South-central Michigan Research Articles

Captures of Emerald Ash Borer (Agrilus planipennis) Adults in Post-Invasion White Ash Sites with Varying Amounts of Live Phloem

Emerald ash borer (EAB), (Agrilus planipennis Fairmaire), first identified in 2002 in southeast Michigan, has caused catastrophic ash (Fraxinus spp.) mortality in forests within the core of the invasion and has spread to 35 states and five Canadian provinces. Little is known about persistence and densities of EAB populations in post-invasion sites after most ash trees have died. We monitored EAB populations from 2014 to 2016 using double decker (DD) traps set in the midst of white ash (F. americana) trees in 30 post-invasion sites in southeast and south-central Michigan. Two DD traps were deployed at each site. One trap had a dark green upper prism and light purple lower prism, both baited with cis-3-hexenol lures. The other had two dark purple prisms baited with cis-3-hexenol on the upper prism and Manuka oil on the lower prism. In 2014 and 2016, size and condition of ash trees were recorded and area of live white ash phloem was estimated in an 18-m-radius plot centered around each of the DD traps. Area of live white ash phloem per site ranged from approximately 24 to 421 m2 in 2014 and from 24 to 411 m2 in 2016. Canopy condition of live white ash trees generally improved; 65% and 89% of the trees had healthy canopies (<20% dieback) in 2014 and 2016, respectively. Traps in 28, 29 and 30 of the sites captured a total of 580, 585, and 932 EAB adults in 2014–2016, respectively. Area of live ash phloem explained relatively little of the variation in total EAB captures in all three years. Low trap catches, along with relatively stable canopy conditions and continued abundance of live white ash, indicate that EAB populations remain below the carrying capacity of the sites, and ash phloem availability is not a limiting factor for EAB abundance. Further monitoring to track both EAB dynamics and tree condition is needed to determine the long-term outlook for white ash in these sites.

A Phenology Model for Simulating Oobius agrili (Hymenoptera: Encyrtidae) Seasonal Voltinism and Synchrony With Emerald Ash Borer Oviposition.

In North America, the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), continues to spread, and its egg parasitoid, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae), is being released for emerald ash borer biocontrol well beyond their endemic climatic ranges in China. We developed a multiple cohort rate summation model to simulate O. agrili F0, F1, and F2 generations, and emerald ash borer oviposition for examining host-parasitoid synchrony across a north-south gradient from Duluth, MN (latitude 46.8369, longitude -92.1833) to Shreveport, LA (latitude 32.4469, longitude -93.8242). Temporal occurrences of critical day length for O. agrili diapause induction were integrated into the model. We used O. agrili and emerald ash borer trapping data from south central and northwestern Lower Michigan for model validation. Simulations demonstrated that 1) F0 adult emergence consistently occurred 2-5 d before emerald ash borer oviposition began; 2) F1 adult emergence was most synchronized with peak emerald ash borer oviposition compared with other generations; and 3) emerald ash borer oviposition was complete, or near so, when F2 adult emergence was predicted across the north-south gradient. Comparison of O. agrili trap captures with model simulations demonstrated that primarily two adult O. agrili generations (F0 and F1) emerged per year in Michigan and almost all F2 larvae entered diapause despite day lengths longer than critical day length in south central Michigan. Critical day length varied temporally across the north-south gradient during emergence of O. agrili generations. Determining day lengths perceived by O. agrili larvae in the field should improve model realism for examining spatiotemporal variation in O. agrili population dynamics.

Maternal Mindfulness Is Associated With Lower Child Body Mass Index Z Score.

