lllll!nmn,!i ATE , G f°t ? lc *LsuRVE 3 3051 OOO05 339 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/sedimentdistribu67fras ;gn 67 ENVIRONMENTAL GEOLOGY NOTES MARCH 1974 • NUMBER 67 SEDIMENT DISTRIBUTION IN A BEACH RIDGE COMPLEX AND ITS APPLICATION TO ARTIFICIAL . BEACH REPLENISHMENT ^*V?& ^ ^ 9 Gordon S. Fraser and Norman C. Hester ILLINOIS STATE GEOLOGICAL SURVEY John C. Fry©, Chief • Urbana, IL 61801 SEDIMENT DISTRIBUTION IN A BEACH RIDGE COMPLEX AND ITS APPLICATION TO ARTIFICIAL BEACH REPLENISHMENT Gordon S. Fraser and Norman C. Hester ABSTRACT Severe erosion of much of the beach ridge complex along the Illinois shore of Lake Michigan east of Zion and Waukegan is taking place, especially in the northern half of the area. As much of the area is developed and oc- cupied, methods of restoring and preserving the shoreline are being sought. One proposed method involves replenishing the eroded shore, either by filling or feeding. If this method is used, two factors must be considered: (l) the material supplied should match that now found on the shore, and (2) the ma- terial must be available in sufficient quantities near by to make the project economically possible. A study of the beach ridge complex was made to determine the specific character of the sediments currently being deposited and the grain size of the materials deposited in the past when the complex was being formed. The sand body that forms the complex along the Illinois shore is approx- imately 7 miles long and 2.5 miles wide, including a subaqueous platform 1.5 miles wide, and it is as much as 35 feet thick. The subaqueous portion con- sists of an offshore segment of fine to very fine sand and a nearshore area (in water less than 15 feet deep) where sand and granules occur. The shore material ranges from medium-sized sand to pebbles. West of the shore, medium- sized sands are found in dunes and on eolian sand plains. Material similar to that currently being deposited on the shore is available within the complex in sufficient quantity for use in a replenish- ment program. The material was laid down on ancient shores as the sand body prograded south and east from the original shoreline. - 1 - - 2 - INTRODUCTION Large segments of the shorelines of the Great Lakes consist of Wiscon- sinan and Holocene sediments that are particularly prone to erosion, especially during periods of high lake level, because they are unconsolidated deposits. This natural process of erosion becomes a problem when it begins to affect shore areas that man has occupied. The Zion-Waukegan area along the Illinois shore of Lake Michigan, which was extensively eroded as a result of the 1952 high lake level, is again undergoing intensive erosion as a result of the recent rise in lake level. Because it is a highly developed area, methods to protect and re- store the shoreline are being sought. Common methods of protection against erosion have made use of man-made structures such as groins, sheet piling, and various types of armoring. Arti- ficial beach replenishment, including both beach feeding and beach filling, also have been used. These methods are discussed in a nontechnical report by the U.S. Army Corps of Engineers (1972). Geologic processes become important considerations when beach replen- ishment is selected to retard the erosion. First, how the shore and nearshore processes have acted in the past and how they are now affecting sediments must be understood before the future movement of sediment can be predicted. The be- havior of these processes in the Zion-Waukegan area has recently been discussed by Hester and Fraser (1973) . Second, the textural characteristics of the sediments on both the pres- ent and ancient shores must be known so that a sediment that has the proper grain- size characteristics can be selected to replenish the shoreline. Third, a source of usable sediment must be found in the immediate area to make the method economically feasible. Maps delineating the distribution of surface sediments (both subaerial and subaqueous) and subsurface sediments are therefore necessary. The results of an investigation of the texture of the sediments and of sediment distribution in the area are presented in this paper. This study is one of several investigations of Lake Michigan bottom sediments and shorelines being conducted by the Illinois State Geological Survey. A cknowl edgments We are grateful for the consideration and help we received during this research from many individuals. Eugene Carter, Joseph McCloskey, John Mihovil- ovich, Michael Morris, and Norman Sandelin of the Commonwealth Edison Company; George Fell and John Schwegman of the Illinois Nature Preserve Commission; John Comerio, Robert Corrigan, Phillip DeTurk, Helen Lyons, Robert Needham, and Donald Weathers of the Illinois Department of Conservation; Murray Pipkin of the Illinois Division of Water Resource Management; Phillip Fragassi of the Lake County Water District; Jerry Soesbee of the Lake County Park District; Donald Kramer of the Illinois Department of Transportation, District 1; Howard Peskator, Waukegan Water Company; James Cunningham of Soil Testing Service; Captain Richard Thibault and the crew of the R. V. Inland Seas; Carter Jenkins of Jenkins, Merchant - 3 - Mo, n Strut Camp Logan i?th Straat $h,lof* B'vo Loca ton Mop WIS. \ * MICHIGAN \ * Study Ario /o / £ I o J 9 ILLINOIS INDIANA Small Industry suJJ k Complex Fig. 1 - Physical and cultural features of the beach ridge complex along the south- western shore of Lake Michigan. Except for Illinois Beach State Park and the Nature Preserve, the area has been oc- cupied by man. (Modified from Hester and Praser, 1973. ) and Nankivil; and Julia Badal Graf, University of Illinois, were particu- larly helpful. Use of the