Search

Twenty-four new optically stimulated luminescence (OSL) and radiocarbon ages from sediment cores in nine lakes associated with the Shipshewana and Sturgis moraines in northern Indiana and southern Michigan estimate when recession of the Saginaw Lobe of the Laurentide Ice Sheet was underway in the southern Great Lakes region, USA. Average OSL ages of 23.4 ± 2.2 ka for the Shipshewana Moraine and 19.7 ± 2.2 ka for the Sturgis Moraine are considered minimum limiting deglacial ages for these recessional moraines. The much younger radiocarbon ages are consistent with other regional radiocarbon ages from lakes, and record climate amelioration around ~16.5 cal ka BP. Early recession of the interlobate Saginaw Lobe was well underway by 23.4 ± 2.2 ka, when the adjacent Lake Michigan and Huron-Erie lobes were a few hundred kilometers farther south and near their maximum southerly limits. The results provide the first time constraints when sediment from the Lake Michigan and Huron-Erie lobes began filling the accommodation space left by the Saginaw Lobe. The difference between the oldest radiocarbon and OSL age is 7400 yr for the Shipshewana Moraine and 3400 yr for the Sturgis Moraine.

The last aeolian activity of a significant number of inland sand dunes in the southern Great Lakes region (SGLR) was several thousands of years after deglaciation. At Mongo, Indiana, a field of parabolic sand dunes with a variety of morphologies are within the channel bottom of the Pigeon River meltwater channel, with some dunes having climbed up the channel wall onto the adjacent upland surface. The optically stimulated luminescence (OSL) samples from the channel-bottom dunes have a mean age of 14.2 ± 1.6 ka (n = 2) and the OSL samples from upland dunes have a mean age of 12.3 ± 1.6 ka (n = 4). Dunes and outwash ages and geomorphic setting constrain both the position of the Huron-Erie and Saginaw lobes. The oldest dune age is also a minimum age for cessation of local meltwater flow from the Huron-Erie Lobe of the Laurentide Ice Sheet and formation of the adjacent Sturgis Moraine of the Saginaw Lobe. The final activity of the dunes is coincident with late glacial stadial and interstadial events as recorded in the Greenland ice core records, a similar finding to all other studies of dunes in the SGLR. It is now well recognized that many dunes were last active before, during, and after the Younger Dryas stadial, presumably in response to a climate that was windier and less favorable for vegetation.

The Franklin 7.5-minute quadrangle is situated near the maximum limit of Wisconsin Episode glacial deposits insoutheastern Johnson County. Till of Wisconsin Episode age (Trafalgar Formation) dominates the surficial geology of thequadrangle. Areas of Wisconsin Episode outwash (Atherton Formation) are found in the Sugar Creek, Youngs Creek, andHurricane Creek valleys and within former meltwater pathways not occupied by modern streams. Kame deposits (sand andgravel) are found in the northern half of the quadrangle and are part of a larger kame complex present in central JohnsonCounty. Holocene (post-glacial) alluvium is found in the valleys of Sugar, Youngs, Nineveh, Buckhart, and Ray Creeks andtributaries. Unconsolidated sediment thickness generally increases from southwest to northeast across the quadrangle, fromless than 15 ft along the southwestern margin of the quadrangle to over 200 ft thick in the far northeastern corner of thequadrangle. This transition of bedrock topography represents the buried northern end of the Knobstone Escarpment. Twosignificant bedrock paleovalleys exist in the quadrangle, one in the south-central part of the quadrangle which parallels theburied Knobstone Escarpment and one in the northeast corner of the quadrangle which is part of a large bedrock valleyextending north into Marion County. The Quaternary sediments in the western half of the quadrangle are underlain byMississippian Borden Group siliciclastic rocks. In the eastern half of the quadrangle, the Devonian New Albany Shale andMuscatatuck Group carbonate rocks subcrop under thick Quaternary sediment cover. The Wisconsin Episode maximumlimit is located within one mile south of the southern boundary of the quadrangle. Radiocarbon ages from the adjacentTrafalgar 7.5-minute quadrangle indicate the Laurentide Ice Sheet reached its maximum extent just after 23,700 years ago. Asecond glacial limit, marked by the Crawfordsville Moraine in the adjacent Trafalgar 7.5-minute quadrangle,crosses the southern end of the Franklin 7.5-minute quadrangle, albeit diffuse. The Crawfordsville Moraine represents thelimit of a readvance which occurred 21,700 years ago. This preliminary geologic map is an interim geologic map product thatdocuments progress in mapping the Quaternary geology of Johnson County, Indiana. The lithologic classification of theQuaternary units of Indiana was used in assigning map units.

