Glacial Lobes Research Articles

Factors Affecting Iowa Lake and Reservoir Water Quality

ABSTRACT Iowa lake and reservoir water quality data collected during the summers of 1990 and 1992 were analyzed according to origin (lake vs. reservoir) and location, updating previous synoptic surveys. Morphometric comparisons between Iowa regions indicate unique characteristics for reservoirs, glacial lakes, oxbow lakes, and waterbodies on the Des Moines glacial lobe. All Iowa lakes and reservoirs are eutrophic although there is a significant range of water quality and within-region variability. Parameters such as chlorophyll a, total phosphorus (TP), and total nitrogen (TN) summer mean concentrations were highest on the Des Moines glacial lobe (means of 64 μg L−1, 164 μg L−1, and 4.4 mg L−1, respectively). A comparison of northern Iowa versus southern Minnesota lakes and southern Iowa versus northern Missouri reservoirs indicated that Iowa water quality is more eutrophic in both instances. Northern Iowa lakes had higher TN (3.0 mg L−1), total suspended solids (TSS, 39 mg L−1), and non-volatile suspended solids (NVSS, 18 mg L−1) summer mean concentrations than southern Minnesota lakes (2.1 mg L−1, 14 mg L−1, and 3 mg L−1, respectively). Southern Iowa reservoirs had higher TP (149 μg L−1), TN (1.8 mg L−1), TSS (34 mg L−1), and NVSS (25 mg L−1) summer mean concentrations than northern Missouri reservoirs (47 μg L−1, 0.7 mg L−1, 10 mg L−1, and 7 mg L−1, respectively).

Mechanism of cementation in beachrocks based on petrographic and geochemical evidence

SUMMARY OF COMMUNICATIONS REGIONAL EARTH SCIENCES IGc-USPOrganizer: AntonioC.Rocha-Campos TECTONO-SEDIMENTARY EVOLUTION OF THEITARARE SUBGROUP (LATE PALEOZOIC) IN THESOUTHERN PONTA GROSSA ARCH, BRAZIL ∗ JoseR.Canuto,AntonioC.Rocha-CamposandPauloR.Santos Instituto de Geociencias, USP, Sao Paulo, SP. The tectono-sedimentary evolution of the ItarareSubgroup (Late Paleozoic) in the southern flank of thePonta Grossa arch, States of Santa Catarina and Parana,Brazil, isinterpretedthroughstratigraphicanalysisofout-cropping beds. Its evolution seems to have been influ-enced by faulting causing rising and falling of the arch.Thesectionanalyzedrunssome50kmSE-NW,fromMafra (SC)-Rio Negro (PR) to Lapa (PR) and includesabout 700 m thickness of glacio-clastic beds assigned tothe Campo do Tenente and Mafra formations.Paleocurrent orientation, sense of the movement ofthe gravity driven Parana glacial lobe, and stratigraphicdata indicate a basin paleoslope initially dipping 7’ Nduring deposition of the Campo do Tenente Formation.Isopach data shows that the unit fills a large trough trend-ingNW,restingonabradedandstriatedrocksoftheParanaGroup (Devonian). This interpretation implies a tecton-ically negative behavior of the Ponta Grossa arch duringthis time, also shown by isopach maps of palynobiostrati-graphic intervals G and H

Geochronology of ore deposits: new trends about age and lifetime of the hydrothermal systems