R. V. Inland Seas was made possible "by the Great Lakes Research Division, Univer- sity of Michigan. CULTURAL AND PHYSICAL SETTING The shoreline east of Zion, Wau- kegan, and Winthrop Harbor, Illinois, is part of a beach ridge complex on the southwestern shore of Lake Michi- gan that extends from Kenosha, Wiscon- sin, to a position just east of Wau- kegan, Illinois (fig. l). Its sub- aerial portion is approximately ik miles long and ranges from essentially nothing just southeast of Kenosha to 1.1 miles vide in the area of the Il- linois Beach Nature Preserve. Only the portion south of the Illinois-Wiscon- sin boundary is considered in this re- port. The beach ridge complex is bounded on the east by Lake Michigan and on the west by a bluff composed of glacial material, mostly till. Except in Illinois Beach State Park and the Illinois Beach Nature Preserve, the complex, particularly along the shoreline, has been occupied by man. Most of the structures in the area are residences , but there are two areas of industrial development , one the Commonwealth Edison Company's nu- clear power plant east of Zion and the area to the west along Shiloh Boule- vard, and the other an extensive com- plex of factories and a fossil fuel power station east of Waukegan at the southern end of the beach ridge com- plex. The subaerial portion of the com- plex encompasses several major envi- ronments, including beach ridges cov- ered with trees and shrubs , dune rid- ges covered with shrubs and grass, marshes covered with reeds and grass, and the modern shore, which has little or no vegetation. - k - The complex in the area of the Illinois Beach State Park is charac- terized surficially by an orderly, linear or gently curving arrangement of beach and dune ridges. Relief be- tween the ridge and swale may be so slight, however, that the lineation can be recognized only by subtle changes in vegetative cover that are easily distinguishable on infra-red aerial photographs . North of the park the ridges are poorly defined and dis- continuous, the area consisting mainly of low- lying, hummocky sand plains and marshes. North of the Illinois-Wis- consin state line, the marshes are generally absent and the area is cov- ered by an eolian sand plain. Part of the beach ridge complex lies offshore as a broad apron of sand that slopes gently under the lake east and south of the subaerial portion. It thins toward deeper water and changes in texture with the addition of silt and clay. The complex is a transitory fea- ture that is now suffering extensive erosion, with associated permanent loss of land to the north and general accretion (with periods of temporary loss) of land to the south. The com- plex is migrating from north to south and has suffered several periods of extensive erosion (Hester and Fraser , 1973). The geologic record of the mi- gration and the erosion indicates that the same processes will no doubt con- tinue in the future. METHOD OF STUDY .Pig. 2 - Sites of the investigations con- ducted. Cross sections and fence dia- grams were constructed from drill hole data to provide a concept of the in- ternal structure of the beach ridge com- plex. (Modified from Hester and Fraser, 1973.) In an area consisting of 17 square miles (fig. 2), k6 holes were drilled in the subaerial portion of the beach ridge complex with the Illinois Geological Survey's Mobil B-30S, 27 holes were hand augered, 8 beach profiles were trenched, and 10 outcrops were excavated. Data from 128 drill holes were provided by Commonwealth Edison, the Illinois Department of Transportation, District 1, and Soil Testing Services. - 5 - Data from 30 holes in the subaqueous portion of the beach ridge com- plex, were provided by Commonwealth Edison, Soil Testing Services, and the Wau- kegan Water Company. Thirty-five additional holes were drilled through the sediment body and samples were taken with a jet airlift drill designed by Robert Woolsey of the University of Georgia's Marine Institute, Sapelo Island, Georgia, and constructed by the Illinois Geological Survey. Split-spoon samples from water depths of 15 to 35 feet that ranged from 1^ to 2 feet in length were col- lected at 30 sites. This drilling was done from the R. V. Inland Seas, which is operated by the University of Michigan Great Lakes Research Division under Na- tional Science Foundation sponsorship. Altogether, over 900 samples were col- lected by these various methods and were sieved in the laboratory at a sieve in- terval of 0.5 . Topographic maps , soil maps , and aerial photographs of the area were used to delineate geologic provinces and reconstruct the geomorphic development of the beach ridge complex (Hester and Fraser, 1973). ENVIRONMENTS OF DEPOSITION Hester and Fraser (1973) defined the major environments of the beach ridge system, but only those environments in which sand and/or gravel are the common sediments are discussed here. Dune, shore, nearshore, and offshore environments are included. The shore and nearshore environments extend east- ward to the outer slope of the permanent submarine bar, whereas the offshore environment extends lakeward from that bar. Each of these environments may con- tain sediments ranging in size from very fine sand to pebbles. Usually, how- ever, sediments of one or two size classes predominate, and these size classes are different for each of the environments where sand and/or gravel are being deposited (fig. 3). The shore environment is characterized by the presence of coarse sand, granules, and pebbles. Dune sediments, on the other hand, contain only medium and fine sand, whereas the offshore sediments are predominantly very fine sand, although a few samples may contain significant amounts of coarse sand and gran- ules. Sediments of the nearshore environment