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Hardpan Soils of the Coastal Plain of Southern Maryland

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Hardpan Soils of the Coastal Plain of Southern Maryland Hardpan Soils of the Coastal Plain of Southern Maryland GEOLOGICAL SURVEY PROFESSIONAL PAPER 267-B Hardpan Soils of the Coastal Plain of Southern Maryland By C. C. NIKIFOROFF GEOLOGY AND SOILS OF THE BRANDYWINE AREA, MARYLAND GEOLOGICAL SURVEY PROFESSIONAL PAPER 267-B A study of reconstruction oj the environment in which soilformation took place UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955 UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 15 cents (paper cover) CONTENTS Page Page Abstract.._ _______________________________ 45 The hardpan soils of the Brandywine area. _. 52 Introduction .-_____-_-_-__-_________.___._ 45 General morphology of Beltsville soil.... 52 Theoretical basis__-_--.--_----_----_-___.__ 46 Red mottling of the subsoil-___________ 53 The hardpan.__________-_---___----- 56 Parent material— __-__-_-__--_____-__ 46 Hypotheses about the origin of hardpan. 57 Inherited and acquired soil characteristics. 48 Soils without hardpan.________________ 59 Paleopedology _ _ _______________________ 49 Conclusion.._____________--__--_----.-_-. 61 Buried and fossil soils_--_----_-_______- 50 Literature cited.__________-___---_-___---. 62 Soil evolution.___-._---___-__-______._ 51 Index._ _____-_-__--_---.---------------. 63 ILLUSTRATIONS FIGURE 35. Profile along Sunset Trail. 57 TABLES TABLE 1. Mechanical composition of Beltsville and Chillum fine sandy loams.. _______ 62 2. Mechanical composition of Beltsville silt loam and Chillum loamy fine sand. 62 in GEOLOGY AND SOILS OF THE BRANDYWINE AREA, MARYLAND HARDPAN SOILS OF THE COASTAL PLAIN OF SOUTHERN MARYLAND By C. C. NIKIFOROFF* ABSTRACT Field data suggest that the hardpan may have been inherited by the present soils from the earlier stages of development Soil, a function of the environment, is a natural combination which, presumably, took place under a periglacial climate. of parent material, landform, climate, and biotic factors. The These stages should have been antedated by still earlier stages, concept of the parent material is vague, but this material is during which the initial parent material was affected by lateri­ the source of virtually all inherited soil characteristics. Its zation. It is suggested that laterization could have taken place alteration by atmospheric and biotic agencies imparts to the during the Sangamon interglacial stage and hardpan develop­ soil a series of new or acquired characteristics. Generally, ac­ ment during the Wisconsin stage. quired characteristics are not fixed and are subject to changes by the environment. Some of these characteristics, however, INTRODUCTION are irreversible and upon being acquired are retained by the soil irrespective of environment. Thus, certain properties which The original objectives of this study were to reex- were imparted to the soil during the earlier stages of evolution amine some peculiar characteristics of hardpan soils on may be retained throughout the later stages, during which they the Coastal Plain to determine if the earlier stages of would not develop anew. Evolution of soils consists of changes in the geographical pattern of distribution of different soils, development were indicated and to allow reconstruction rather than development of new forms or species. An area of the environment in which soil formation took place. occupied now by certain soils may have been occupied by dif­ Some tentative suggestions on these subjects were made ferent soils in the past and may be occupied by still others in the in a previous publication (Nikiforoff, Humbert, and future. The study of past stages of soil evolution is the field of Cady, 1948). However, the study is a problem not only paleopedology. In polygenetic soils the new characteristics are superimposed upon the remnants, of irreversible old features. for the soil scientist but also for the geologist. In some places, however, old soils are buried under younger The soils in question are developed from stratified deposits so that more recent soils develop above the ancient. Coastal Plain sediments which greatly complicate Soils that retain some features of the past stages of their analysis of genetic profiles. These profiles are super­ evolution and buried soils might serve as valuable stratigraphic imposed upon the lithologic units, the genesis and markers. stratigraphy of which are not yet fully understood. A Soils of the Beltsville series in eastern Maryland are charac­ terized by an uncemented hardpan ranging in thickness from correct interpretation of these profiles, therefore, seems about 1 foot to more than 3 feet and covered by a mantle of problematic until the pertinent geology can be clarified. mellow loamy material. This loamy layer consists largely of Hence, a detailed geologic survey of a quadrangle was