Stratigraphy of the Soils of the Glacial Outwash, York County, Maine1

KENNETH V. GoooMAN2

FOR a long time soils have been mapped on glacialoutwash deposits. These deposits are found in all

parts of New England and other glaciated portions ofthe country. This paper deals particularly with thosein York County, Maine. The deposits there are exten-sive and frequent sand and gravel pits are found inthem which facilitate the taking of pictures for illus-trations. York County occupies the southern tip ofMaine and a soil survey of it was made during thesummer seasons of 1936 to 1938.

In general, glacial outwash is detrital materialswept out, sorted, and deposited beyond the glacialice front by meltwater streams. It may be in the formof plains, deltas, kames, valley trains, eskers, or lessergeological forms.3 The great bulk of the deposits,however, can be generalized into two groups, viz./(i) smooth outwash, which is usually nearly level togently . rolling ; and (2) rough outwash, which isstrongly rolling to hilly or steep. These generalnatural landscape characteristics have been observedfrequently by other workers iand have been regardedas major characteristics for the separation of certainsoil series, for example', the Hinckley and Merrimacsoils. It so happens, however, that in addition >tothe differences in topography, the deposits in YorkCounty have striking differences in the arrangement'or stratigraphy of their respective constituent ma-terials.

Possibly the most striking feature in the 'stratigra-phy of the outwash materials is the size of the sepa-rates. They range from a silt particle barely ahundredth of an inch in diameter to boulders 48to 60 inches in diameter. Most of the materials alsohave rather definite relationships between the sizesof the separates and the form of the deposits. Thehuge, nearly level plains and deltas, for example, areprimarily of sand which may have some silt varvesand scattered pebbles less than y2 inch in diameter.The narrow, irregular, winding eskers, on the otherhand, generally have a heterogenous mixture of cob-blestones and gravel with very little sand and ab-solutely no silt or clay varves. Of particular interestin York County are the sandy plains around Shap-leigh which have a pronounced rolling topography.In one place these plains have resulted from iceblock pits. These sandy plains are particularly inter-esting because the rolling relief is more usually as-sociated with coarser materials.

In addition to the range in sizes of the separates,a striking difference in the colors of the depositsoccur in York County. In the deposits derived prin-cipally from granite, gray, yellow, and brown colors

predominate, while in the deposits derived principal-.ly from schist, bright reddish yellows and reddishbrowns are prominent. Most of the sand and graveldeposits in the county are at least 20 feet deep, restusually on till' or rock ledges, but extensive areasnear the southern and northeastern parts are under-lain by clay. All of the deposits can be identifiedwithin three major groups, when only the sand andgravel are considered, and are arranged as- follows inorder of coarsest to' finest materials.

Group I.—The first group occurs most often onrather rough topography, such as eskers, crevassefillings, and valley trains. The slopes rarely are lessthan 1$% in gradient and are frequently 30 to 40%.It must be emphasized, however, that similar de-posits may occur on nearly level relief where stonyor cobbly fans have formed. The topography is notthe deciding characteristic. Instead, the differentiat-ing characteristics are the coarseness of the materialand its heterogeneity in mixture. Subdivisions with-in this group are based on whether the materials arederived principally from schist or from granite. Thematerial as a whole is most often a heterogenousmixture of coarse gravel, boulders, and sand (Fig. i).

The boulders and large separates are from 6 to 40inches in diameter and form the coarse skeleton ofthe mass. The gravel which fills the coarse skeletonis usually 2 to 4 inches in diameter and ranges fromy2 inch pebbles to the larger separates. Sand alsooccurs in this deposit, but it is less pronounced, as arule, than in the outwash of the following two groups.

Group II.—The second group has a broader rangein relief than the first, but again, is dependent largelyon the size of the separates, their arrangement, andorigin rather than topography for its classification.The second group most often occurs with a level togently undulating topography, having slopes of lessthan 10%, and appears predominately as glacial riv-er terraces. It may also occur as kames, eskers, andterrace escarpments with slopes of 30 to 50%. Thisgroup, unlike the first, has more gravel than bouldersor cobblestones in its deposits and about equal quan-tities of sand. The material is usually bedded orsorted in alternate bands of sand and gravel (Fig. 2).