SUMMARY OF COMMUNICATIONS REGIONAL EARTH SCIENCES IGc-USPOrganizer: AntonioC.Rocha-Campos TECTONO-SEDIMENTARY EVOLUTION OF THEITARARE SUBGROUP (LATE PALEOZOIC) IN THESOUTHERN PONTA GROSSA ARCH, BRAZIL ∗ JoseR.Canuto,AntonioC.Rocha-CamposandPauloR.Santos Instituto de Geociencias, USP, Sao Paulo, SP. The tectono-sedimentary evolution of the ItarareSubgroup (Late Paleozoic) in the southern flank of thePonta Grossa arch, States of Santa Catarina and Parana,Brazil, isinterpretedthroughstratigraphicanalysisofout-cropping beds. Its evolution seems to have been influ-enced by faulting causing rising and falling of the arch.Thesectionanalyzedrunssome50kmSE-NW,fromMafra (SC)-Rio Negro (PR) to Lapa (PR) and includesabout 700 m thickness of glacio-clastic beds assigned tothe Campo do Tenente and Mafra formations.Paleocurrent orientation, sense of the movement ofthe gravity driven Parana glacial lobe, and stratigraphicdata indicate a basin paleoslope initially dipping 7’ Nduring deposition of the Campo do Tenente Formation.Isopach data shows that the unit fills a large trough trend-ingNW,restingonabradedandstriatedrocksoftheParanaGroup (Devonian). This interpretation implies a tecton-ically negative behavior of the Ponta Grossa arch duringthis time, also shown by isopach maps of palynobiostrati-graphic intervals G and H

Neoproterozoic acid magmatism in western India

SUMMARY OF COMMUNICATIONS REGIONAL EARTH SCIENCES IGc-USPOrganizer: AntonioC.Rocha-Campos TECTONO-SEDIMENTARY EVOLUTION OF THEITARARE SUBGROUP (LATE PALEOZOIC) IN THESOUTHERN PONTA GROSSA ARCH, BRAZIL ∗ JoseR.Canuto,AntonioC.Rocha-CamposandPauloR.Santos Instituto de Geociencias, USP, Sao Paulo, SP. The tectono-sedimentary evolution of the ItarareSubgroup (Late Paleozoic) in the southern flank of thePonta Grossa arch, States of Santa Catarina and Parana,Brazil, isinterpretedthroughstratigraphicanalysisofout-cropping beds. Its evolution seems to have been influ-enced by faulting causing rising and falling of the arch.Thesectionanalyzedrunssome50kmSE-NW,fromMafra (SC)-Rio Negro (PR) to Lapa (PR) and includesabout 700 m thickness of glacio-clastic beds assigned tothe Campo do Tenente and Mafra formations.Paleocurrent orientation, sense of the movement ofthe gravity driven Parana glacial lobe, and stratigraphicdata indicate a basin paleoslope initially dipping 7’ Nduring deposition of the Campo do Tenente Formation.Isopach data shows that the unit fills a large trough trend-ingNW,restingonabradedandstriatedrocksoftheParanaGroup (Devonian). This interpretation implies a tecton-ically negative behavior of the Ponta Grossa arch duringthis time, also shown by isopach maps of palynobiostrati-graphic intervals G and H

Chronostratigraphic dating of carbonates based on 87Sr/86Sr ratio: case studies from Brazilian sedimentary basins

SUMMARY OF COMMUNICATIONS REGIONAL EARTH SCIENCES IGc-USPOrganizer: AntonioC.Rocha-Campos TECTONO-SEDIMENTARY EVOLUTION OF THEITARARE SUBGROUP (LATE PALEOZOIC) IN THESOUTHERN PONTA GROSSA ARCH, BRAZIL ∗ JoseR.Canuto,AntonioC.Rocha-CamposandPauloR.Santos Instituto de Geociencias, USP, Sao Paulo, SP. The tectono-sedimentary evolution of the ItarareSubgroup (Late Paleozoic) in the southern flank of thePonta Grossa arch, States of Santa Catarina and Parana,Brazil, isinterpretedthroughstratigraphicanalysisofout-cropping beds. Its evolution seems to have been influ-enced by faulting causing rising and falling of the arch.Thesectionanalyzedrunssome50kmSE-NW,fromMafra (SC)-Rio Negro (PR) to Lapa (PR) and includesabout 700 m thickness of glacio-clastic beds assigned tothe Campo do Tenente and Mafra formations.Paleocurrent orientation, sense of the movement ofthe gravity driven Parana glacial lobe, and stratigraphicdata indicate a basin paleoslope initially dipping 7’ Nduring deposition of the Campo do Tenente Formation.Isopach data shows that the unit fills a large trough trend-ingNW,restingonabradedandstriatedrocksoftheParanaGroup (Devonian). This interpretation implies a tecton-ically negative behavior of the Ponta Grossa arch duringthis time, also shown by isopach maps of palynobiostrati-graphic intervals G and H

