Richard Foster Flint

Growth of North American Ice Sheet During the Wisconsin Age

The evidence of separate Labradorian and Keewatin centers of radial glacial flow is confined almost wholly to very late Wisconsin time, and indicates that these centers shifted their positions widely even during that short time. There is no evidence that these centers ever were the sites of independent glaciers; their importance has been overemphasized. The North American ice sheet, during the Wisconsin maximum, was recognized as a single mass and named the Laurentide ice sheet before the names Labradorian and Keewatin were applied. The Laurentide ice sheet is believed to have originated as mountain glaciers chiefly in the conspicuous highlands of eastern Quebec, Labrador, and Baffin Island. Nourished by moist maritime air masses derived mainly from the south and southeast and moving northward and eastward, these glaciers coalesced into, piedmont glaciers. By continued growth southward and westward toward the principal sources of their nourishment, the piedmonts thickened and spread, burying the highlands in which they had originated. Ultimately they formed a vast ice sheet that extended from the east coast to the Cordillera. Further eastward expansion was prevented by the deep water of the Atlantic, in which the ice broke up and floated away. Glacial-anticyclonic winds are assumed to have been subordinate to cyclonic storms in nourishing the ice sheet. The Labradorian, Keewatin, and other centers of outflow recorded by striae were broad low domes on the surface of the ice and were caused by exceptional concentrations of snowfall. While the ice sheet was shrinking, these domes shifted position.

PLEISTOCENE CLIMATES IN EASTERN AND SOUTHERN AFRICA

Pleistocene climates in the southern half of Africa are indicated by evidence of lakes in regions now dry, ancient soils for whose development the climate is now too dry or too wet, inactive wind-blown sand now covered by vegetation, and signs of former glaciation. Such features indicate climates different from those now prevailing. In addition, anomalies in the distribution of living organisms seem to support the assumption of climatic change. Most of the evidence indicates change in annual amount or seasonal distribution of rainfall, but some suggests former temperatures lower, possibly by as much as 5°C., than those of today. Few of the features discussed are well fixed stratigraphically, but most of them are probably late Pleistocene. The atmospheric-circulation pattern shows that annual amount and seasonal distribution of rainfall differ markedly in various regions in the subcontinent. The current literature contains a start toward a reconstruction of former patterns which are compatible with the geologic and biogeographic evidence, based on analogies with modern anomalies. Although probable, the theory that pluvial climates in Africa were contemporaneous with glacial climates in Europe remains unsupported by geologic evidence, mainly because data are very few.

Quaternary glaciations and environments of northern Isla Chiloé, Chile

Author9s Note. I should like to preface this paper with a few remarks, as the work of Richard Foster Flint, who died in June 1976, was a major key to interpreting the Quaternary of Isla Chiloe. Fortunately, he was well along on preparing a map of the glacial deposits, and the geological substance of this paper is drawn from this map and the careful and systematic notes he took in the field. Our field time was during January and February 1976. For Richard Foster Flint, the study was looked upon as an opportunity to relate the glacial events that he and Francisco Fidalgo described at the same latitude on the east side of the Andes in Argentina. For me, the study was a rare sequel to previous studies of Quaternary stratigraphic palynology in southern Chile. The lowland of northern Isla Chiloe was glaciated by piedmont glaciers of Andean origin. Three offlapping layers of drift are, respectively, thoroughly weathered (Fuerte San Antonio), partly weathered (Intermediate), and fresh (Llanquihue). The coldest climatic regime, shown by the stratigraphic palynology, prevailed when the Fuerte San Antonio drift was deposited. The Intermediate drift dates from at least 57,000 yr B.P. and the Llanquihue from at least 43,000 yr B.P.

Glacial Geology of the East Flank of the Argentine Andes between Latitude 39°10′S. and Latitude 41°20′S

The segment of the Argentine Andes between lat. 39°10′ S. and lat. 41°20′ S. was glaciated extensively and repeatedly during the late Pleistocene; today only a few small glaciers at high altitudes are present. The former glacier consisted of an ice sheet, in places more than 1500 m thick, centered on the high Cordillera. At times the ice divide may have shifted westward, away from the present water divide, in the direction from which the glacier was principally nourished. The ice sheet separated into lobes that occupied the valleys of major east-flowing streams. The distance between the high Cordillera and the terminus of the longest lobe is about 70 km. Cirque altitudes form an orderly sequence, rising eastward in the direction of increasing temperature and aridity in today9s climate. Three bodies of glacial drift were identified: Pichileufu, El Condor, and Nahuel Huapi, in order of decreasing age and extent. Possibly the Nahuel Huapi Drift consists of two members. Small bodies of drift younger than the Nahuel Huapi Drift were not studied. Isotopic dating has not been possible because no datable substances in, or significantly related to, the drifts were found. Comparison of the progress of weathering of granitic clasts in the zones of weathering in the drift bodies suggests that the intervals between the times of drift deposition were not long. None of the drift is believed to be older than the Wisconsin Drift in North America. The data in hand do not permit closer comparison.