are highly varied, ranging in tex- ture from gravel to silt. In very few samples, however, is the material coarser than coarse sand. Nearshore sediments tend to have less medium sand than dune sediments but more medium sand than offshore sediments. Dune Environment Much of the subaerial portion of the beach ridge complex is covered by eolian sands. Dune ridges are well developed just west of the modern shoreline, especially in the southern portion of the complex, but they are less pronounced farther inland. In the northern part of the sand body, the ridges are discontin- uous, and many of them have coalesced to form an eolian sand plain. Where ex- tensive marshes are present in the western portion of the complex, dunes are gen- erally absent. - 6 - Grain size of the dune material varies only slightly from dune to dune throughout the area. However, grain size may vary considerably in any one dune. Sands in the lee of the dune are the coarsest and show the greatest vertical variability, whereas those of the foredune are finest and vary least vertically. Sand from the dune crest is of intermediate size and degree of variability (fig. h) . In each position the sands generally become finer from the base to the top of the dune (fig. 5). Gravel (granules ^ A. to cobbles) * Shore • Dune ° Offshore ■ Nearshore Coarse a medium sand Fine sand, silt, a clay Fig. 3 - Variation in textures of sediments deposited in the modern shore, dune, off- shore, and nearshore environments. Shore Environment Shore sediments show the greatest variation in texture of all mater- ials of the sand body. They range from medium sands of the upper shore area to coarse pebbles where waves break and begin to run up on shore (fig. 6). Sed- - 7 - iments become finer lakeward of the break point as well as shoreward, in agree- ment with the theory and observations of Miller and Zeigler (1958, I96U). A bimodal distribution is generally found at the limit of wave run-up. Variations of this pattern occur, of course, because wave character- istics vary. When waves of higher energy follow lower energy waves, the sedi- ments respond quickly to the new conditions, as sediment distribution and shore profile reach a new equilibrium. However, when the opposite sequence occurs, the sediments and shore profile respond more slowly, and remnants of the respon- ses to former wave conditions may remain under the newer wave regime. When low-amplitude waves strike the shore after waves of greater am- plitude, they form a relatively fine-grained step farther up on the shore from the coarse-grained step formed by the larger waves (fig. 7). The shore sediments become still finer farther up on the shore from the fine-grained step, but they coarsen lakeward to the relatively unmodified coarse-grained wave step. Dune ]y Upper shore Lower shore Feet 10 20 r 12 3 Grain size () tends to become finer in deeper water (fig. ll) . Offshore Environment Offshore sediments, found in water deeper than 15 feet, are the finest material found in the beach ridge complex, other than the clayey, silty, marsh sediments. Sediments in the 15- and 20-foot water depth intervals are predomi- nantly fine to very fine sands. However, some coarse material can be found at - 10 - I- Feel 2 I Sand Granules Fine ond medium gravel A Plunge point for l-fool waves (6/21/73) B Plunge point for 2- to 3- foot woves (6/19/73) C Upper limit of run-up (6/21/73) ffiVftl Coorse gravel 5 Somple location Fig. 7 - Textures developed on a shore (BP7 on fig. 2) where a step developed earlier by 2- to 4-foot waves had not yet been modified by 1- to 2-foot waves that formed a step farther up on the shore. Coarsest textures occur at the break point of the earlier waves and they become fine farther up the shore and also lakeward. A bimodal texture is found at the limit of wave run-up. these depths, especially in the vicin- ity of the Zion nuclear reactor (sam- ples 101U, 1017, 1019 in fig. 12A) and off the northeast coast (sample 10^7, fig. 12A; sample 10U8, fig. 12B) . The coarse material found off the nuclear reactor is associated with abnormal thickening in that area. The coarse material near the Wisconsin state line occurs off a coast that is constantly being eroded; it may represent a lag deposit. Groin size { c °Se°\ Medium and coarse gravel I- 2- 3- Feet 10 L_ 20 _l Grain size W>) Pig. 8 - Textures developed on the surface of a washover bar (BP5 on fig. 2). The bar was built by high waves after a storm that occurred the week before the samples were taken. Wave conditions during the sampling period had modified the lakeward portion of the bar up to point A. Coarsest textures occur at the break point of the modified portion of the bar. Textures become finer grained farther up on the bar and in the swale to the west. cover sediments once deposited in off- shore environments. Marsh and dune sediments have, in turn, been depos- ited on top of the old shore-nearshore deposits as they prograded east and south. The subsurface of the sand body, therefore, is composed of material deposited in offshore, shore, near shore, dune, and marsh environments. The last will not be considered here. It was possible to determine the environment in which sediments recov- ered from the drilling program were deposited by comparing the grain size of these samples with samples taken of sediments deposited in the various modern environ- ments. Isopach (thickness) maps and isolith (lithology) maps of mean grain sizes were constructed for the whole sand body and for each of the facies of the sand body interpreted as having been deposited in dune, shore-nearshore, and offshore environments . Total Sand Body Isopach and isolith maps (fig. 13) show the geometry of the beach ridge complex and the grain-size trends derived from weighted averages of the subsurface samples.