Quaternary geology and geomorphology of the Dinosaur Provincial Park area and surrounding plains, Alberta, Canada: the identification of former glacial lobes, drainage diversions and meltwater flood tracks

The Quaternary geology and geomorphology of the lower Red Deer River drainage basin, centred on the Dinosaur Provincial Park badlands, provides information on pre-Late Wisconsinan drainage patterns and the dynamics of former lobes of the Laurentide Ice Sheet in western Canada. Patterns of deglaciation, proglacial lake evolution and spillway incision are also reconstructed based upon the distribution of surface materials and glacial/glaciofluvial landforms. The Empress Group fluvial and glaciolacustrine sediments, which could be as young as 27 ka BP, infill the precursor Red Deer River and its tributaries and document the initial advance of glacier ice into southern Alberta. Glaciotectonic disturbance of older sediments and bedrock, the production of deformation tills and the construction of a megafluting complex and cupola hills record the advances of a glacier lobe centred over the study area. Stratified inter- and intra-till beds record pulses of subglacial meltwater between phases of subsole deformation. The thickening of tills towards the margin of the lobe represents a till wedge, an expected product of sediment advection by glaciers moving over deformable beds. The eastern margin of the glacier lobe is demarcated by the interlobate Suffield hummocky moraine belt which contains overprinted thrust ridges, which record diachronous oscillations of neighbouring lobes within the ice sheet. Proglacial and glaciofluvial sediments were deposited in the area in association with proglacial Lake Bassano/Patricia, which drained eastwards when the Suffield moraine was dissected by spillways. Changes in the size of glacial lake Bassano/Patricia are clearly documented by a sequence of spillway incisions which culminated in the erosion of scabland topography and the initiation of a new course for the Red Deer River, a 15 km southward diversion of the main channel. In distinct contrast to the documented incision histories of other small rivers in Alberta, One Tree Creek and Little Sandhill Creek did not start major incisions of the Quaternary sediments over buried valley positions until the late-Holocene when environmental conditions were characterized by higher precipitation.

Glacial erosion of the Wash and Fen basin and the deposition of the chalky till of eastern England

It is widely accepted that the low-lying area of eastern England comprising the Wash and the Fens was excavated by the Anglian ice sheet. Moving first from the northwest and then from the north, the ice moved rapidly across the deformable bed on the Jurassic mudrocks and rode up over the Chalk escarpment, eroding the scarp face and setting back the lowered escarpment by several kilometres. The eroded material was deposited beyond the basin as the Chalky till of the southeast Midlands and East Anglia. In this paper reconstruction of the form of the preglacial landscape of the Jurassic and Cretaceous outcrops allows estimation of the excavated volume of both mudrock (312 km 3) and of chalk (243 km 3), a total of about 555 km 3. This volume, and the lithological mix, matches closely the reconstructed volume (estimate 363 km 3) of the now-dissected chalky till around the margins of the glacial lobe. The amount of erosion achieved by the Anglian ice sheet amounts to 3–4000 Bubnoffs (B) — i.e. mm ka −1, even if we allow 20 ka for a complex glaciation; this far exceeds rates of erosion recorded anywhere with the British Isles today: Even if averaged over the 440,000 yr since that event the rate is 167 B, far greater than the erosion achieved on similar rocks within the adjacent unglaciated Thames basin, estimated at 45 B.

