulatory Commission (NRC). This is due to the fact that any thick layer of reversely magnetized sediment is with high probability older than 0.7 my.

Postglacial and lacustrine sediments from Lake Michigan have been paleomagnetically investigated. The primary goal was to test the feasibility of correlation between several cores in terms of their magnetic signatures. After alternating field and thermal demagnetizations, inclination and relative declination values were obtained that show characteristic short-term fluctuations. Major features, including changes in the magnetic intensity of the samples, correlate well in three of the longer cores, in good agreement with independent lithostratigraphic determinations. In addition, we have been able to detect local disconformities that appear as interruptions of the magnetic record. A continuous record of normal polarity has been found, extending from the present day to 13,000 14C vears BP. No reversals were recorded, though at two stratigraphic levels shallow inclinations, together with declination swings and low intensities of magnetization, may indicate rapid geomagnetic excursions. The magnetic record was attained at the time of deposition or shortly thereafter, and can be used for a wide range of applications.

The Gothenburg Magnetic Excursion in a broad sense ranges from 13,750 to 12,350 years BP and ends with the Gothenburg Magnetic Flip at 12,400−12,350 years BP (= the Fjärås Stadial in southern Scandinavia) with an equatorial VGP position in the central Pacific. The Gothenburg Magnetic Flip is recorded in five closely dated and mutually correlated cores in Sweden. In all five cores, the inclination is completely reversed in the layer representing the Fjärås Stadial dated at 12,400−12,350 years BP. The cores were taken 160 km apart and represent both marine and lacustrine environments. The Gothenburg Magnetic Flip represents the shortest excursion and the most rapid polar change known at present. It is also hitherto the far best-dated paleomagnetic event. The Gothenburg Magnetic Excursion and Flip are proposed as a standard magnetostatigraphic unit.