This map provides updated bedrock topography for the eastern extent of the Lafayette Bedrock Valley System in Indiana.

The Mooresville East 7.5-minute quadrangle is situated near the maximum limit of Wisconsin Episode glacial deposits in northeastern Morgan County. Till and outwash of Wisconsin Episode age and Holocene alluvium are the dominant surficial materials in the quadrangle. Wisconsin Episode eolian sand, loess, and colluvium are also present, with eolian sand and colluvium being adjacent to the West Fork White River valley and loess blanketing Wisconsin Episode till and outwash. Holocene (post-glacial) alluvium is found in the West Fork White River and White Lick Creek valleys and tributaries. Mississippian Borden Group bedrock controls many aspects of the surficial geology of the southeastern sector of the quadrangle. For much of this area, bedrock controls the topography and is less than 20 ft below the ground surface. It is mantled on the summits and shoulders of interfluves mainly by Wisconsin till and minor amounts of sand and gravel (outwash) and eolian sand. The depth to bedrock (Borden Group) is greater along the trend of the modern West Fork White River valley, with depths greater than 100 ft. This bedrock paleovalley is filled with mainly Wisconsin Episode outwash (sand and gravel), and the paleovalley was a major path for meltwater in central Indiana during the Wisconsin Episode, from around 27,000 to 19,000 years ago. The Wisconsin Episode maximum limit lies just outside the quadrangle boundary to the south and east. The Laurentide Ice Sheet reached its maximum limit 24,000 years ago, based on radiocarbon dating of organics within till at the terminal moraine in the adjacent Cope quadrangle. Evidence for a readvance of the ice sheet is found in the Mooresville East quadrangle, which occurred 21,700 years ago; the southern limit of the readvance runs through the central part of the quadrangle, just south of State Highway 144.

The Franklin 7.5-minute quadrangle is situated near the maximum limit of Wisconsin Episode glacial deposits insoutheastern Johnson County. Till of Wisconsin Episode age (Trafalgar Formation) dominates the surficial geology of thequadrangle. Areas of Wisconsin Episode outwash (Atherton Formation) are found in the Sugar Creek, Youngs Creek, andHurricane Creek valleys and within former meltwater pathways not occupied by modern streams. Kame deposits (sand andgravel) are found in the northern half of the quadrangle and are part of a larger kame complex present in central JohnsonCounty. Holocene (post-glacial) alluvium is found in the valleys of Sugar, Youngs, Nineveh, Buckhart, and Ray Creeks andtributaries. Unconsolidated sediment thickness generally increases from southwest to northeast across the quadrangle, fromless than 15 ft along the southwestern margin of the quadrangle to over 200 ft thick in the far northeastern corner of thequadrangle. This transition of bedrock topography represents the buried northern end of the Knobstone Escarpment. Twosignificant bedrock paleovalleys exist in the quadrangle, one in the south-central part of the quadrangle which parallels theburied Knobstone Escarpment and one in the northeast corner of the quadrangle which is part of a large bedrock valleyextending north into Marion County. The Quaternary sediments in the western half of the quadrangle are underlain byMississippian Borden Group siliciclastic rocks. In the eastern half of the quadrangle, the Devonian New Albany Shale andMuscatatuck Group carbonate rocks subcrop under thick Quaternary sediment cover. The Wisconsin Episode maximumlimit is located within one mile south of the southern boundary of the quadrangle. Radiocarbon ages from the adjacentTrafalgar 7.5-minute quadrangle indicate the Laurentide Ice Sheet reached its maximum extent just after 23,700 years ago. Asecond glacial limit, marked by the Crawfordsville Moraine in the adjacent Trafalgar 7.5-minute quadrangle,crosses the southern end of the Franklin 7.5-minute quadrangle, albeit diffuse. The Crawfordsville Moraine represents thelimit of a readvance which occurred 21,700 years ago. This preliminary geologic map is an interim geologic map product thatdocuments progress in mapping the Quaternary geology of Johnson County, Indiana. The lithologic classification of theQuaternary units of Indiana was used in assigning map units.