Cordilleran Ice Sheet lobal interactions and glaciotectonic superposition through stadial maxima along a mountain front in southwestern British Columbia, Canada

Glaciotectonic structures in subglacial till and substrate, as well as stone fabric, provenance and surface features in till, indicate that complex interactions of late Wisconsinan glacial lobes occurred along a mountain front in the western Fraser Lowland of southwestern British Columbia. Tills of this study represent subglacial deposition through the maxima of two stades in the Fraser Glaciation, the Coquitlam and the Vashon. Through each stadial maximum, temperate glacial ice was grounded and commonly overrode proglacial outwash while superimposing deformations in subglacial till during three phases: (1) pre‐maximum glacier flow down valleys and into lowland piedmont ice, (2) coalescent piedmont ice during stadial maxima when flow was westward along the mountain front and across valley mouths, and (3) post‐maximum glacier flow down valleys into lowland piedmont ice but prior to general deglaciation. Valley glaciers appear to have shifted flow directions during phases 1 and 3. During stadial maxima (phase 2), Fraser Lowland piedmont ice may have been part of an outlet glacier‐ice stream complex that terminated in salt water over the continental shelf.

The Sisters Creek Formation: Pleistocene sediments representing a nonglacial interval in southwestern British Columbia at about 18 ka

Sisters Creek Formation is formally defined, stratotypes are established for it, and the time–space chart is updated for the Fraser Lowland, southwestern British Columbia. The Sisters Creek is a Pleistocene formation comprising in situ and reworked organic-rich sediments, and nonorganic silt, sand, and gravel. The formation was deposited during the Port Moody interstade (within the Late Wisconsinan Fraser Glaciation; δ18O stage 2) between the Coquitlam stade (early Fraser Glaciation) and the main Vashon stadial maximum that occurred about 14.5 ka. The Sisters Creek Formation represents a glacial recession in southwestern British Columbia that generally coincided with the timing of the last global glacial maximum. The new time–space chart implies that, in Fraser Lowland, the Fraser Glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains, which remained ice-covered during interstades.

Lobal interactions and rheologic superposition in subglacial till near Bradtville, Ontario, Canada

Structural, stratigraphic, and lithologic data from a section 69 m long of Catfish Creek drift (north shore of Lake Erie) tell a complex story of two competing glacial lobes. Stone surface features and orientations indicate that stones rotated in viscously deforming, fine‐medium textured subglacial till prior to final emplacement. Fractures, shears, and attenuated sediment lenses in tills reveal that they experienced some brittle shear superposed on ductile shear during till dewatering and stiffening. The Huron‐Georgian Bay lobe advanced first from the northwest, deforming interstadial sediments and depositing subglacial till. Next, southward confluent flow of the Huron, Georgian Bay, and Erie lobes carved subglacial troughs into sediments and deposited (then deformed) bouldery deformation till by squeeze flow. The northwest flowing Erie lobe then prevailed, depositing deformation till, subglacial aquatic sediments, and mudflows. Finally, a pavement‐bearing, hybrid deformation‐lodgement till covered the section. Till formation was mainly by subglacial viscous flow with minor lodgement superposed as water content decreased and some fines were probably winnowed. This implies that till deformation probably accounted for much of the glacier movement. Therefore, rapid ice flow could have occurred over the section, along the southern margin of the Laurentide Ice Sheet.