* Grain sizes are given in phi () units, which are logarithmic equivalents i e x i v xu -ggi * The average grain size of each facies was d-i'i/iixlxd by the proportion of the total thickness of the sand body occupied by sediments of that facies. The weighted averages were then added together to give the average grain size of the combined facies at that point. - 12 - 2 J Feet 12 3 4 _l l i i 12 Sample location Fig. 9 - Textures in the internal portion of a washover bar (BP6 in fig. 2). Both analysis of grain sizes and sedimentary structures indicate at least two periods of bar development, with intervening periods when the portion of the bars to- ward the lake were modified. of the millimeter scale. Table 1 gives the conversion from millimeters to phi units. The sand body is elongate north to south and prismatic east to west. It thickens lakeward toward the position of the modern shore, thins abruptly from the shore to the 15-foot water depth line, and then continues to thin more gradually eastward. These trends are interrupted off the shore near the Zion nuclear reactor where abnormal thicknesses of sediment may be attrib- uted to an influx of material from Kel- logg Ravine to the west. Some of this material may also be a reflection of Groin size W>) TABLE 1— CONVERSION FROM MILLIMETERS TO PHI UNITS Size mm (i ■■•■■ex? :■:.-'£ . . . . ^j.. o.-. -.g>- ■■ o ■ : '*# a ;'£>■■ &, a ■■■'■&. -II -10 - 9 8 7 6 5 4 - 3 - 2 Fig. 10 - Columnar section and textures of a thick beach ridge exposed by erosion in the summer of 1972. Outcrop occurs in the northern part of Illinois Beach State Park (SW NW NW Sec. 26, T. 46 N., R. 12 E . ) . Shore sediments are slightly- more than 5 feet thick and are capped by dune sands. the disturbance of the southerly longshore drift system created "by the pier con- structed for the -Zion nuclear reactor. The pier was removed before the offshore sampling program was begun, however. The variation in mean grain size in the beach ridge complex has two causes. First, as not all major environments of sand deposition are present everywhere in the complex, the average grain size in any part of the sand body will be affected by the presence or absence of materials normally deposited in these environments. Second, variable conditions during deposition cause a var- iation in grain size within a single environment of the sand body. The average texture of the sand body increases in size westward to- ward the position of the modern shoreline. This is in part due to an increase in grain size westward in sand deposited in the offshore portion of the sand body, and to the addition of coarse shore-nearshore sediments (fig. 1*0. At the position of the modern shoreline, the shore-nearshore sediments are thick- est, and the average texture of the complex in the vicinity of the modern shore is a medium sand. West of the modern shore, however, dunes are present that effect a reduction in the average grain-size of the sand body in that area. - Ik - Grain size i4>) Grain size (<£) Fig. 11 - Range in textures of samples from the nearshore area taken at water depths of from k to 12 feet along the coast from the Wisconsin-Illinois line to the Common- wealth Edison fossil fuel power plant east of Waukegan. The samples generally are composed of medium to very fine sand, although some contain substantial amounts of coarse sand, granules, and pebbles. Dunes are not present in the south-central portion of the complex. In- stead, the western part of the area is occupied by extensive marshes and bogs (Hester and Fraser, 1973). The only sediments present other than marsh deposits are those that formed in the shore-nearshore and offshore environments. As a re- sult, the sand body in that area has an average texture of medium sand, similar to that of the sediments of the modern shore. Discontinuous sand dunes are found on the "western margin of the sand body, and, wherever they appear, these dunes tend to lower the over-all sediment size to that of a medium-fine sand. Textures in areas A and B in figure 13 are somewhat finer than would be expected from their positions in the sand body, and the texture in area C is considerably coarser than would be expected. Areal variations in the textures of the shore materials account for these differences. Shapes and Sediments of the Facies in the Subsurface Dune Facies Because of the irregular topography of the upper surface of the dunes, it is difficult to prepare a standard isopach map of the dune deposits. However, - 15 - A 90- Woter depth: 15 feet /I0I7 / j 1 llll II 6.1- 70- 60- 50- 1019 jjj III U 40- 30^ 1014 II I I i 20- 10- 1047 1 ) 1 ft i i r i l Grain size l) Grain size () Grain size (♦) o I 2 Grain size (<£) Pig. 12 - Range of textures in samples of offshore sediment , taken at water depths of 15 feet or more, from the Wisconsin-Illinois line to Waukegan. Samples are gener- ally in the fine to very fine sand size range, although some contain appreciable amounts of coarse sand, granules, and pebbles. The coarser samples are associated with the abnormal thickness of the sand body in the vicinity of the Zion nuclear reactor (samples 1017, IO19, 1014 in A) or are from the erosional coast on the northern part of the complex (sample 1047 in A and sample 1048 in B). - 16 - wis. ILL. A. Isopach map WIS. ILL. B. Isolith map Location Mop W.s^ J |)J Lone J«' \Michtgonl £ III In«. .