ABSTRACT This paper presents a detailed sedimentologic data set of minor moraines (heights ≤2.0 m, widths ≤14 m, lengths ≤108 m) that formed beginning near the end of the Little Ice Age by Schwarzensteinkees, a valley glacier in Austria. Sorted sediment and stratified diamict dominate five exposures, and compact massive diamict exists in one exposure. This sediment is interpreted as proglacial outwash and subglacial till. Most moraine sediment shows deformation structures (e.g., smaller and larger folds), and some units contain evidence of water escape. Other units maintain their original subhorizontality. All moraines contain unequivocal evidence of having formed through deformation by pushing during ice-margin fluctuations. Minor moraines formed more specifically by three identified processes: (1) pushing of outwash sediment; (2) stacking and pushing of outwash sediment; and (3) pushing of outwash sediment and freezing-on of subglacial till. Our data suggest that the sedimentologic composition of the valley fill influences the style of push-moraine formation. In this case, the friable nature of outwash sediments can increase the efficiency of the pushing ice front and the likelihood of sediment collapse down the proximal ice-contact slope after ice retreat. This study contributes to our understanding of sediment transport and deposition in high-mountain environments.

ABSTRACT Pleistocene glacial and interglacial episodes had a profound influence on erosion, sediment transport, and topographic expression in the Midwestern United States. Northern Kentucky hosts a variety of fluvial and glacial features that record these Quaternary advances and retreats of the Laurentide ice sheet. This field trip highlights the major glacial and interglacial episodes of the Pleistocene, including the Pliocene–Early Pleistocene Teays drainage system, the Early–Middle Pleistocene pre–Illinois glacial Episode, the Middle Pleistocene Yarmouth interglacial, the Illinois glacial Episode in the Middle Pleistocene, the Sangamon interglacial, and the Late Pleistocene Wisconsin Episode. The Old Kentucky River was tributary to the Teays, depositing sands at ca. 1.5 Ma, confirmed by multiple 10 Be- 26 Al cosmogenic radionuclide burial ages. Glacial till uncoformably overlies Old Kentucky River sands and demonstrates that pre-Illinois ice extended into Kentucky. The modern-day course of the Ohio River was incised after the pre−Illinois Episode, and then aggraded with transportation of Illinois Episode glacial outwash. Deposition of outwash at the mouths of tributaries caused impoundment and slackwater deposition in tributary valleys; the Claryville Clay has long been assumed to represent a pre-Illinois lacustrine deposit, but new optically stimulated luminescence feldspar geochronology yields a Middle Pleistocene age of ca. 320 ka. We have not observed Illinoian till in Kentucky. The final advance of the Laurentide ice sheet did not reach Kentucky, however, high sediment volumes were transported along the Ohio River and impounded tributaries, similar to the Illinois Episode.

ABSTRACT This field guide provides an updated synthesis of the stratigraphy and chronology of glacial deposits in central Indiana near the southern limit of glaciation in the midcontinent. Central Indiana contains evidence of multiple glaciations—deposits from the last two glaciations (Oxygen Isotope Stages [OIS] 2 [Wisconsin Episode] and 6 [Illinois Episode]) have been the focus of recent stratigraphic and chronologic investigation. New radiocarbon and optically stimulated luminescence (OSL) dating from outcrop and core has refined the timing of OIS 2 and OIS 6 ice sheet advances, outwash/slackwater aggradation, glacial lake formation, and eolian activity. Radiocarbon ages within or below late Wisconsin till from three sites within 5 km (3 mi) of the late Wisconsin maximum limit indicate an age of 24.0 k cal yr B.P. for maximum OIS 2 ice sheet extent in central Indiana, consistent with chronology from Illinois and Ohio. A subsequent >50 km (31 mi) readvance (21.6 k cal yr B.P.) across central Indiana came within 10 km (6 mi) of the maximum limit and in the western part of the field-trip area, terminated in glacial Lake Eminence. The start of outwash aggradation and associated slackwater sedimentation in the West Fork White River valley and tributaries began ca. 27 k cal yr B.P. and continued until ca. 20.5 k cal yr B.P., representing the timing of ice sheet advance into and out of the paleo–White River drainage basin. Ice sheet advance and retreat rates average ~40 m/yr before and after the global Last Glacial Maximum (ca. 26−21 k cal yr B.P.) when ice was within ~50 km of the late Wisconsin maximum. OSL dating of pre-Wisconsin outwash and glacio-lacustrine sediment return ages between ca. 218 and 127 ka, confirming deposition during OIS 6. These ages document spatially complex sedimentation in bedrock valleys beyond the Wisconsin limit.