With concerns over rising global temperatures, ice sheet stability and implications for sea level rise, the responses of former ice sheets to past climate change provide useful insights into linkages between the atmosphere, cryosphere and oceans. One example is the behavior of the Laurentide Ice Sheet (LIS) during Heinrich Stadials, times of cooler sea surface temperature (SST) in the North Atlantic. Using existing cosmogenic surface exposure ages, varve chronologies, radiocarbon ages, and optically stimulated luminescence ages from the southern LIS margin, this report tests the hypothesis that the southern side of the LIS advanced during times of surface cooling of the North Atlantic. This test reconstructs the timing of local glacial maxima and the times immediately pro- and preceding them, from multiple areas and compares them to the timing of Heinrich Stadial 2 (HS2; 26.6–23.6 ka) and to the timing of Heinrich Stadial 1 (HS1; 19.3–15.3 ka). During HS2 southern sector lobes (New England region, Huron-Erie Lobe, Lake Michigan Lobe, Green Bay Lobe and the Chippewa Lobe) advanced towards their maximum position, except for the Des Moines Lobe for which there is no applicable data. During HS1 these same lobes experienced substantial retreat, but the Des Moines Lobe advanced. Thus, the southern Laurentide margin behaved differently during the two Heinrich Stadials. This pattern may be attributed to differing east-west temperature gradients across North America and associated changes in atmospheric circulation.

This study examines the influence of analytical particle size on the surface area and mesopore and micropore volume data obtained from low-pressure N 2 and CO 2 adsorption analyses in response to the crushing of coal and shale. Pennsylvanian high-volatile bituminous coal (R o ~ 0.57%) and Devonian to Lower Mississippian low-maturity (R o ~ 0.57%) and high-maturity (R o ~ 1.30%) shales from the Illinois Basin were progressively crushed from chunks (~ 7 mm) to 4 mesh ( 2 and CO 2 adsorption analyses were performed on all the grain size fractions. Our results demonstrate that the values of both surface area and specific mesopore and micropore change with progressive crushing. For example, BET surface area of coal shows a steady increase from 2 m 2 /g in the 4 mesh fraction to 4.7 m 2 /g in the 200 mesh fraction. For comparable size ranges, BET surface area changes from 0.15 to 7.82 m 2 /g in the low-maturity shale, and from 0.02 to 6.26 m 2 /g in the high-maturity shale. Changes in mesoporosity and microporosity parameters indicate that the coarsest fractions (4 mesh and larger) are not suitable for low-pressure adsorption analysis; the values are very low and not reproducible dominantly because of equilibration problems. Our results demonstrate that the 60 mesh fraction for coal and the 200 mesh fraction for shales seem to be optimal and the most practical sizes for performing low-pressure N 2 and CO 2 adsorption analysis; these analytical particle sizes yield results closest to the “real” values, unbiased by disequilibrium.

The North American Ice Sheet Complex (NAISC; consisting of the Laurentide, Cordilleran and Innuitian ice sheets) was the largest ice mass to repeatedly grow and decay in the Northern Hemisphere during the Quaternary. Understanding its pattern of retreat following the Last Glacial Maximum is critical for studying many facets of the Late Quaternary, including ice sheet behaviour, the evolution of Holocene landscapes, sea level, atmospheric circulation, and the peopling of the Americas. Currently, the most up-to-date and authoritative margin chronology for the entire ice sheet complex is featured in two publications (Geological Survey of Canada Open File 1574 [Dyke et al., 2003]; 'Quaternary Glaciations - Extent and Chronology, Part II' [Dyke, 2004]). These often-cited datasets track ice margin recession in 36 time slices spanning 18 ka to 1 ka (all ages in uncalibrated radiocarbon years) using a combination of geomorphology, stratigraphy and radiocarbon dating. However, by virtue of being over 15 years old, the ice margin chronology requires updating to reflect new work and important revisions. This paper updates the aforementioned 36 ice margin maps to reflect new data from regional studies. We also update the original radiocarbon dataset from the 2003/2004 papers with 1541 new ages to reflect work up to and including 2018. A major revision is made to the 18 ka ice margin, where Banks and Eglinton islands (once considered to be glacial refugia) are now shown to be fully glaciated. Our updated 18 ka ice sheet increased in areal extent from 17.81 to 18.37 million km(2), which is an increase of 3.1% in spatial coverage of the NAISC at that time. Elsewhere, we also summarize, region-by-region, significant changes to the deglaciation sequence. This paper integrates new information provided by regional experts and radiocarbon data into the deglaciation sequence while maintaining consistency with the original ice margin positions of Dyke et al. (2003) and Dyke (2004) where new information is lacking; this is a pragmatic solution to satisfy the needs of a Quaternary research community that requires up-to-date knowledge of the pattern of ice margin recession of what was once the world's largest ice mass. The 36 updated isochrones are available in PDF and shapefile format, together with a spreadsheet of the expanded radiocarbon dataset (n = 5195 ages) and estimates of uncertainty for each interval. (C) 2020 Elsevier Ltd. All rights reserved.

