Quaternary Glacial Periods Research Articles

Miocene history of the Benguela Current and Antarctic ice volumes: Evidence from rhythmic sedimentation and current growth across the Walvis Ridge (Deep Sea Drilling Project Sites 362 and 532)

The history of the northward growth and of the fluctuations of the Benguela Current from the middle Miocene (ca. 14 Ma) to the uppermost late Miocene (ca. 5 Ma) has been reconstructed from analyses of the coarse and clay fractions and geochemical analyses of the organic matter in sediments from Deep Sea Drilling Project Sites 362 and 532. In the middle Miocene the Benguela Current had not yet reached the Walvis Ridge, and consequently, no local upwelling occurred. Carbonate preservation was good during this period of low productivity. Rhythmic changes related to Antarctic ice volumes were weak, leading to slightly higher organic matter concentrations and higher montmorillonite/illite (M/I) ratios in sediments deposited during times of greater continental ice. Montmorillonite was carried north from the Orange River by the Benguela Current, whereas illite originated from the nearby Namib Desert. In the early late Miocene the Benguela Current reached the Walvis Ridge in colder periods and led to well‐developed rhythmic increases in opal, which was transported from near‐coastal upwelling areas. Organic matter concentration, carbonate dissolution, and M/I ratios were also enhanced during periods of greater ice volume. During the late Miocene, farther northward migration of the Benguela Current led to a change in the uppermost Miocene sediments: opal contents and M/I ratios were high during times of low ice volume rather than in colder times. During the cold periods, local winds from the Namib desert increased the illite supply to the Walvis Ridge and depressed the M/I ratio. In these periods, the Benguela Current flowed farther to the north, reaching the Angola Basin as it did in Quaternary glacial periods. Throughout these changes, sediment organic carbon content was always enhanced in high‐ice‐volume periods from near‐bottom downslope transport of organic matter from shelf regions during regressions, and carbonate dissolution in the sediments was increased as a result of oxidation of this organic matter.

Die Bedeutung der pleistozänen Vogelfaunen der Höhlen im Ungarischen Mittelgebirge

In the present study, the fossil bird fauna of the caves of the Hungarian Middle Mountains is examined for evidence in support of the hypothesis that the Carpathian Basin may have served as a faunal refugee during the last Quaternary glacial period. As an introduction, the reasons for the refugee hypothesis, including paleobotanical and glacial theoretical aspects, are discussed. Since the first bird fossils of the cave fauna considered in this paper belong to the Würm I-II, the faunistic conditions of the Riss glacial period are not discussed in detail, The known faunas up to the Würm II are interstadial, which seems to serve only as indirect support for the refugee hypothesis. Paleobotanical evidence, both for and against the hypothesis, is also considered. In conclusion, the abundant cave faunas of all phases of the Würm III are cited as being - at least at the present time - the most convincing argument for the refugee hypothesis. The heterogeneous composition of these faunas permits certain tentative conclusions regarding the faunas of Würm I and II.

Klimazeugen des periglazialen Dauerfrostbodens in Mittel- und Westeuropa: Ein Beitrag zur Rekonstruktion des Klimas der Glaziale des quartären Eiszeitalters

Abstract. Certain periglacial phenomena (ice-wedges, cryoturbations, patterned ground, pingos) are critically investigated with respect to their outer appearance as well as to the causes of their formation, but especially how far they might be used as indicators of an old permafrost. The results for Central and Western Europe have been mapped according to our actual status of knowledge. The attempts hitherto made to reconstruct the climate of the Quaternary glacial periods, have been thoroughly checked. A new calculation of the maximum diminution of Pleistocene temperature gives a value of 15—16° C (bottom temperature) in Central and Western Europe. For the Younger Dryas we still have to expect a temperature depression of 11—12° C. Both values have been found by comparing mean annual temperatures in the border-zone of permafrost at the high-glacial time and during the Younger Dryas with the actual temperatures. This is true on the premise that the active permafrost area can be limited by the — 2° C annual isotherme, both under actual as well as under glacial climatic conditions.

Glacial Epochs of the Santa Monica Mountains, California

Summary The Santa Monica Mountains of southern California are far too low to have been glaciated, but the features of their south-facing coast are believed to record four epochs of sea rise and abrasional advance alternating with three epochs of sea lowering and withdrawal during intermittent coastal upheaval; and these seven epochs of high and low sea level are interpreted as representing the last four Nonglacial Epochs (including the present Postglacial) and the last three Glacial Epochs of the Quaternary Glacial Period. Acknowledgments The following pages present the results gained in company with a number of my friends on twenty or more visits to a 30-mile stretch of the Southern Californian coast during the last six years. Various aspects of the problems there encountered have been profitably discussed on the ground with Prof. J. E. Wolff, my former colleague at Harvard University, now resident in Pasadena; with my former student, . . .

Glacial Epochs of the Santa Monica Mountains, California

Summary The Santa Monica Mountains of southern California are far too low to have been glaciated, but the features of their south-facing coast are believed to record four epochs of sea rise and abrasional advance alternating with three epochs of sea lowering and withdrawal during intermittent coastal upheaval; and these seven epochs of high and low sea level are interpreted as representing the last four Nonglacial Epochs (including the present Postglacial) and the last three Glacial Epochs of the Quaternary Glacial Period. Acknowledgments The following pages present the results gained in company with a number of my friends on twenty or more visits to a 30-mile stretch of the Southern Californian coast during the last six years. Various aspects of the problems there encountered have been profitably discussed on the ground with Prof. J. E. Wolff, my former colleague at Harvard University, now resident in Pasadena; with my former student, . . .

Some Biological Problems comected with the Himalaya

Summary.(1) The Himalaya underwent a period of uplift from sea‐level commencing in Eocene times and reached their present approximate elevation in Pliocene times. The Quaternary Glacial Period caused intense cold on the Himalayas and Tibetan Plateau, but precipitation was insufficient to form an extensive ice‐cap.(2) Modern distribution in the Himalaya and Indian Peninsula were not much influenced by the Quaternary Glacial Period.(3) Discontinuous distribution is evidence of previous continuous distribution, intervening extermination being brought about by some form of competition.(4) The afforested area of the Himalaya from Kashmir to Bhutan, and up to timber‐line, is a sub‐region of the Oriental Region and not of the Palæarctic Region. It was colonised almost entirely from the east or the hills of western China.(5) The Tibetan Plateau is definitely a sub‐region of the Palmirctic Region, and was probably colonised from the north.(6) The Kashmir sub‐region is probably more correctly placed in the Palæarctic than the Oriental Region, and appears to have been colonised from the north or north‐west.(7) A Transition Zone above timber‐line forms a true contact zone between the Palæarctic and Oriental Regions along the Himalayan Divide from Kashmir to Bhutan and beyond.

Tidal Friction and Ice Ages

A CAREFUL study of the conditions of land height during the earlier stages of the Quaternary glacial period seems to show that the earth was then less oblate, i.e. the north and south polar regions stood higher than now, to the extent of as much as 10,000 ft. in places, while the equatorial regions stood lower, by some 500 ft. The spreading of ice-sheets from these high lands may well have been the initial cause of the cooling which produced the Glacial epoch.