Parental mindfulness may be a novel intervention target for child obesity prevention. To examine associations between maternal mindfulness and child body mass index z-score (BMIz). In a secondary data analysis of preintervention data from a randomized controlled trial, we assessed survey and anthropometric data from English-speaking mother/child dyads enrolled in Head Start in south central Michigan (n=105). Surveys included demographic information, child dietary intake, family meal frequency, and the Philadelphia Mindfulness Questionnaire. Multivariable linear regression examined associations between maternal mindfulness and child BMIz, child intake of fruits and vegetables, and frequency of family meals. Children were M=53.7 (standard deviation [SD] 7.5) months old, and mothers were M=31.6 (SD 8.3) years old. The sample of children was 39% white, 26% black, 14% Hispanic, and 35% of children were overweight or obese. Mean maternal BMI was 32.0 (SD 8.3). Greater mindfulness was associated with child BMIz (β=-.02 (SE 0.01), P=.027) adjusting for child race/ethnicity, household food security, maternal education, maternal age, and maternal BMI. Mindfulness was not associated with child fruit intake, child vegetable intake or frequency of family meals. The results were consistent with alternative outcomes of BMI percentile (P=.016) and BMI at the trend level (P=.0595) at the trend level. Greater maternal mindfulness was associated with lower child BMIz. Future work should consider mechanisms of association. Pediatric providers might consider supporting maternal mindfulness as one element of multicomponent strategies for child obesity prevention.

Fall Age-Ratio Survey Design for Eastern Population Greater Sandhill Cranes

AbstractFor migratory birds, wildlife managers can use the recruitment rate of young into an adult population to model population dynamics, manage harvest, or evaluate habitat. Few recruitment estimates exist for Eastern Population greater sandhill cranes Antigone canadensis tabida, and estimates are outdated and local in scale. Wildlife managers can use age ratios as an index to recruitment, and surveying at fall staging areas is efficient and cost effective. We created a systematic survey design for surveying eastern population crane age ratios in the Kankakee River valley (2013–2015) in northwestern Indiana and the south-central counties of Michigan (2014–2015). Using logistic regression, we investigated factors that may cause spatial and temporal variation in age ratios, including flock size, timing within season, state, year, random vs. incidental survey routes, and observer. We stratified our selection of survey routes using a core area of high crane abundance, but do not recommend stratifying due to the added complexity and low utility. Observers determined the age of 53,371 cranes and found that the proportion of juveniles in Eastern Population crane flocks (π = 0.113, 95% CI: 0.105 – 0.122) was similar to previous estimates for the population. Proportion of juveniles was greater for south-central Michigan than for the Kankakee River valley, decreased with flock size, increased with lateness in the season, and varied among observers. Our design accounted for both ecological sources of variation in age ratios as well as nuisance variation. We recommend that future surveys use our design as part of a monitoring plan for Eastern Population cranes to support harvest management of the population and ensure that future survey results are comparable across years.

On the banks of the Red Cedar: toward socio-ecologically robust riparian management in an iconic Michigan river

Land use is continually evolving in river watersheds and riparian zones, particularly in areas containing dense human populations requiring infrastructure development. Land use planners in south-central Michigan, USA, are challenged to balance infrastructure needs with the ecological integrity of the iconic Red Cedar River, which flows through the Michigan state capital (Lansing) and surrounding suburban and rural areas and supports freshwater diatoms, mussels, fishes, and other organisms. Although land use goals in the Red Cedar River watershed include protecting riverine biodiversity, decision-makers need a systematic method for predicting and mitigating effects of land use change on the river ecosystem. We developed a framework for evaluating habitat associations of diatoms and native unionid mussels in the Red Cedar River using field collections and mixed-effects modeling to facilitate socio-ecologically informed riparian management. Diatoms were significantly more abundant and genus-rich in riffles and pools than runs, whereas mussels were more abundant in riffles than pools, with intermediate run abundance. Diatom relative abundance was most affected by pH (+ effect), depth (+), and water temperature (+), similar to diatom genus richness (pH and depth +). Mussel relative abundance was best explained by depth (–), pH (+), and percent forest cover (+), similar to mussel length (depth +, pH –). Results from this study underscore riparian management strategies for optimizing forest cover, depth, and pH to promote ecologically favorable conditions for diatoms and mussels in the Red Cedar River (e.g. stable, near-neutral pH; diverse tree species with ≥60% forest cover). Advancing understanding of aquatic biota and their habitats, this research provides a foundation for socio-ecologically balanced land use planning in the Red Cedar River and other riverine ecosystems.