-"" Shoreline • Doto point •* Standing water r ^y Isopoch, interval 5 ft pO — Isolith, interval 0.5 4> Fig. 13 - Isopach and isolith maps of complete sand body. The beach ridge complex thickens eastward to the position of the present-day shoreline, where it begins to thin eastward into the lake basin. The coarsest textures of the complex are found in the area of the modern shore. Both east and west of this area textures are finer. - IT - West east -Average texture of sand body- medium-fine sand medium to medium-fine sand medium-fine sand medium sand fine to very fine sand Lake level Colluvium hvft'J Shore and nearshore (coarser) Marsh vWS\ Shore and nearshore (finer) Dune Evvfl Offshore Fig. Ik - Idealized east-west cross section through the beach ridge complex illus- trates the effect that the presence or absence of various units of the complex have on the average textures in any one part of the sand body. The sand body texture is coarsest near the modern shore and where marshes are present, because fine sands of the dunes are absent. The sand body texture is finest from the subaqueous bar eastward because only fine to very fine sands of the offshore facies are present. the area of dune development can be divided, on the basis of thickness, into three areas (fig. 15) » based on the province map in Hester and Fraser (1973) and the soils map for Lake County prepared by Pashke and Alexander (1970). The first area consists of the modern shore. Dune material is thin or absent and is confined to a zone beyond wave run-up where vegetation has acted to trap wind-blown sand. The second area is the high dune field, gener- ally found just west of the modern shore and in an extensive area in the south- ern portion of the sand body. The dunes may be up to 15 feet higher than the adjacent swales. However, the dune sand does not exceed 10 feet thick because the dunes have formed around a core of shore material (fig. h) . The third dune area consists of the low dunes plain in the northern portion of the complex, where dune sands range to only 5 feet thick. Shore and Nearshore Facies Because shore and nearshore facies are difficult to differentiate in the subsurface, the sediment distributions of these two environments were ana- lyzed together. The subsurface shore and nearshore sediments thicken from nothing near the till bluff to a maximum of 15 feet in the vicinity of the modern shore and then thin rapidly into the lake (fig. 16). A cross section through the sand body illustrates the variation in the thickness of the shore and nearshore sed- iments and shows the prismatic shape of these deposits (fig. IT). Since the sand body is prograding eastward, it was expected that the sediments would become finer eastward. The sediments, however, coarsen east- ward from the till bluff, reaching a maximum near the modern shore, and only then - 18 - show the expected fining trend into the lake (fig. 16). This initial coarsening lakeward of the shore-nearshore sedi- ments can possibly be accounted for by the variation in the wave energy that occurs along a curved shore. As King (1972) indicated, varia- tion in wave energy along a shoreline is, at least in part, responsible for variations in grain size parallel to the shore. The component of wave ener- gy parallel to shore is at a minimum when waves approach the shore at angles of 0° or 90° , and it reaches a maximum when waves approach at an angle of U5 . Because the shoreline along the beach ridge complex is curved, wave energy varies considerably along the coast. The winds of greatest velocity measured along the southwestern shore of Lake Michigan are generally from the north and west. Because of the north-north- east south-southeast elongation of Lake Michigan, however, the direction of longest fetch (the continuous area of water over which winds blow) is from the north-northeast , so that waves of greatest energy approach the southwest- ern shore from the northeast quadrant. These waves hit the north-south ori- ented shoreline of the northern two- thirds of the beach ridge complex at an approximately h^° angle, although the pattern may show some variation (Col- linson, 1973, personal communication). Transport energy along the beach ridge complex, therefore, is at a max- imum when the strong waves from the northeast hit the north-south oriented part of the shore. However, at the dis- tal end of the sand body the shoreline curves to the southwest , and waves from the shore at an angle somewhat greater than h^° energy and possibly a reduction in the size -Comp Logon 2 Modern shore (0-2 feet) High dunes (0-10 feel) ]JJ Low dunes (0-5 feef) n Morsh (dunes obsenf) Stonding water Wltj J Lof < \Uichigonl j? III InO Fig. 15 - Thickness of the dune facies. Because of the irregularity of the topo- graphy, a standard isopach map could not be prepared. Instead, the area of dune development was divided into three areas based on the thickness of the dunes in those areas. northeast approach this part of the , causing a reduction in transport of material that can be transported. Hester and Fraser (1973) indicated that as successive beach ridges were built they followed a north-south line for most of their length but curved to the southwest at their distal or southern ends, joining the till bluff at angles of up to 250 from a north-south line. The beach ridges near the till bluff, there- fore , have a north-south trend only in the northern portion of the sand body, which was built first, and they join the till bluff at an increasing angle southward. Where the beach ridges curved to the southwest, wave energy decreased and finer grain sizes were transported around the curve. Therefore, the shore-nearshore - 19 - A. Isopach map B. Isolith map I mile Location Mop fJ .