The gravel of the coarse skeleton is usually muchfiner than in group I and is never larger than 3 or 4inches in diameter except in a few areas transitionalto the coarser group already mentioned. The sepa-rates filling the coarse skeleton are usually sands orcoarse sands and are rarely larger than. 0.1 or 0.2inch. Finer sands will occur, but in York County atleast, no silt or clay was observed in the glacial de-

Contribution from Division of Soil Survey Bureau of Plant Industry ,|Soils, 'and Agricultural Engineering, U; S. Dept, ofAgriculture.2Soil Scientist.

'Adapted from definition prepared by Inspectors Committee on Definitions of Coarse Fragments in Soils, Glacial Materials,and Land Forms, June 28, 1945. Mimeographed. '

452

GOODMAN: STRATIGRAPHY OF SOILS OP GLACIAL OUTWASH 453

presumably they are the sites of former ice blocksaround which the deposit is laid (Fig. 3).

The deposits of glacial outwash in group III arecomposed of nearly all sand,' have no cobblestones orboulders, and very little gravel which usually occursas scattered pebbles or as thin laminae rather thanthick layers or bands (Fig. 4). Some gravel in areas

. transitional to the coarser deposits naturally occur,but in general this group ranges from very fine tocoarse sand. The deposits may be heterogenous mix-tures of sand with occasional bands of finer silt orvery fine sand,'or they may be definitely banded intoalternate layers of fine or coarse sand, and in a fewinstances, very fine gravel. As with the first two, thethird and last group is also sub-divided into primarilygranitic or schistose deposits.

In York County, the classification of the soils de-veloped on the outwash is based on these threegroups. During the start of the survey the stratigra-

FIG. i.—Outwash deposit of group I, primarily bouldersand gravel; very little bedding or fine separates.

posits of group II. The bedding of the principal ter-race areas in York County is horizontal or nearlyso, but it may also be cross bedded. The importantdifferentiating characteristics to remember for groupII are that it is composed principally of gravel andsand and that it is usually sorted and bedded. Thisgroup is also sub-divided into principally graniticand-principally schistose materials.

Group III.—The third group has the finest materi-al of all and is frequently similar to both the first andthe second in topography. It usually occurs as deltas,outwash plains, or kame fields, but it may also occuras terraces. The relief usually ranges from level toundulating except in part of the sandy plains men-tioned before. On that portion known as "pitted out-wash" the relief is strongly rolling and is unusual onpredominantly sandy deposits. The pits occur in agenerally flat and nearly level deposit of sand and

FIG. 2.—Outwash deposit of group II, primarily sand andgravel; usually bedded and includes very few boulders.

454 SOIL SCIENCE SOCIETY PROCEEDINGS 1946

steep lands of other formations. The textures, how-ever, are nearly everywhere less coarse than in groupI and are usually sandy loams, gravelly sandy loams,or gravelly loamy sands. These represent most of theMerrimac and similar soils as well as the deposits ofgroup II (Fig. 6). In correlation, however, thisgroup was split into the Hinckley and Merrimac soilsprimarily because of differences in relief.

The soils in group III are composed primarily ofsands and occur almost equally on level and rollingrelief. In all cases observed, however, the deposits arewithout gravel except for a few scattered pebbles orthin bands of fine gravel. The textures are consistently^finer than either groups I or II and are usually loamysands, fine sands, or fine sandy loam. In correlation,the flat areas of this group were included with Col-ton (podzolized analogue of Merrimac) and Merri-mac, and the rolling areas with the Hinckley andsimilar soils. This split in the classification of soils on

FIG. 3.—Outwash deposit of group III, primarily sand; mayor may not be bedded and includes very little gravel.

phy was given first consideration and the slopes weremapped incidentally. As time went on, it became'ap-parent that nearly all the rough outwash havingstrongly rolling or steep slopes was also composed ofthe coarsest material as in group I. The textures arelargely gravelly, cobbly, or cobbly-stony loamy sands.The stony classification, however, in light of recentSoil Survey inspector's committee reports, shouldhave been "bouldery". In correlation, the few smallareas of coarse material with less, steep slopes werecombined with the rolling or steep areas. The surfaceof one such area is shown in Fig. 5. This representsmost of the Hinckley and similar soils as well as theoutwash of group I.