Search for clues to Mesozoic graben on Long Island

The position of Long Island between the Hartford Basin of Connecticut and graben structures reported from seismic reflection studies offshore to the south of the island suggests the possibility that other grabens associated with the early Mesozoic rifting might be buried beneath central Long Island. The hypothesis that post-rift tectonic activity would be related to the rift grabens and that such activity would be expressed in the post-rift sedimentary deposits led to a study of the Cretaceous and Pleistocene section to seek clues for buried grabens on Long Island. The Pleistocene glacial deposits in central and eastern Long Island have been mapped and a pollen zonation in the Upper Cretaceous section in the central part established. This work, combined with literature research, suggests the following: 1. (1) In central Long Island, the spacing of wells which reach basement enables a NE- striking zone free of basement samples to be defined where a buried graben could occur. This zone is referred to as the “permissible zone” because within it the data permit the existence of a hidden graben. 2. (2) The abrupt changes in the thickness of some pollen zones in the Upper Cretaceous deposits of central Long Island may be related to Cretaceous faulting. 3. (3) Buried preglacial valleys, the confluence of glacial lobes and major glacial outwash channels seem concentrated in west central and central Long Island. The loci of these drainage features may reflect structural control by a basement depression. 4. (4) The “permissible zone” is aligned with the zone of structures in an offshore zone south of central Long Island and with the Hartford Basin in Connecticut. Geophysical anomalies also fit into this pattern. 5. (5) A definitive answer to the question of a buried graben on Long Island will require a seismic line across the “permissible zone”, or further drilling.

Analysis of barrier island surface sediments by scanning electron microscopy

The analysis of quartz grain surface microtextures from a sedimentary environment where grain transport and depositional pathways were closely interconnected, allowed insight into subtle microfeature alteration during movement between subenvironments. Four Fire Island (New York) and one Montauk Point (beach) sample were analysed, principally through use of a checklist approach, using 36 common surface features. Beach, overwash, floodtidal delta, dune and inlet grains displayed similar surface features, only the latter two samples displaying distinctive microtextural patterns. The pattern of development of inlet grains was related to the application of higher shear stresses on the grains during transport in the shallow channel. The results from dune grains testify to the effectiveness of aeolian transport mechanisms in rapidly altering existing features. Glacially derived microtextures altered by subsequent subaqueous action were prevalent but whether these glacial microfeatures are derived from the headland region, Montauk Point, or from a closer offshore “glacial lobe” source is not determined. Comparison of offshore lobe and adjacent sediments revealed contrasting surface and morphological differences. Statistical treatment of checklist data in binary form (1,0) using stepwise discriminant analysis proved workable, but more rigorous testing is required to prove its relevance and use in deciphering raw textural data.

Postglacial Vegetation and Climate in the Northwestern Great Plains of Montana

AbstractTwo pollen records from the northern Great Plains of Montana portray vegetational and climatic changes during the last 12,200 yr in a region where few other data are available. A 6.4-m core from Guardipee Lake, east of the Rocky Mountains in the area formerly covered by the Two Medicine glacial lobe, contains the Glacier Peak G and Mt. St. Helens Jy volcanic ashes. Pollen percentage data are dominated byPinus, Poaceae,Artemisia, and Chenopodiaceae/Amaranthaceae. High nonarboreal percentages and small amounts ofJuniperus, Alnus, Salix, andPopuluspollen in sediments deposited between ca. 12,200 and ca. 9300 yr B.P. suggest a temperate grassland with shrubs growing locally in mesic settings. After ca. 9300 yr B.P. an increase in Chenopodiaceae/Amaranthaceae pollen and a concomitant decline inArtemisiaindicate the development of more xerophytic grassland and the beginning of the altithermal period. The lake probably was intermittently dry thoughout the Holocene. A high sedimentation rate and the presence of cereal taxa characterize the last ca. 100 yr of Euroamerican settlement. Lost Lake at the northern margin of the Highwood Mountains yielded a 16.94-m core with no volcanic ashes that spans the last 9400 yr. High amounts of Chenopodiaceae/Amaranthaceae,Artemisia, and Poaceae pollen, from ca. 9400 to ca. 6000 yr B.P., suggest the presence of xeric grassland and a climate drier than at present. After ca. 6000 yr B.P. Chenopodiaceae/Amaranthaceae values declined andArtemisia, Poaceae,Pinus, Picea, Salix, Alnus, andBetulaincreased. The inferred spread of shrubs in wet habitats at this time and the expansion of forest in nearby mountain ranges indicate the end of the altithermal period and the onset of cooler/moister conditions.