ABSTRACT The Great Miami Buried Valley Aquifer system (GMBVAS) is a U.S. EPA–designated sole-source aquifer for most of the ~2.3 million residents of the Great Miami River basin. The aquifer system is similar to many of the glacial outwash–alluvial aquifers found throughout the southern Midwestern United States: a valley deeply incised into bedrock by meltwater from repeated glaciations, subsequently aggraded with glacial outwash, lake clays, tills, and post-glacial alluvium. These aquifers are often immediately adjacent to or below modern streams with which they are hydrologically connected. Because of the exchange of water between the aquifer and surface streams, they must be considered two parts of a single hydrogeologic system; anything impacting one part will impact the other. Because virtually all water is recycled, public water suppliers, agricultural users, and industrial users withdraw water from the GMBVAS, then discharge the used water to the next downstream consumer. For example, agricultural runoff and municipal wastewater enter the Great Miami River. River water recharges the aquifer near well fields through induced infiltration. Municipalities, agriculture, and industry pump groundwater from the aquifer and discharge some of the water back into the river as a return flow. Sound water management requires balancing the needs of these diverse users. Agriculture, particularly in the upper Great Miami basin, is a major source of revenue and jobs but requires heavy application of nutrients and herbicides. Sand and gravel quarrying in the Great Miami basin is critical for construction and infrastructure but also removes vast amounts of aquifer material. Not only is healthy reliable groundwater important for the public water supply, it is also essential to bottling facilities, distilleries, pharmaceutical companies, and other water-dependent industries that have been attracted to the area. This field trip explores the GMBVAS, its uses, its interaction with Great Miami River, and the contrasting needs of the people and businesses that depend on it.

ABSTRACT Thick successions of glacial sediments are important components of shallow aquifer systems, wetland ecologies, and aggregate resources in northeast Illinois. Multiscale mapping studies have often utilized single surface geophysical methods to locally characterize and map geologic units. In this study, two-dimensional (2-D) electrical resistivity methods were combined with high-resolution shear-wave seismic-reflection methods to better characterize glacial sediments and interpret geologic settings. Study sites were associated with sediments of a Wisconsinan phase of glaciation in northeast Illinois and included a regional bedrock valley, a buried tunnel valley, a pitted outwash fan, and an ice-marginal alluvial fan. Electrical resistivity methods were valuable tools with which to characterize textural relationships within geologic units, and they complement the seismic data with regard to stratigraphic boundaries. The seismic data indicated internal architectural features that were not resolvable with electrical resistivity methods. Thus, the combination of electrical methods and seismic methods improved both the detailed geologic characterization of natural resources as well as understanding of local glacial sedimentology.