Study of past lake-level change and isostasy in the upper Great Lakes has demonstrated the need to reconstruct relative lake-level history at each outlet during the Nipissing phase of ancestral Lakes Huron, Michigan, and Superior. Although elevation and age data exist for the Port Huron/Sarnia and Sault outlets of Lake Huron and Lake Superior, respectively, no paleohydrograph has been created for southern Lake Michigan near the Chicago outlet. The Wentworth Woods area of the Cook County Forest Preserve, Illinois, contains more than 30 beach ridges that formed during the rise and fall from the peak elevation of the Nipissing phase. These relict shorelines were vibracored to recover basal foreshore sediments that can be used as a proxy for lake-level elevation at the time of individual shoreline formation. In addition, sand samples from soil pits and vibracores were collected for optically stimulated luminescence age determinations. This report addresses the sedimentological data used to determine the elevation of the conjoined upper Great Lakes (Lake Nipissing) when each beach ridge formed. The age data will be presented in future reports.

Newly available high resolution elevation data across North America and Europe have revealed previously unknown glacial landforms. This study focuses on the morphology and stratigraphy of a variation of tunnel channels with unique morphology that we have named parallel tunnel channels (PTCs). They are found in northeastern Indiana, northwestern Ohio, and southeastern Michigan, which were previously glaciated by the Huron-Erie Lobe (HEL) of the Laurentide Ice Sheet (LIS). PTCs are discontinuous, quasi-parallel pairs of depressions separated by a continuous central ridge that can extend upwards of 50 km, cross-cut multiple recessional moraines, and transition into standard tunnel channels. The PTCs range in width from 200 to 900 m, and the depressions range in width from 100 to 200 m and in depth from 3 to 10 m. Using water well logs and multiple electrical resistivity surveys, we determined that the stratigraphy beneath and surrounding the PTCs consists of a lower layer of sand and gravel (confined aquifer) and an upper layer of New Holland till, both of the Lagro Formation. A vibracore and multiple resistivity surveys reveal that depressions are filled with ~4 m of lacustrine sediment and occasionally are floored with gravel channel deposits. The depressions are erosional in origin, rather than a product of ice block melt-out and are cut into the upper surface of the New Holland till. We interpret the PTCs as subglacial, erosional landforms, similar to tunnel channels, which represent distinct pathways transporting subglacial meltwater from the interior to the ice margin. Identification of these landforms has several important implications for understanding the deglaciation of the HEL: 1) the major recessional moraines may not record the final deglaciation of the HEL (i.e., are palimpsest features); 2) a large portion of the HEL must have stagnated to preserve the subglacial landscape including the PTCs; and 3) the combined network of PTCs, tunnel channels, and proglacial spillways may represent a partially complete subglacial drainage network with distinct morphological changes as meltwater was transported from the interior to the margin of the HEL. An initial formational model is proposed for the formation of the PTCs by way of a supra- and/or subglacial lake draining through an ice-walled subglacial tunnel, but additional work is required to understand the distinct pattern of depressions observed.

A paucity of research exists regarding the millennial-scale response of inland alluvial streams to abrupt base-level fall. Studies of modern systems indicate that, over short time scales, the response is a diffusion-like process of upstream-propagating incision. In contrast, evidence from the lower Chippewa River (LCR), located in the upper Midwest of the USA, suggests that autogenic controls operating over time scales of several millennia can overwhelm diffusion, resulting in incision that is prolonged and episodic. During the Last Glacial Maximum, the LCR drained the Chippewa Lobe of the Laurentide Ice Sheet to the glacial upper Mississippi River (UMR). As a meltwater stream, it aggraded and filled its valley with glacial outwash, as did its largest tributaries, which were also meltwater streams. Its nonglacial tributaries aggraded, too, filling their valleys with locally derived sediment. During deglaciation, the UMR incised at least twice, abruptly lowering the LCR's base level — ~ 15 m at 16 ka or earlier and an additional 40 m at ca. 13.4 ka. Each of these base-level falls initiated incision of the LCR, led by upstream migrating knickpoints. The propagation of incision has, however, been a lengthy process. The optically stimulated luminescence (OSL) ages of terrace alluvium indicate that, by 13.5 ka, incision had advanced up the LCR only 15 km, and by 9 ka, only 55 km. The process has also been episodic, resulting in the formation of fill-cut terraces (inferred from GPR surveys and exposures of terrace alluvium) that are younger and more numerous in the upstream direction. Autogenic increases in sediment load and autogenic bed armoring, the result of periodic tributary-stream rejuvenation and preferential winnowing of fines by the incising river, may have periodically caused knickpoint migration and incision to slow and possibly stop, allowing lateral erosion and floodplain formation to dominate. A decline in sediment flux from stabilizing incised tributary stream systems would have led to renewed knickpoint migration and incision when floods of sufficient magnitude to breach the channel armor occurred. Minimal floodplain development along the upper section of the present-day LCR, along with the channel morphology of an unstable wandering gravel-bed river immediately downstream from it, suggest that the river is still responding to the base-level falls that happened many millennia ago. The autogenic controls on the LCR's response to UMR incision are a direct consequence of the thick fills of noncohesive sediment that accumulated in its valley and the valleys of its tributary streams during the Late Wisconsinan, making the LCR a prime example of a former proglacial river that remains a paraglacial fluvial system.