The remaining two groups in York County weremore troublesome. In general, the soils in group II,composed of 'predominantly gravel and sand, arecharacterized by a rather definite bedding and sort-ing of materials. .They 'occur most frequently on levelto undulating or sometimes gently rolling river andglacial terraces, but they also occur on rolling and

FIG. 4.—Outwash deposit of group III, primarily fine sand;may or may not be bedded and includes silt and clay varves.

GOODMAN: STRATIGRAPHY OF SOILS OF GLACIAL OUTWASH 455

are already classified on the basis of stratigraphy, andsince this is more in line with modern soil science, itseems unnecessary to combine Hinckley and Merri-mac or similar soils simply because certain areas arenearly alike. Instead, it seems more logical to re-define the series on the basis of the morphology ofthe soil profile and the stratigraphy ^of the glacialoutwash.

Based on the classical concept of a soil series asmentioned in Doctor Marbut's lectures, eight pointsof differences are involved in the profiles, as follows:

1. The numbers of the horizons2. The color3. The texture4. The structure5. The relative arrangement6. The chemical composition7. The thickness of the horizons8. The geology of the soil material

FIG. 5.—Hinckley gravelly loamy sand, showingsurface condition.

these deposits because of topography seems unneces-sary ; for the depth and uniformity of the predomi-nantly sandy materials within the soils indicates thatthey should have been classified neither Hinckley orMerrimac. In fact, where the deposits of this natureoverlay clay, as they do in the southern and north-eastern parts of the county, they are classified as theAdams soils.

It seems from the evidence that soils developedon glacial outwash need to be more clearly defined.It appears that to establish one series having a rangein parent materials equal to all three of the outwashgroups is illogical. Yet, there have been suggestionsmade to combine Hinckley and Merrimac, .the ma-terials of which include just such a range. These soilsas mapped in the past may grade into each other insome areas, and in a few may be alike, but this hasmore than likely been caused by the use of topog-raphy or the relief as a basis of differentiation insteadof the stratigraphy. Since some soils on the outwash

FIG. 6.—Merrimac sandy loam; limited amount of gravelin surface.

45<5 SOIL SCIENCE SOCIETY PROCEEDINGS 1946

FIG. 7.—Berwick loamy sand. -Note iron-cemented layernear bottom of spade.

The last item has been discussed and, according tothis as well as the remaining criteria, three or more,soil series.could be established in the major glacialoutwash groups.

For example, item I, the number of horizons, rare-ly exceed six or seven for the soils developed onthe bouldery deposits of group I. Usually two orthree surface layers, one or two B' horizons, and thenthe mixed very coarse materials of the C layer areall that occur to a depth of 5 or 6 feet. The numberof layers, particularly in the C horizon, are doubledor trebled in the bedded and sorted materials of groupII. The number stays about- the same as in group Ior is sometimes less in the sandy deposits of groupIII when the materials" are somewhat uniform.

The color of the horizons in all groups reflect morenearly the lithology of the deposits than the stratig-raphy. The color, however, is in part a differentiatingcharacteristic for soils developed on outwash groups

having the same stratigraphy. For example, theHinckley soils on the bouldery material -of group Iare differentiated from Jaffery on similar texturedmaterial because of differences in color due to thegranite or schist from which the deposits are derived.

The surface textures of the bouldery deposits ingroup I and the gravelly deposits of group II some-times grade into each other, but they are nearly al-ways distinct from the fine textures in the deposits ofgroup III. In group I the textures nearly always aregravelly, cobbly, or bouldery loamy sands, while ingroup II gravelly loamy sand, loamy sand, or sandyloam are more frequent. In group III the texturesrarely are coarser than a loamy sand or sandy loamand are most frequently loamy fine sand or fine sandyloam. Gravel'in any quantity does not usually appearin the upper horizons. In addition, silt and clayvarves are common' in the sandy deposits of groupIII but have not been observed in the coarser materi-als of groups I and II.

The structure of the horizons is not greatly differ-ent in any of the groups since most are single-grainedor structureless. The exceptions occur in the crumbstructure of the surface layers, and in group IIIwhere a weak platy structure occurs, in places, inthe silt and clay varves that occasionally appear atdepths below 4 or 5 feet (Fig. 4).