Abstract: Late Ordovician ( c. 445 Ma) glacial sandstones form important gas reservoirs in the Illizi Basin, SW Algeria. These reservoirs have a high degree of depositional and diagenetic complexity, such that understanding and predicting reservoir quality (RQ) presents a major challenge to their economic development. Porosity is typically 1–10%, but reaches up to 15% and permeability is typically <10 −15 m 2 (<1 mD), but locally reaches >10 −13 m 2 (>100 mD). The key questions addressed herein concern the development and distribution of this RQ variability, specifically why has good RQ been locally preserved? Primary depositional fabric exerts a strong control on RQ. Muddy sandstones are either highly compacted or pervasively cemented by quartz and microporous illite, and have very poor RQ. Only fine- to medium-grained, moderately well sorted, clean sandstones can contain good RQ, but texturally and mineralogically similar sandstones span a wide range of porosity and permeability. This range is primarily driven by the degree of quartz cementation, with incomplete cementation resulting in the best RQ. Quartz overgrowths in incompletely cemented clean sandstones are patchy and non-luminescent in scanning electron microscopy with cathodoluminescence (SEM-CL), possibly indicating slow growth rates. There is tentative evidence to link incomplete quartz cementation with oil charging of the reservoir. An alternative or additional explanation of RQ preservation may be related to limited silica supply in the centres of the thickest, stacked, clean sandstones, where the better RQ tends to reside. The results of this study imply that sustained high-energy depositional processes, coupled with an early oil charge, are prerequisites for retaining the best RQ. This has important implications for the exploration and development of Late Ordovician glacial sandstones in the Illizi Basin, and potentially similar plays elsewhere.

Poljes are distinctive features of Mediterranean karst landscapes, but their Pleistocene sedimentary fills have not been widely investigated. Most previous research has focused on their formation and hydrology. Many Mediterranean poljes are situated downstream of high mountains that were glaciated during the cold stages of the Pleistocene, so that meltwater streams delivered glacially derived sediment into these basins. This study examines the Pleistocene alluvial records in karst poljes surrounding Mount Orjen in western Montenegro and explores their wider significance. There is a record of at least four glaciations preserved on Mount Orjen—two from the Middle Pleistocene (marine isotope stages [MIS] 12 and 6) and two from the last cold stage (MIS 5d-2), including the Younger Dryas. Detailed sedimentological analysis and uranium-series dating indicate that the Orjen poljes were filled with thick deposits of coarse- and fine-grained alluvium prior to 350 ka, during the major glacial phase of MIS 12. During the cold stages that followed MIS 12, ice was less extensive and limited to the Orjen plateau, and there is little evidence of outwash deposition during these later glaciations. Surface runoff and sediment supply were greatly reduced after MIS 12 and largely channeled into the subterranean karst network. The poljes around Orjen contain some of the best-preserved records of Middle Pleistocene glacial outwash in the Mediterranean, representing an important legacy of an extensive Middle Pleistocene glaciation for which wider impacts have not been fully appreciated.

Abstract This field guide examines Quaternary volcanism in the Canadian Cascade arc informally known as the Garibaldi Volcanic Belt. During the first day, the trip proceeds along the Sea-to-Sky Highway corridor from Vancouver to Pemberton and focuses on Quaternary glaciovolcanic deposits and lavas. Interactions between volcanoes and ice in the Garibaldi Volcanic Belt have been common during the past two million years, which has resulted in a diverse array of landforms, including subglacial domes, tuyas, impounded lava masses, and sinuous lavas that exploited within-ice drainage systems. On Days 2 and 3, the trip heads northwest of Pemberton, British Columbia, along logging roads to see deposits from the 2360 yr B.P. eruption of the Mount Meager volcanic complex. The eruption began Plinian-style, generating pyroclastic fall and density current deposits (Day 2) and ended with the production of welded and nonwelded block and ash flows by explosive (Vulcanian) collapse of a lava (Day 3). The guide will examine the deposits of the temporary lake impounded by a block and ash flow deposit dam, and the evidence of the catastrophic failure of the dam and the generation of a huge outburst flood and lahar. Many of the traits of the deposits seen on this three-day trip are a reflection of both the style of eruption and the nature of the surrounding landscape. In this regard, the trip provides a spectacular window into the nature and hazards of effusive and explosive volcanism occurring in mountainous terrains and the role of water and ice.

