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The Journal of Geology | 1948

Physiographic divisions of Illinois

Morris M. Leighton; George E. Ekblaw; Leland Horberg

The classification proposes minor modifications in Fennemans divisions and recognizes subdivisions of the Till Plains and Great Lakes sections, based largely on glacial features. The boundaries and characteristic features of the subdivisions are described, and their origin and relations to glacial features and bedrock topography are discussed.


The Journal of Geology | 1960

The Classification of the Wisconsin Glacial Stage of North Central United States

Morris M. Leighton

The Wisconsin glacial stage is classified on the basis of stratigraphy into six glacial substages, named, from older to younger, Farmdale, Iowan, Tazewell, Cary, Mankato, and Valders. In this paper names are proposed for the intraglacial substages not previously designated, completing the sequence as follows: These divisions fit the natural succession and provide the basis for historical and climatic interpretations of a broad scope, be they glacial advances, pauses, retreats, stagnation, eustatic changes of sea level, events beyond the ice sheet, changes of biotas, climatic changes and climatic controls, and analysis of radiocarbon dating. Valley trains were deposited during active maximum and submaximum stands of the glaciers and were in part followed by glacial torrents. The latter occurred when the icecap was being reduced and sea level was being raised. Except in the case of the Valders, another refrigeration followed, but the climatic change that halted the advance of the Valders was revolutionary. It brought on progressive stagnation and initiated the Recent about 11,000 radiocarbon years ago. This paper also gives consideration to other classifications including the one recently proposed by Frye and Willmans new classification.


The Journal of Geology | 1961

Illinoian Glaciation in Illinois

Morris M. Leighton; John A. Brophy

Present knowledge of the Illinoian glaciation in Illinois supports the following interpretations: (1) the invading Illinoian glacier was one of great vigor; (2) its limit was determined by a change in its climatic controls which halted its advance and initiated the retreat of its margin, during which moderately thick submarginal drift was deposited but no continuous terminal moraine or recessional moraines were built; (3) northeast-southwest trending ridges of the Kaskaskia River basin are stagnation features, recording the fact that the glacial margin had retreated little more than 25 miles before the glacier became stagnant; (4) many crevasse fillings were made and after some crevasses, both longitudinal and frontal, had reached through the ice, eroding streams confined along them cut straight shallow depressions, some of them crossing divides and forming trellis drainage; (5) numerous beautiful conical and ellipsoidal moulin kames, some compound and mammoth in bulk, were made helter-skelter along and between crevasse fillings as the glacial ice became decadent; (6) the small Mendon recessional moraine on the higher Galesburg Plain north of Illinois River records a somewhat longer glacial activity for a brief time, but its construction was soon followed by stagnancy when crevasse traces were eroded on flat surfaces back of it, causing many of the present linear lines of drainage; (7) the Buffalo Hart Moraine, continuous north of Illinois River for but little more than 60 miles records a brief time of renewed snowfall and glacial activity; (8) the Illinoian Glacial Lobe at its maximum development had the full deployment suggested by Leverett as covering northwestern Illinois at the time that it reached southeastern Iowa and its maximum limit in southern Illinois; (9) the dominant dolo-mitic bedrock of the northern counties and the greater relief of the region provided conditions for different physical and geochemical weathering than those of the coal measures area to the south; (10) the glacier was as vigorous when it transgressed the northern area as it was elsewhere, and it became stagnant when the rest of the glacial lobe became stagnant; (11) during the Sangamon interglacial interval, weathering and erosion modiaed the Illinoian drift everywhere, the profiles of weathering assuming characteristics according to the physical and chemical conditions; (12) no loess was deposited anywhere on the Illinoian drift because there were no valley trains during the wasting-away of the glacier, the glacier melting down in place; (13) the only loess deposit genetically connected with the Illinoian glaciation is the pro-Illinoian Loveland loess that is found over wide areas beneath and beyond the Illinoian drift; (14) Farmdale loess and the superjacent Peorian loess (Iowan and Tazewell) form a widespread mantle over the weathered Illinoian and other deposits of much of the midwest.


Geological Society of America Bulletin | 1933

Eldoran Epoch of the Pleistocene Period

George F. Kay; Morris M. Leighton

Recent Classification of the Pleistocene Period In a recent paper, Kay[1][1] proposed the following classification of the Pleistocene period (system)[2][2] of the Mississippi Valley: In discussing this classification, it was pointed out[3][3] that “When the most significant facts of Pleistocene history are analyzed critically in relation to what might be considered as a logical classification it is evident that from the time of the advance of the first ice sheet, the Nebraskan, to the retreat of the last ice sheet, the Wisconsin, there were recurrences of similar geological events with accompanying similar geological results. In other words, there were within the limits of the Pleistocene period a succession of cycles, the most significant evidences of which are recorded in the deposits which were made during each cycle and in the changes which the deposits underwent before the coming of the succeeding cycle. Reasons were given for the interpretation that . . . [1]: #fn-1 [2]: #fn-2 [3]: #fn-3


The Journal of Geology | 1931

The Peorian Loess and the Classification of the Glacial Drift Sheets of the Mississippi Valley

Morris M. Leighton

The Peorian has always been regarded as the shortest interglacial stage of the glacial epoch. Now it appears from recent new evidence that the Peorian stage was geologically too brief to be regarded as an interglacial stage. Calcareous Peorian loess in the Iowan drift area rests on calcareous Iowan drift, and in Illinois the early Wisconsin ice buried the Peorian loess before it was weathered. Peorian time is recorded primarily by the loess deposit, and the time was so short that we are forced to regard the Iowan ice invasion as the first of the series of invasions of the Wisconsin glacial epoch. This permits, on the one hand, a natural classification of the Wisconsin stage, according to ice centers, and, on the other, a subdivision of Pleistocene time in America that harmonizes with the subdivisions of Europe.