Internalizing Problems in At-risk Preschoolers: Associations with Child and Mother Risk Factors

Internalizing behavior problems such as anxiety and depression impair children’s aptitude to establish contacts with peers and hinder their ability to fully participate in learning activities. Furthermore, early onset of internalizing problems may significantly decrease quality of adult life. The present study examined factors that contribute to internalizing behavior problems among young children. Factors intrinsic to the child and to the child’s family were assessed and analyzed using multilevel modeling techniques to explain variation in internalizing problem behaviors across participating Head Start preschools. The final sample included 183 children ages 3–5.5 years old who were recruited from 15 preschools in rural and urban communities in south central Michigan. Majority (54 %) of children were Caucasian and others were identified as African-American (23 %), biracial (20 %), Hispanic and Native American (3 %). Children’s parents, teachers and case managers reported on behavioral problems, child and family characteristics. Child male gender, externalizing behavior problems, lower maternal education, and lower levels of social support to the mother were significantly associated with higher Achenbach TRF Internalizing behavior scores in young children.

Low-income women's conceptualizations of emotional- and stress-eating

Emotional- and stress-eating have been proposed as risk factors for obesity. However, the way that individuals conceptualize these behaviors is not well understood and no studies have employed a qualitative approach. We sought to understand how women conceptualize emotional- and stress-eating. Sixty-one low-income women from South-central Michigan with young children (ages 2–5 years) participated in either a focus group or individual semi-structured interview during which they were asked about their conceptualizations of eating behaviors among adults and children. Responses were transcribed and the constant comparative method was used to identify themes. Identified themes included that emotional- and stress-eating are viewed as uncommon, severe, pitiable behaviors that reflect a lack of self-control and are highly stigmatized; that when these behaviors occurred among children, the behaviors resulted from neglect or even abuse; and that bored-eating is viewed as distinct from emotional- or stress-eating and is a common and humorous behavior with which participants readily self-identified. Future research and interventions should seek to develop more detailed conceptualizations of these behaviors to improve measurement, destigmatize emotional- and stress-eating and potentially capitalize on the strong identification with bored-eating by targeting this behavior for interventions.

Optimization of Multifunnel Traps for Emerald Ash Borer (Coleoptera: Buprestidae): Influence of Size, Trap Coating, and Color

Field assays were conducted in southeastern and south-central Michigan in 2011 and 2012 to optimize green and purple multifunnel (Lindgren funnel) traps for use as a survey tool for the emerald ash borer, Agrilus planipennis Fairmaire. Larger sized (12- and 16-unit) multifunnel traps caught more beetles than their smaller-sized (4- and 8-unit) counterparts. Green traps coated with untinted (white) fluon caught almost four times as many adult A. planipennis as Rain-X and tinted (green) fluon-coated traps and almost 33 times more beetles than untreated control traps. Purple multifunnel traps generally caught much lower numbers of A. planipennis adults than green traps, and trap catch on them was not affected by differences in the type of coating applied. However, trap coating was necessary as untreated control purple traps caught significantly less beetles than traps treated with Rain-X and untinted or tinted (purple) fluon. Proportions of male beetles captured were generally much higher on green traps than on purple traps, but sex ratios were not affected by trap coating. In 2012, a new shade of purple plastic, based on a better color match to an attractive purple paint than the previously used purple, was used for trapping assays. When multifunnel traps were treated with fluon, green traps caught more A. planipennis adults than both shades of purple and a prism trap that was manufactured based on the same color match. Trap catch was not affected by diluting the fluon concentration applied to traps to 50% (1:1 mixture in water). At 10%, trap catch was significantly lowered.