Abstract This field guide focuses on the glacial geology and paleoecology beginning in the Paradise Valley and progressing southward into northern Yellowstone National Park. During the last (Pinedale) glaciation, the northern Yellowstone outlet glacier flowed out of Yellowstone Park and down the Yellowstone River Valley into the Paradise Valley. The field trip will traverse the following Pinedale glacial sequence: (1) deposition of the Eightmile terminal moraines and outwash 16.5 ± 1.4 10 Be ka in the Paradise Valley; (2) glacial recession of ~8 km and deposition of the Chico moraines and outwash 16.1 ± 1.7 10 Be ka; (3) glacial recession of 45 km to near the northern Yellowstone boundary and moraine deposition during the Deckard Flats readjustment 14.2 ± 1.2 10 Be ka; and (4) glacial recession of ~37 km and deposition of the Junction Butte moraines 15.2 ± 1.3 10 Be ka (this age is a little too old based on the stratigraphic sequence). Yellowstone's northern range of sagebrush-grasslands and bison, elk, wolf, and bear inhabitants is founded on glacial moraines, sub-glacial till, and outwash deposited during the last glaciation. Floods released from glacially dammed lakes and a landslide-dammed lake punctuate this record. The glacial geologic reconstruction was evaluated by calculation of basal shear stress, and yielded the following values for flow pattern in plan view: strongly converging—1.21 ± 0.12 bars ( n = 15); nearly uniform—1.04 ± 0.16 bars ( n = 11); and strongly diverging—0.84 ± 0.14 bars ( n = 16). Reconstructed mass balance yielded accumulation and ablation each of ~3 km 3 /yr, with glacial movement near the equilibrium line altitude dominated by basal sliding. Pollen and charcoal records from three lakes in northern Yellowstone provide information on the postglacial vegetation and fire history. Following glacial retreat, sparsely vegetated landscapes were colonized first by spruce parkland and then by closed subalpine forests. Regional fire activity increased significantly with the development of closed subalpine forests as a result of increased fuel biomass and warmer summers. Warm dry conditions prevailed at low elevations during the early Holocene, as indicated by the presence of steppe and open mixed conifer forest. At the same time, closed subalpine forests with low fire frequency were present at higher elevations, suggesting relatively wet summer conditions. Douglas fir populations expanded throughout northern Yellowstone in the middle Holocene as a result of effectively drier conditions than before, and a decline of mesophytic plant taxa during the late Holocene imply continued drying, even though fire frequency decreased in recent millennia.

Analysis of geologic materials at the microscale—where we use the term “microscale” to refer to features resolved approximately by a hand lens—has proven to be a powerful strategy to maximize the information gleaned from limited samples, such as on Mars. However, discrimination between processes that leave behind similar traces requires enlightened comparisons to well-characterized analogs. We characterized and imaged several terrestrial analogs of materials produced by volcanic, hydrovolcanic, or cryovolcanic Martian processes at the hand lens scale, and then we produced a convenient tool for the community to access those data for comparisons. We report on the preparation of this Mars-focused image atlas (the Mars Analog Handlens-Scale Image Database), using as an example analog studies of particles deposited by the 1996 Skeiđarársandur jökulhlaup (a jökulhlaup is a subglacially generated outwash flood resulting in a sandur, or sheet of outwash sands and gravel). We imaged unconsolidated sediment particles in situ at about hand lens scale and documented their characteristics at six sites along the sandur. Average particle size and number of angular, very angular, and subangular particles decreased with distance from the source; the average sphericity of particles increased slightly; and the range of sphericity values present narrowed with distance. If observed in a region on Mars, this combination of characteristics would be one indicator that subglacially generated outwash flooding was the process responsible for deposition of sediment. The Mars Analog Handlens-Scale Image Database is searchable and can be found on the Geosciences Node of the Planetary Data System at http://an.rsl.wustl.edu/marsanalog/ .