-'' Shoreline Data point ^fe Standing water q-^" Isopach, interval 5 ft ,0°^ Isolith, interval .25* y Fig. 16 - Isopach and isolith maps of shore-nearshore facies. Sediments thicken and coarsen eastward from the till bluff to the position of the present-day- shore. They then thin abruptly and become finer eastward. West - 20 - Plan view of beach ridge hneomenls i angle thai linea- ment makes with a N-S line East L'°V- 1 Pebbles | | Fine sand I •'■•':•■' I Granules \~~~~-\ Silt I :'■••' .'I Coarse sarrd ~\ Clay West L J Medium sand \'—~ 1 Organic material % 560 East Fig. 17 - East-west cross section along Shiloh Boulevard (CS4 in fig. 2) illus- trating the variation in thickness of the shore-nearshore facies. The facies thickens eastward to the position of the modern shore and thins rapidly from there into the lake. The plan view of the lineaments formed by the beach ridges along this cross section are curved to the southwest, as much as 20° from a north-south line near the western margin but only about 10° near the present-day shore, sediments near the bluff, especially at the southern portion of the sand body, are finer grained than those near the lake where the ridges nearly parallel a north-south line. The fine textures found in the shore-nearshore sediments on the west- ern side of the sand body may be due to a decrease in longshore transport energy along the curved portion of the shore. This concept is illustrated in figure IT. The beach ridges gradually become more parallel to a north-south direction going eastward from the till bluff, and the sediments in the shore and nearshore facies become coarser with the addition of pebble layers and coarse sand and granules. The concept also accounts for the anomalously fine textures in areas A and B in figure 13, which are on the southwesterly curving portions of the beach ridge system. The mechanism may not operate on the modern shoreline because it has been artificially modified by man. The isolith map in figure 16 also shows two areas that are coarser than would be expected. The areas coincide with topographic disconformities in the - 21 - beach ridge lineaments formed during former periods of erosion. The disconform- ities are expressed on the surface "by truncations of curved portions of beach ridges (Hester and Fraser, 1973). The subsurface expression of these disconform- ities is a concentration of gravel that was probably left as a lag deposit when beach ridges were eroded. A plan view section of the beach ridges shown above the cross section indicates where such a disconformity occurs (fig. 18). Thick sections of grav- el are found to the east of the erosional boundary, and much finer material is found to the west because of the high angle the lineaments make with a north- south line. Concentrations of gravel left as a lag after an episode of erosion account for the anomalously coarse area C in figure 13, which lies along a pro- nounced topographic disconformity. Offshore Fades Offshore sediments thicken to the east toward the area of the modern shore (fig. 19A) , as would be expected because the till surface on which the offshore sands are deposited slopes gently downward to the east. In the vicin- ity of the modern shore, this trend reverses itself, and offshore sediments be- gin to thin eastward. In the vicinity of the nuclear reactor the sediment is abnormally thick, probably filling in an irregularity in the till surface. Sand size tends to decrease lakeward and silt and clay content to in- crease (fig. 19B). The offshore sands may grade laterally eastward into the silty- clayey facies of the Waukegan Member; which was described by Lineback and Gross (1972). Organic material West East Fig. l8 - East-west cross section through the beach ridge complex along Wadsworth Road (CS3 in fig. 2). The plan view of the lineaments formed by the beach ridges along the cross section show a topographic disconformity near the position of PA5, where ridges oriented at a 24° angle to a north-south line are truncated by ridges oriented in a nearly north-south direction. Gravel layers in the offshore portion of PA7 may be lag deposits formed when erosion truncated the beach ridges. - 22 - WIS. 3 If' ' 1 .1 WIS. i 1 T 46 N T 45 N ILL. I \ \ \ T 46 N ILL. 4 3 fz \ \ 1 9 ■\\ ii A 9 10 « 1 U 1 Q I u A\ I 16 \ ^i •V • v 'o / 1. / * / ■*» 16 13 \ 5 i 1 - 1 14 /! 114 ^-4 21 1 22 ; /-/ / 21 22 / i 26 ■ 'i( 28 27 1 . . [/ % 33 as • 3 _s5 ^ 2_j 33 IK \ 34 t^il ] 35 1 w T 45 N 4 3 1 o 2 1 / 9 10 -i 9 10 16 1 / 15 i -7 / / 16 ( 13 / / / / /// 21 / / * 6' 21 7 / ** 28 i i r 28 1 . . 1 A. Isopach map B. Isolith map Location Mop W.l^ ( UJ Late /j T»t»w j in. Ind ,-' ""* Shoreline Oato point m4* Standing water 4 ^- / Isopach, interval 5 ft .ffl Isolith, interval 0.5<£ Fig. 19 - Isopach and isolith maps of the offshore facies. Sediments deposited in the offshore portion of the sand body thicken eastward toward the position of the modern shoreline. They thin and become finer eastward from there. - 23 - ar a Cd 1 C r-H c •H ;>> o d Ph c g d o c O d « •rH a 0) 0) CD w T3 TJ a) TS 4> 41 a 43 4> Ph 0) •H Ph o co 4) 4) - — » o -C d CM a s 4> _C • d * 43 b0 T3 Pi •rl co Ph 4> "in ■p cd d C 2 C 4) 43 Ph •H £ co 4) •H 4) 43 r<^ d 2 cd CO 4> 2 O co 10 . G CU , H cd •H 43 40 * cd d rt C ■H 4) o Ph H VI •H cd rH Ph ■P > O 4) O Ph 43 4) 0) 43 cd co si C 2 43 o to o Ph to CO 1) o 2 CO 2 Ph o •rH o o si rH CO 4> rH 43 N cd to * — * •H si 41 CM (0 CO 2 1 ■ c >* 4J bO •rH rH CO ■H cd 0) cd liH Ph > W e> •rH c w -d 1 •H . co 4> aj d o c-\ CO Ph cd CM i-l 43 bO U CO a O bO • o 4) Ph bO bO •~> a cd A cross section (fig. 20) of the offshore facies along Wads- worth Road that continues east- ward into the lake also demon- strates the initial thickening eastward to the area of the mod- ern shore , followed by a thinning of the facies from the present shoreline eastward. It also shows the general trend of fining east- ward and coarsening upward. Figure 20 also shows the re- lation of grain size and depth. The texture of the offshore fa- cies becomes coarser toward the west where the sand was deposited in progressively shallower water. The facies also becomes