Regional hydrogeology of agricultural drainage wells in Iowa

In Iowa, agricultural drainage wells (ADW9s) represent the largest deliberate transfer of degraded water into major aquifers. An estimated 700 ADW9s remove tile and surface waters from level farmland and inject it into underlying aquifers. Of 174 field-identified ADW9s, 165 were grouped into 3 clusters in north-central Iowa (17 in Floyd County, 44 in Wright County, and 104 in Humbolt-Pocahontas Counties). Geologically, most of the identified ADW9s penetrate the Des Moines glacial lobe and discharge into carbonate aquifers. These aquifers are in the intermediate ground-water flow regime, with recharge mainly from the overlying landscape and discharge mainly to rivers. A graphic flow net model indicates a progressive increase in recharge down gradient, providing increased dilution for contaminants. Modeling suggests that tile-line drainages have averaged about 10-12 ppm nitrate-N during the past decade, mostly derived from fertilizer applications. ADW effluents measured during Spring 1983 ranged between 10 and 20 ppm nitrate-N. Plumes associated with ADW9s would contain nitrate-N in concentrations approaching 20 ppm near the source, decreasing down gradient to 2-6 ppm with ground-water mixing. Joint and bedding-plane openings in the carbonate aquifer formations were measured in quarries, and the effective porosities were about 1%. If it is assumed that diffuse flow approximates isotropic and homogeneous conditions, ground-water flow velocities range from 500 to 26,000 ft/yr. Residence times for ground water in the carbonate aquifers range from a few months to a few decades, depending on the ground-water velocity and the length of individual flow paths.

The dynamics of the ice sheet on the northeastern part of the central Siberian Plateau in the late Pleistocene

Abstract The widespread occurrence of glacial deposits on the Anabar Plateau and adjacent areas is well established. Glacial forms, both erosional and depositional, have been identified, and have allowed the authors to reconstruct the extent and dynamics of the Late Pleistocene ice sheet in this region. Evidence of four active glacial lobes advancing from the NW is presented. These are marked by systems of concentric, arcuate marginal glacial formations which mainly coincide with the topographic depressions in the Trans‐Anabar region. Specific topographical forms typical of stagnant and dead ice are widespread on the Anabar Plateau. The distribution of glacial relief forms provides evidence of the disintegration of a major ice sheet with its center located well to the north of the field area and most probably on the Kara Sea shelf. During one of the deglaciation phases the Anabar Plateau became an obstacle to glacier movement. The ice on the uplands was becoming stagnant while ice streams flowing into the...

Nature and origin of corrugated ground moraine of the Des Moines lobe, Story County, Iowa

Corrugated ground moraine in Story County, Iowa consists of low relief (1–2 m) ridges which most commonly consist of late Wisconsinan till. The average spacing between ridges is about 105 m, and they generally parallel the configuration of the Bemis Moraine, the terminal moraine of the Des Moines glacial lobe. Till fabric (pebble orientations and anisotropy of magnetic susceptibility), facies variations and landform fabric analyzed at three sites in typical corrugated ground moraine landscape near Ames in Story County, Iowa indicate that at sites 1 and 2 the ridges consist of till probably deposited by lodgement. At site 3, two ridges consist of till and massive to cross-bedded sand. Till at site 3 is also probably lodgement till. The nature of the till and related glaciofluvial sediments at each site suggests that the corrugation ridges formed in basal cracks or crevasses in the Des Moines Lobe. The cracks are postulated to have formed during extending flow of the Des Moines lobe as it advanced toward its terminal position. Retreat of the Des Moines lobe was rapid enough to preclude significant accumulations of supraglacial sediment upon corrugated ground moraine.