The relative arrangement of the horizons in thebouldery and coarse deposits of group I is usuallydifficult to determine. Coarse material usually occursthroughout the horizons of the deposit and distinctlayers are difficult to see. The exact reverse is usual-ly true with the bedded and sorted gravelly and sandy .layers in group II. In fact, there is usually a 15- or18-inch layer, including A and B horizons that is onlymoderately gravelly and may be comparatively gravelfree (Fig. 6). Below this are the well-defined alter-nate bands of sand and gravel which extend to aconsiderable depth and are of various thicknesses.The horizons in group III are usually arranged withthe coarser sands on the top of the deposits, 'the finermaterials below, but in a few places interbedded fineand coarse sands — not gravel — have also been ob-served (Fig. 3). - .

The chemical composition of the horizons, like thecolor, is less a function of stratigraphy than is thelithology of the rocks from which the deposits arederived. High iron ratios exist in the soils developedover deposits of schistose materials. This is so definitein York County that an iron-cemented layer 2 to 6inches thick frequently occurs within the finer out-wash deposits of groups II and III derived fromschistose materials (Fig. 7, near the bottom of thespade). Like the color of the horizons, the chemicalcomposition is a differentiating characteristic for soilsdeveloped on deposits with similar stratigraphy. Itis an important distinction between Merrimac andBerwick soils, both occurring on deposits in groupsII or III.

The thickness of the horizons is a major criteriafor differentiation between soils on the bouldery de-posits of group I, the gravelly and sandy material of

GOODMAN: STRATIGRAPHY OF SOILS OF GLACIAL OUTWASH 457

group II, and the sandy or fine sands of group III.Very few surface horizons on the coarse materialsexceed a total of 5 or 6 inches in thickness and arerarely thicker than 10 or 12 inches to the hetero-genous mixture of cobblestones and boulders in theC layer. On the bedded and sorted gravel and sanddeposits of group II, however, A horizons having atotal thickness of 10 or 12 inches are frequent, andincluding the B, the horizons are often 20 to 24inches deep to the banded sand and' gravel C layers.The A and B layers on the sandy deposits of groupill are also 20 to 24 inches or more deep, but theboundary between'the B and C layers is never sodefinite as in the spils on the deposits of group II.

Based on the foregoing criteria, the soils mappedon the coarsest material as in group I should be clas-sified as Hinckley, if granitic; Jaffery, if schistose inorigin. Soils on the moderately coarse sand and grav-el as in group II should be classified as Merrimac, ifgranitic; Berwick if schistose in origin. Soils on thefinest, predominantly sandy materials, as in groupIII, should be classified as Adams or some similarsoil. Other soils occurring in the same general groupsin other parts of the country are Danby, Otisville, andEtna on the rough outwash and coarse materials ofgroup I; Colton, Stetson, and Chicopee on the grav-el and sandy materials of group II; and Agawamand Adams on the deep sandy deposits of group III.These soils reflect differences in morphology andparent materials other than those mentioned. Someare podzolized, some are limy, and some are de-veloped from materials other than granite or schist.All of them can be differentiated on the basis' of thestratigraphy and the profile characteristics even

though certain topographic and geological forms aresimilar.

On nearly all the glacial outwash in York Countythe relationships between stratigraphy and plant lifereflect more the coarseness of the material involvedand its arrangement than any particular kind of ma-terial. Dense 'stands of white pine growing to enor-mous heights have been reported on the soils of thesandy plains around Shapleigh. Thin stands of pineand aspen are common on the gravelly and boulderyeskers, crevasse fillings, or deltas; while mixed standsof oak, pine, and maple seem to occur more frequentlyon soils of the terrace deposits with bedded and sortedgravel and sand. The relationships between crops andthe stratigraphy are best illustrated on a few soiltypes occurring on the sands and gravel of group IIand the sands of group III. Cultivated fields do notoccur on group I soils. Most of the Merrimac andBerwick sandy loams occurring on the bedded andsorted sand and gravel of group II give fairly goodyields of vegetables and potatoes when properly fer-tilized and limed. Some fields of Colton and Adamsfine sandy loams occurring on the sandy deposits ofgroup III seem to be more drouth resistant than anyof the other soils developed on outwash except theshallower fine sandy loams underlain by clay. Al-though these soils underlain by clay are classified ina separate group as Melrose and Suffield fine sandyloams and were not included in the general discus-sion, they bear out the inference that soils on thefiner sandy deposits have a greater moisture-holdingcapacity and are more fertile than those on theHinckley and similar soils underlain by coarse rubbleand gravel.