coarser upward as the offshore sands ag- grade and cause a decrease in water depth. The relation of depth to grain size is explained by the null point theory proposed by Cornaglia (l88T) and tested and at least partly verified by Ippen and Eagleson (1955), Eagleson, Dean, and Peralta (1958), and Miller and Ziegler (1958). The null point theory describes the motion of sand grains in the nearshore environment in response to the transport energy of shoal- ing waves. A discussion of the null point theory and its impli- cation for sediment textures can be found in King (1972). RESOURCES FOR BEACH REPLENISHMENT Studies of beach replenish- ment and behavior of fill materi- al have revealed that the stabil- ity of the added materials in the shore environment depends largely on their similarity in textural characteristics to the in-place shore materials. In the study of )dA3| 03$ SAOqo 08j - 2k - requirements for beach nourishment at Presque Isle Peninsula, Erie, Pennsylvania, Berg (1965) discussed the importance of using the proper grain size. He found that the sand fill used for replenishment had a finer mean size than the orig- inal shore material. Because much of the fill material proved to be more com*- patible with processes characteristic of the zone immediately offshore than it was with those of the shore, it was easily eroded and was redeposited in the offshore environment . Krumbein and James (1965) proposed a formula for estimating the amount of borrow material with specific sorting and grain-size parameters that would remain on a shore composed of native materials of known specific parameters. By varying the parameters in the formula independently, they determined the compat- ibility of the materials on a scale of five possibilities, ranging from complete loss of the borrow material, through various conditions of its partial retention, to its stability in the shore environment, which resulted when parameters were matched. In the Zion beach ridge complex, three textural types are present. Two of these, the dune and offshore sands, are finer and better sorted than the shore material. If they were to be used as fill on the shore area, a consider- able transformation of the shore profile would be necessary before much of this fine material would remain on shore. The shore-nearshore sands and gravels of the complex, however, would be well suited for artificial shore replenishment purposes. Thick deposits of this material exist in the subsurface of the beach ridge complex, built up as the sand body has prograded south and east away from the original shore near the till bluff. CONCLUSIONS Because of present high water levels in Lake Michigan, erosion is a serious problem along the coast of the beach ridge complex near Zion, Illinois. Beach replenishment, either by fill or feeding methods, can be used to control this erosion. If beach replenishment is used, the fill must be a material sim- ilar in composition to the present shore. Of the three major environments in the beach ridge complex where sand and/or gravel are currently being deposited, the shore sediments have the coarsest grain size. The finer material from the dune or offshore environments, consequently, would be unsuitable for replenish- ment material. Fortunately, because the shore is part of a sand body that has prograded east and south, coarse material that was once a shore deposit and was subsequently buried is abundantly available in the subsurface of the beach ridge complex. - 25 - REFERENCES Berg, D. W. , 1965 , Factors affecting beach nourishment requirements at Presque Isle Peninsula, Erie, Pennsylvania: Univ. Michigan, Great Lakes Research Division Pub. 13, p. 214-221. Cornaglia, P., 1887, Sul regime della spiagge e sulla regulazione dei porti, cited in C. A. M. King, 1972, Beaches and coasts: St. Martin's Press, New York, 570 p. Curray, J. R., F. J. Emmel , and P. J. S. Crampton, 19^9 » Holocene history of a strand plain, lagoonal coast, Nayarit, Mexico: Lagunas Costeras, un Simposio. Internat. Simp. Lagunas Costeras Mem., UNAM-UNESCO, 1967, Mexico, p. 63-100. Davis, R. A., Jr., W. T. Fox, M. 0. Hayes, and J. C. Boothroyd, 1972, Comparison of ridge and runnel systems in tidal and non-tidal environments: Jour. Sed. Petrology, v. 42, no. 2, p. 413-^21. Eagleson, P. S., R. G. Dean, and L. A. Peralta, 1958, The mechanics of the motion of dis- crete spherical bottom sediment particles due to shoaling waves: U.S. Army Corps Engrs., Beach Erosion Board, Tech. Memorandum 104, 41 p. Hall, J. V., 1952, Artificially nourished and constructed beaches: U.S. Army Corps Engrs., Beach Erosion Board, Tech. Memorandum 29, 25 P- Hester, N. C, and G. S. Fraser, 1973, Sedimentology of a beach ridge complex and its sig- nificance in land-use planning: Illinois Geol. Survey Environmental Geology Note 63, 24 p. King, C. A. M. , 1972, Beaches and coasts: St. Martin's Press, New York, 570 p. Ippen, A. T. , and P. S. Eagleson, 1955. A study of sediment sorting by waves shoaling on a plane beach: U. S. Army Corps Engrs., Beach Erosion Board, Tech. Memorandum 63, 83 p. Krumbein, W. C, and W. R. James, 1965, A lognormal size distribution model for estimating stability of beach fill material: U.S. Army Coastal Eng. Research Center, Tech. Memorandum l6, 17 P- Lineback, J. A., and D. L. Gross, 1972, Deposit ional patterns, facies, and trace element accumulation in the Waukegan Member of the late Pleistocene Lake Michigan Formation in southern Lake Michigan: Illinois Geol. Survey Environmental Geology Note 58, 25 P. Miller, R. L., and J. M. Zeigler, 1958, A model relating dynamics and sediment pattern in equilibrium in the region of shoaling waves, breaker zone, and foreshore: Jour. Geology, v. 66, no. 4, p. 417-441. Miller, R. L., and J. M. Zeigler, 1964, A