Rapid soft bed sliding of the Puget Glacial Lobe

The Puget lobe of the late Pleistocene Cordilleran ice sheet advanced into western Washington over a thick sequence of unlithified sediments. The basal drag due to sliding over this surface was calculated by (1) idealizing the sediment bed as a rigid planar surface scattered with roughness elements corresponding to individual sedimentary particles and (2) taking the minimum reconstructed sliding velocity to be 500 m yr−1. The calculated basal drag, minimized by choices of parameters, is 400 kPa, much higher than the reconstructed gravitational driving stress of 40 kPa, indicating that a rigid bed and low water pressure are not consistent with the glacier's rapid motion. High subglacial water pressure, averaging 90% of the ice overburden (10 MPa) is inferred from overconsolidation of subglacial clays. The occurrence and deformation of water‐deposited sediments within the till and the requirement to drain large quantities of water from the interface suggest that water pressure reached 99% of the ice overburden. Ploughing of till by ice‐entrained clasts, pervasive shearing, and, finally, ice‐bed separation become possible as water pressure increases. At the low inferred effective normal stress the basal drag is reduced from the rigid bed case by water layers which decouple the smallest particles from the glacier sole and ploughing which reduces the resistance offered by the largest particles. The limited shear strain observed in much of the till implies pervasive shearing did not contribute significantly to ice motion; basal motion was confined to the ice‐bed interface or to distinct faults within the substrate.

Stratigraphy and correlation of glacial deposits from Indiana to New York and New Jersey

The Quaternary glacial history of part of the region from Indiana to New York and New Jersey (Fig. 1) was outlined in three summaries prepared for the VII Congress of the International Union for Quaternary Research (Wayne and Zumberge, 1965; Goldthwait et al., 1965; Muller, 1965). Subsequent regional summaries by White (1969, 1982), White et al. (1969), Ray (1974) and Coates (1976) reviewed the entire succession of tills in parts of Kentucky, northeastern Ohio, Pennsylvania, and New York. Other syntheses and discussions by Dreimanis and Goldthwait (1973), Evenson and Dreimanis (1976), Dreimanis (1977), Fullerton (1980), Mayewski etal. (1981) and Mickelson et al. (1983) were concerned only with late Wisconsin tills. The glacial history of the region (Fig. 2 and Chart 1) is much more complex than was assumed in 1965. Much of the new information is in unpublished theses and dissertations and other publications of limited distribution, and it has not been summarized. Correlations in Chart 1 are based primarily on stratigraphic relationships of tills and paleosols, and secondarily on radiometric ages, paleomagnetic polarity data, and relativeage data. This summary serves as an expanded explanation of Chart 1. Glacial events are discussed within a framework of time divisions, from older to younger, and by glacial lobes, as shown in Chart 1. Paleomagnetic polarity data in Chart 1 are from Harrison and Terasmae (1961), Bleuer (1976, and pers. commun.), Johnson (1976, this volume and pers. commun.), Hoyer (1977,1983, and pers. commun.), Bonnett et al. (1978) and Teller and Last (1981). Sources of data related to named tills in Indiana, Ohio, Pennsylvania, New York and New Jersey are listed in Appendix 1. The term 'glacial lobe' here is applied both to a regional, physiographically-controlled pattern of ice dispersal and to the geographic region influenced by such movement. Huron-Erie lobe glaciation includes ice movement from the Georgian Bay region, Ontario, into the Lake Erie basin, as well as ice movement through the Lake Huron basin into the Lake Erie basin (Fig. 3). Illinoian and pre-Illinoian tills throughout the region have not been well studied and they have no radio-

Stratigraphy and correlation of the glacial deposits of the glacial lobe complex in Minnesota and northwestern Wisconsin

Stratigraphy and correlation of the glacial deposits of the glacial lobe complex in Minnesota and northwestern Wisconsin

Stratigraphy and correlation of the glacial deposits of the glacial lobe complex in Minnesota and northwestern Wisconsin

Stratigraphy and correlation of the glacial deposits of the glacial lobe complex in Minnesota and northwestern Wisconsin