Current models of landscape response to Holocene climate change in midcontinent North America largely reconcile Earth orbital and atmospheric climate forcing with pollen-based forest histories on the east and eolian chronologies in Great Plains grasslands on the west. However, thousands of sand dunes spread across 12,000 km 2 in eastern upper Michigan (EUM), more than 500 km east of the present forest-prairie ecotone, present a challenge to such models. We use 65 optically stimulated luminescence (OSL) ages on quartz sand deposited in silt caps (n = 8) and dunes (n = 57) to document eolian activity in EUM. Dune building was widespread ca. 10–8 ka, indicating a sharp, sustained decline in forest cover during that period. This decline was roughly coincident with hydrologic closure of the upper Great Lakes, but temporally inconsistent with most pollen-based models that imply canopy closure throughout the Holocene. Early Holocene forest openings are rarely recognized in pollen sums from EUM because faint signatures of non-arboreal pollen are largely obscured by abundant and highly mobile pine pollen. Early Holocene spikes in nonarboreal pollen are recorded in cores from small ponds, but suggest only a modest extent of forest openings. OSL dating of dune emplacement provides a direct, spatially explicit archive of greatly diminished forest cover during a very dry climate in eastern midcontinent North America ca. 10–8 ka.

The early Holocene final drainage of glacial Lake Minong is documented by 21 OSL ages on quartz sand from parabolic dunes and littoral terraces and one radiocarbon age from a lake sediment core adjacent to mapped paleoshorelines in interior eastern Upper Michigan. We employ a simple model wherein lake-level decline exposes unvegetated littoral sediment to deflation, resulting in dune building. Dunes formed subsequent to lake-level decline prior to stabilization by vegetation and provide minimum ages for lake-level decline. Optical ages range from 10.3 to 7.7 ka; 15 ages on dunes adjacent to the lowest Lake Minong shoreline suggest final water-level decline ∼ 9.1 ka. The clustering of optical ages from vertically separated dunes on both sides of the Nadoway–Gros Cap Barrier around 8.8 ka and a basal radiocarbon date behind the barrier (8120 ± 40 14C yr BP [9.1 cal ka BP]) support the hypothesis that the barrier was breached and the final lake-level drop to the Houghton Low occurred coincident with (1) high meltwater flux into the Superior basin and (2) an abrupt, negative shift in oxygen isotope values in Lake Huron.

The sensitivity of ice sheets to climate change influences the return of meltwater to the oceans. Here we track the Laurentide Ice Sheet along a w400 km long transect spanning about 6000 yr of retreat during the major climate oscillations of the lateglacial. Thunder Bay, Ontario is near a major topographic drainage divide, thus terrestrial ablation processes are the primary forcers of ice margin recession in the study area. During deglaciation three major moraine sets were produced, and have been assigned minimum ages of 13.9 � 0.2, 12.3 � 0.2–12.1 � 0.1, and 11.2 � 0.2 cal ka BP from south to north. These define a slow retreat (w10–50 m/a) prior to major climate oscillations which was then followed by

Meltwater drainage from glacial Lake Agassiz has been implicated for nearly 15 years as a trigger for thermohaline circulation changes producing the abrupt cold period known as the Younger Dryas. On the basis of initial field reconnaissance to the lake's proposed outlets, regional geomorphic mapping, and preliminary chronological data, an alternative hypothesis may be warranted. Should ongoing data collection continue to support preliminary results, it could be concluded that Lake Agassiz did not flood catastrophically into the Lake Superior basin preceding the Younger Dryas (Figure 1). All preliminary findings imply a retreating ice sheet margin approximately 1000 years younger than previously thought, which would have blocked key meltwater corridors at the start of the Younger Dryas.