silt. These soils are developed from the upper loamy member made and the problem studied jointly by a geologist of the Brandywine formation. In most places the material underlying the hardpan is marked by red mottling, the pattern and a soil scientist. of which indicates that mottling has been acquired after the Geologists, geomorphologists, and other specialists deposition of sediments. Red mottling is suggestive of lateriza- who visited the area showed considerable interest in tion. The present soils of the region are not lateritic. Appar­ the project. About 50 members of the Geological So­ ently this mottling was imparted to the soils during one of the ciety of America spent the greater part of a day in earlier stages of evolution in which climatic conditions may have been conducive to laterization. the area on a field trip preceding the 1950 annual A conspicuous feature of the hardpan in Beltsville soils is meetings. In the spring of 1951 the Friends of Pleisto­ the polygonal vertical cleavage resembling the pattern of large- cene held their annual convention in the same area. scale mud cracks. The soils with such a hardpan occupy the Among other visitors, were the late Kirk Bryan who undissected remnants of the upland deposits. Three hypotheses offered valuable suggestions; C. B. Hunt who is now of the origin of the present hardpan are discussed, and the working on a similar problem; L. L. Ray with a group soils are compared with the associated soils lacking hardpans. of his coworkers; C. S. Denny, L. C. Peltier, L. Leopold, *D. S. Department of Agriculture, Soil Conservation Service. W. Armstrong-Price, and others. 45 46 GEOLOGY AND SOILS OF THE BRANDYWINE AREA, MARYLAND The interest shown by so many specialists is en­ Usually, soil parent materials are thought to be the couraging and much appreciated. Discussions in the unconsolidated products of the weathering of rocks, field and by correspondence are being continued. The whether hard or mellow. Hence, the soil's parent ma­ study now seems to be centered on problems of a more terial cannot be identified with loose mantlerock. Like general character. Therefore, a short review of the any other rock, the mantle, if it consists of transported theoretical basis for the analysis of these problems sediments and has a great thickness, is merely a source might be in order. This review forms the major part of the parent material of the soil. Only that part of the of the paper, and although no positive answer to the mantle which is directly affected by weathering in place, cardinal question has yet been found, some new data for example, the upper 10 to 20 feet, serves as parent on the original subject are given. material. Deeper portions of the mantle may or may not be similar to the top layer and may be altered by THEORETICAL BASIS other deep-seated processes which do not affect the top PARENT MATERIAL layer. Development of soil represents alteration of the man­ Neither is hard rock a parent material. In some tle rock by atmospheric and biotic agencies. Usually places a soil might develop from solid rock which soil is defined as a product of alteration of the so-called may appear to be a parent of the thin residual soil. "parent material" by environmental agencies. The Such cases, however, are exceptions and it may be word "product" in this definition, however, is objec­ argued that the rock should have been rendered loose tionable because it connotes a certain finality. After before the beginning of its transformation into an em­ becoming an entity, the product, as commonly under­ bryonic soil. Although the parent material—which is stood, is no longer dependent upon the process by which neither the initial rock nor the resultant soil but merely it has been brought into being. Earlier, and perhaps a stage of the process—is not represented now by any more correctly soil has been defined as a function of part of the present soil profile, it should have been rep­ environmental factors, rather than a product of their resented in the past, when the rock was pulverized but interactions (Dokuchaev, 1899). Function is defined had not yet become a soil. The state of such a material by Webster as a "quality, trait or fact so related to an­ during this stage of weathering is not well understood. other (fact or facts) that it is dependent upon and The inherent weakness of this theoretical concept, as varies with that other." Hence, a function is an entity a certain stage in the gradual decay of rocks, is that it only as long as the factors on which it depends continue presupposes some elusive boundary between two differ­ to operate. Function changes when the factors which ent processes, or between two different stages of one bring it into existence are altered. The phrase "func­ continuous process—formation of the parent material tion of the environment" describes the essence of soil and the transformation of this material into soil.
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