study of sediment distribution in the zone of shoaling waves over complicated bottom topography, _in Papers in marine geology: Shepard Commemorative Volume, MacMillan Co., New York, p. 133-153. Paschke, J. E., and J. D. Alexander, 1970, Soil survey of Lake County, Illinois: U.S. Dept. Agriculture Soil Conserv. Service, in coop, with Illinois Agr. Exper. Sta. , Washington, D. C. , 80 p. - 26 - Sonu, C. J., and J. L. Van Beek, 197L Systematic beach changes in the Outer Banks, North Carolina: Jour. Geology, v. 79, p. 416-425. Sonu, C. J., 1972, Bimodal composition and cyclic characteristics of beach sediment in con- tinuously changing profiles: Jour. Sed. Petrology, v. 42, no. k , p. 852-857. U.S. Army Corps of Engineers, 1972, Great Lakes shoreline damage: causes and protective measures: U.S. Army Corps Engrs . , North Central Division, General Information Pam- phlet, 22 p. ENVIRONMENTAL GEOLOGY NOTES SERIES (Exclusive of Lake Michigan Bottom Studies) * 1. Controlled Drilling Program in Northeastern Illinois. 19&5- * 2. Data from Controlled Drilling Program in Du Page County, Illinois. 1965. * 3. Activities in Environmental Geology in Northeastern Illinois. 1965. * 4. Geological and Geophysical Investigations for a Ground-Water Supply at Macomb, Illinois. 1965 • * 5- Problems in Providing Minerals for an Expanding Population. 1965 - * 6. Data from Controlled Drilling Program in Kane, Kendall, and De Kalb Counties, Illinois. 1965 . * 7- Data from Controlled Drilling Program in McHenry County, Illinois. 1965 . * 8. An Application of Geologic Information to Land Use in the Chicago Metropolitan Region. 1966. * 9. Data from Controlled Drilling Program in Lake County and the Northern Part of Cook County, Illinois. 1966. *10. Data from Controlled Drilling Program in Will and Southern Cook Counties, Illinois. 1966. *11. Ground-Water Supplies Along the Interstate Highway System in Illinois. 1966. *12. Effects of a Soap, a Detergent, and a Water Softener on the Plasticity of Earth Materials. 1966. *13. Geologic Factors in Dam and Reservoir Planning. 1966. *14. Geologic Studies as an Aid to Ground-Water Management. 1967- *15. Hydrogeology at Shelbyville, Illinois — A Basis for Water Resources Planning. 1967. *l6. Urban Expansion — An Opportunity and a Challenge to Industrial Mineral Producers. 1967- 17. Selection of Refuse Disposal Sites in Northeastern Illinois. 1967 • *l8. Geological Information for Managing the Environment. 1967- *19. Geology and Engineering Characteristics of Some Surface Materials in McHenry County, Illinois. 1968. *20. Disposal of Wastes: Scientific and Administrative Considerations. 1968. *21. Mineralogy and Petrography of Carbonate Rocks Related to Control of Sulfur Dioxide in Flue Gases — A Preliminary Report. 1968. *22. Geologic Factors in Community Development at Naperville, Illinois. 1968. 23. Effects of Waste Effluents on the Plasticity of Earth Materials. 1968. 24. Notes on the Earthquake of November 9, 1968, in Southern Illinois. 1968. *25 . Preliminary Geological Evaluation of Dam and Reservoir Sites in McHenry County, Illinois. 1969 - *26. Hydrogeologic Data from Four Landfills in Northeastern Illinois. 1969- 27- Evaluating Sanitary Landfill Sites in Illinois. 1969 • *28. Radiocarbon Dating at the Illinois State Geological Survey. 1969 - *29. Coordinated Mapping of Geology and Soils for Land-Use Planning. 1969- *31. Geologic Investigation of the Site for an Environmental Pollution Study. 1970- 33. Geology for Planning in De Kalb County, Illinois. 1970. 34. Sulfur Reduction of Illinois Coals— Washability Tests. 1970. *36. Geology for Planning at Crescent City, Illinois. 1970. *38. Petrographic and Mineralogical Characteristics of Carbonate Rocks Related to Sorption of Sulfur Oxides in Flue Gases. 1970. 40. Power and the Environment — A Potential Crisis in Energy Supply. 1970. 42. A Geologist Views the Environment. 1971. 43. Mercury Content of Illinois Coals. 1971. 45. Summary of Findings on Solid Waste Disposal Sites in Northeastern Illinois. 1971 - 46. Land-Use Problems in Illinois. 1971. 48. Landslides Along the Illinois River Valley South and West of La Salle and Peru, Illinois. 1971 • 49. Environmental Quality Control and Minerals. 1971 • 50. Petrographic Properties of Carbonate Rocks Related to Their Sorption of Sulfur Dioxide. 1971 • 51. Hydrogeologic Considerations in the Siting and Design of Landfills. 1972. 52. Preliminary Geologic Investigations of Rock Tunnel Sites for Flood and Pollution Control in the Greater Chicago Area. 1972. 53. Data from Controlled Drilling Program in Du Page, Kane, and Kendall Counties, Illinois. 1972. 55. Use of Carbonate Rocks for Control of Sulfur Dioxide in Flue Gases. Part 1. Petrographic Characteristics and Physical Properties of Marls, Shells, and Their Calcines. 1972. 56. Trace Elements in Bottom Sediments from Upper Peoria Lake, Middle Illinois River — A Pilot Project. 1972. 57- Geology, Soils, and Hydrogeology of Volo Bog and Vicinity, Lake County, Illinois. 1972. 59. Notes on the Earthquake of September 15, 1972, in Northern Illinois. 1972. 60. Major, Minor, and Trace Elements in Sediments of Late Pleistocene Lake Saline Compared with Those in Lake Michigan Sediments. 1973. 61. Occurrence and Distribution of Potentially Volatile Trace Elements in Coal: An Interim Report. 1973. 62. Energy Supply Problems for the 1970s and Beyond. 1973. 63. Sedimentology of a Beach Ridge Complex and its Significance in Land-Use Planning. 1973 • 64. The U.S. Energy Dilemma: The Gap Between Today's Requirements and Tomorrow's Potential. 1973. 65. Survey of Illinois Crude Oils for Trace Concentrations of Mercury and Selenium. 1973 - 66. Comparison of Oxidation and Reduction Methods in the Determination of Forms of Sulfur in Coal. 1973. Out of print. I