Pleistocene Sand Ridges and Pans in Western Rhodesia

Long, wide, but extremely low, parallel ridges of sand are believed to represent the eroded stumps of former longitudinal dunes. Lacking erosion channels of any kind, they are probably unique features. The former dunes are thought to have been degraded mainly by sheet erosion, which was effected by (1) a high-intensity rainfall, (2) a partial vegetation cover, and (3) an unconsolidated, permeable sandy terrain. Probably this combination of factors is rare. Small basins in the troughs between the sand ridges are underlain by a mixture of sand and clay that came from the ridges. These basins are maintained by deflation, together with excavation by buffalo, elephant, and other large animals. The history of the ridges implies Pleistocene climatic change. A very wet period succeeded a very dry period. Also a short, recent dry period is suggested.

Glacial Drift in the Eastern Argentine Andes between Latitude 41° 10' S. and Latitude 43° 10' S

The segment of the Argentine Andes between lat 41°109 S. and lat 43°109 S. was formerly occupied by a thick mountain ice sheet, which in places spread as far east as long 71° W. The eastern limit of glaciation determined by us is broadly similar to that fixed by Caldenius in 1932, although it differs in detail. We have separated the glacial drift in the area into three units, defined on a semiquantitative basis of degree of weathering of granitic clasts. This three-fold sequence contrasts with a sequenceof four units proposed by Caldenius. The intensity of weathering of our two older units is considerable. It seems to us too great to be compatible with the dates implied by Caldenius9 correlation with drift, in Sweden, dated according to the time scale of De Geer. However, the weathering displayed by the drift in the Argentine area could reasonably have developed within a time interval no longer than that generally ascribed to the Wisconsin Age (in the wide sense) in North America, although the oldest drift could conceivably be pre-Wisconsin.

PROBABLE WISCONSIN SUBSTAGES AND LATE-WISCONSIN EVENTS IN NORTHEASTERN UNITED STATES AND SOUTHEASTERN CANADA

A variety of evidence suggests that the borders of the Cary and Mankato drift sheets cross eastern New York and New England, that there were two and perhaps three late Wisconsin marine invasions of the St. Lawrence lowland, and that there exist logical eastern correlatives of the low-water phases in the glacial upper Great Lakes, in the form of till-covered marine deposits, the abandoned, drift-filled Niagara gorge, and the North Bay-Ottawa River lake-outlet channel. The suggested events from the Gary maximum to the present are assembled in a correlation chart for comparison and criticism. Although the scheme proposed is suggestive only, it is consistent with ecology implied by fossils, with the dates and amplitudes of known crustal movements, and with the radium- and radiocarbon dates of the dated materials collected from the region.

Origin of the Cheney-Palouse scabland tract, Washington

SCOPE OF STUDY The remarkable system of abandoned valleys and channels trenched into the basalt of the Columbia Plateau in eastern Washington has long attracted attention. I have had opportunity to examine many parts of this system during three seasons’ study of the drift border and glacial features at the northern margin of the plateau. During that time it gradually became apparent that the published explanations of the genesis of these drainage ways did not meet the requirements of the field data as I saw them, and, accordingly, a fourth season (summer, 1936) was devoted to an intensive examination of one of the principal drainage tracts of the complex. The results of the study are offered herewith, in the hope that the additional data presented may lead toward a more general agreement than was possible before, on the cause and character of the streams that formerly flowed across the plateau. . . .

Late Quaternary changes of level in western and southern Newfoundland

Emerged Quaternary marine features are numerous along the west coast of Newfoundland, although their distribution is patchy. They include wave-cut benches and cliffs, localized constructional forms such as beach ridges, bars, and deltas, and a discontinuous blanket of fossil-bearing marine sediments. These features reach progressively higher elevations toward the north; their positions in long east-west bays indicate a westerly component in the northward rise. The highest marine limit is very indistinctly recorded, but a lower strand line, cutting the latest glacial deposits, and rising northwestward, is well marked by wave-cut benches on weak rocks. Strand lines in intermediate positions are very weak, but wave-cut benches are well developed at present sea level. These facts indicate upwarping following deglaciation, the movement having been interrupted by one long pause and followed by another pause at present sea level. No unequivocal evidence of emergence was found along the western half of the south coast, although emergence may be recorded farther east. The northwestward rise of the marine features along the west coast is consistent with (though it does not prove) the hypothesis that part or all of Newfoundland was invaded by the Labrador ice sheet during the latest (presumably Wisconsin) glacial age and that the warping was caused principally by unloading of the crust by the Labrador ice sheet during the same glacial age. Evidence in two districts on the west coast indicates that at least part of the postglacial eustatic rise of sea level occurred while glacier ice was still actively present, and prior to at least part of the crustal warping.

Glacial features of the southern Okanogan region

INTRODUCTION That part of eastern Washington which lies between the Cascade Range, on the west, and the high Rockies, on the east, carries an extensive record of Pleistocene glaciation. The belt drained by the west-flowing segment of the Columbia River is of special significance because in it was localized the southern margin of glacier ice during at least two successive glaciations. The great terraces of stratified drift and the striking channels, dominated by the Grand Coulee, that are associated with these ice borders, have attracted interest since the first scientific exploration of the region. The present paper, in discussing the chief glacial features in the lower Okanogan trench and in the district extending east up the Columbia River from the mouth of the Okanogan, aims at a rational explanation of the relations between these features. REGIONAL SETTING Northeastern Washington consists of a rugged highland, underlain chiefly by pre-Tertiary resistant rocks, . . .