The Journal of Geology | 1958

Important Elements in the Classification of the Wisconsin Glacial Stage

Morris M. Leighton

The Wisconsin glacial deposits in the classic area of the Upper Mississippi Valley have long been important in the classification of the last glacial stage. A review of these elements, including recent findings, is made to weigh better some views that have arisen during the past few years. Labradorean or Patrician Iowan and Farmdale drifts have been differentiated in northern Illinois west of the border of the Tazewell substage. Northeastern Illinois is classic for the Patrician and Labradorean Tazewell and for the Patrician Cary. The Mankato and Valders drifts of the Patrician field lie to the north and northeast, but their lacustrine equivalents are recognized in the Lake Chicago area, as are the terrace remnants and backwater silts from the Keewatin field along the Mississippi River and its tributaries. Thus there occur in Illinois many of the facies of all the Wisconsin glacial substages. Their correlation and integration into the history of the last glaciation afford the proper basis for their classification. Divisions of the Wisconsin glacial stage were not made until after the duality of the glacial epoch became known. Six glacial substages of the Wisconsin are now recognized, two of which-the first and the last- have been recently added. They now include the Farmdale, Iowan, Tazewell, Cary, Mankato, and Valders. The states of the Midwest have long been the classic area of the world for glacial studies of the Pleistocene by reason of their geographic extent, the striking deployment of the drift sheets, and the abundance of related phenomena that record a complex and varied history. A brief summary of the evolution of the classification is given not only to emphasize the growth of the science but to reveal the misdirection that is sometimes given to stratigraphic studies and interpretations by errors of classification. An attempt is also made to show that advances in glaciological knowledge illumine the observations that one makes today and give impetus to further studies and that, as new techniques are developed, the glacial geologist finds his responsibilities for the older disciplines increased. Thus sound classifications that come from well-directed inquiries give expression to and are in harmony with the natural history of the Pleistocene, our ultimate goal.


The Journal of Geology | 1959

Stagnancy of the Illinoian Glacial Lobe East of the Illinois and Mississippi Rivers

Morris M. Leighton

The hitherto unrecognized features of Leveretts ridged drift of the Kaskaskia Basin throughout its course from the Shelbyville moraine in south central Illinois nearly to Belleville in southwestern Illinois; its genetic crevasse ridges, subcrevasse channels on the land surface, and moulin kames; together with sparse but wide distribution of similar features over the greater part of the Illinoian drift area east of Illinois and Mississippi rivers attest to the stagnant condition of the Illinoian glacial lobe for this region after it had reached its terminus and made its marginal deposits.


The Journal of Geology | 1958

Principles and Viewpoints in Formulating the Stratigraphic Classifications of the Pleistocene

Morris M. Leighton

The criticisms and views expressed in the recently circulated preliminary report of the Pleistocene committee of the American Commission on Stratigraphic Nomenclature on the present stratigraphic system of classification of the Quaternary suggest some lack of familiarity with the classic area of the Middle West. The multiple classification that the committee recommends, excellent as it may be for the older rocks, is not compatible with the nature of the glacial Pleistocene. The classification for the older rocks is the natural result of acquiring an understanding of them, just as the present classification of the glacial Pleistocene has evolved from decades of investigation. The classic area of the glacial Pleistocene comprises all of the type areas for the known glacial and interglacial stages of North America. So influential were the climates on most geologic processes, even in the depths of the ocean, that correlations with the glacial and interglacial stages of the Pleistocene are sought from all quarters. It is therefore important that the system of stratigraphic classification for the glacial Pleistocene shall be one that is naturally adapted to it rather than one that applies to marine strata. The non-glacial Pleistocene, however, may well be susceptible to the latter.


The Journal of Geology | 1966

Farmdale Glaciation in Northern Illinois and Southern Wisconsin

Morris M. Leighton; John A. Brophy

The upper (Pecatonica) drift of the Pecatonica River basin and adjacent areas of northern Illinois and southern Wisconsin is believed to offer the best record in North America of a late Farmdale substage, Wisconsin stage of glaciation. The thinness of the drift and lack of end moraines, coupled with glacially deformed bedrock, indicate a brief but intensive glaciation by a glacial lobe moving from the North Bay, Ontario, area across Rock River and westward against the drainage of Pecatonica basin. Evidence favoring assignment of the Pecatonica drift to the Farmdale substage include: (1) its areal position beyond the outer margins of the Labradorean Iowan, Tazewell, and Cary drift sheets, (2) its strati-graphic position just above deeply weathered Illinoian drift, (3) a paleoregosol locally preserved in the upper part of the drift where it lies beneath Iowan loess, (4) the fact that the Farmdale loess which is widespread beyond the Pecatonica drift border has not been found either above or below the Pecatonica drift (thus indicating contemporaneous deposition), and (5) radiocarbon age of from 29,000 to about 31,000 B.P.


The Journal of Geology | 1934

Evaluation of Boundaries in the Mapping of Glaciated Areas

Morris M. Leighton; William E. Powers

Little has been written concerning the field technique used in the detailed mapping of Pleistocene deposits and the relative values of the various types of boundaries thus established. In this paper the use of certain criteria in mapping the Wisconsin moraines of northeastern Illinois is described. A study of several types of glacial boundaries and the data on which they are based shows that these boundaries differ greatly in accuracy, depending in part on the inherent characteristics of the boundary and in part on the data available to and gathered by the field worker.

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John A. Brophy

North Dakota State University

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