Effect of green roof media depth on Crassulacean plant succession over seven years

This study follows the succession of 25 succulents (various species of Graptopetalum, Phedimus, Rhodiola, and Sedum) grown at three media depths (2.5, 5.0, and 7.5 cm) over the course of seven years in south central Michigan. Absolute cover was determined using a point-frame transect every two weeks during the first three growing seasons and monthly during years four through seven to measure community composition and change. At the 7.5 cm depth, 22 species were present at the end of the first growing season, but these numbers were reduced to 13, 8, and 7 after two, three, and five years, respectively. Similar results occurred at the shallower depths except that the number of species was reduced at a faster pace. For the most part, the species present did not change after four years, but the relative abundance for each species continued to change. At 5.0 cm and 7.5 cm, both Phedimus spurius and Sedum middendorffianum continued to expand through year 7 at the expense of the other remaining species. At 2.5 cm, Sedum acre and Sedum album were the dominant species. In addition to media depth, an important factor when evaluating green roof plant performance is the length of time that the study is conducted in order to avoid premature conclusions and misleading recommendations. Plants that initially survive may eventually experience reduced coverage or disappear completely due to competition, variability in climate, and other factors. These factors should all be considered during the design and planning phase of a green roof.

Implementing the SCAT Process for a Major Inland Oil Spill: Lessons Learned from the Kalamazoo River Pipeline Release Incident

Abstract On July 26, 2010 an estimated 19,500 bbls of heavy crude oil were released following the rupture of a 30-inch subsurface pipeline in south-central Michigan, USA. After flowing through wetlands and a small creek, oil eventually reached the Kalamazoo River and travelled downstream for a distance of approximately 40 miles. Flooding at the time of the incident carried oil over the riverbanks and into adjacent floodplains containing forested wetlands and other sensitive habitats. Shoreline impacts included fouling of riverbanks and islands, overhanging vegetation and woody debris, as well as stranding of pooled oil within interior portions of floodplains as water levels receded. This poster highlights the shoreline assessment (SCAT) process and programs that were implemented in response to this incident. Particular attention will be paid to unique aspects of this incident atypical of many spills requiring shoreline cleanup. In addition, key lessons learned will be discussed including both positive out...

Estimation and Implications of Space Use for White‐Tailed Deer Management in Southern Michigan

ABSTRACT Studies assessing space use are often descriptive but sometimes lack guidance for managers whose objectives include altering wildlife abundance through habitat management programs. The concept of usable space (i.e., species‐specific permanent cover situations that maximize fitness) collapses commonly used home‐range estimates (e.g., kernel estimators) by excluding cover types contained within individual home ranges that lack direct evidence of use and by reducing cover types containing large areas but small proportions of location estimates. In theory, estimates of usable space provide a potentially more accurate biological representation of space use compared to kernel estimators and provide guidance for managing avoided cover types (i.e., used in a proportion less than available). Our objectives were to compare white‐tailed deer (Odocoileus virginianus) space use under the kernel and usable‐space methods and to discuss the implications of cover conversions under the usable‐space concept. Using radio‐marked adult female deer (n = 20) in south central Michigan, USA, during 2004–2006, we found that fixed‐kernel home‐range estimates (x̄= 77.5 ha ± 9.6 SE for the agricultural growing season, x̄= 140.4 ha ± 23.4 SE for the nongrowing season) included cover types with no evidence of use (e.g., no telemetry locations). Usable‐space estimates (ha) were approximately 75% that of kernel home ranges and were dominated (approx. 87%) by upland deciduous forest, lowland shrub, agriculture, and coniferous cover types. Under the assumption that deer densities are positively correlated with the amount of usable space, we provided several cover‐conversion scenarios (i.e., habitat manipulation) that would theoretically change deer densities on our study area by increasing or decreasing the amount of usable space. Effects of land‐use changes (e.g., increasing urbanization, such as on our study area and throughout much of the midwestern United States) on usable space and inferences on deer population responses may also be assessed using our approach. Regardless of the wildlife species being managed, decisions regarding habitat manipulation are often constrained by several factors (e.g., social, edaphic) and managers should consider ecological processes (e.g., vegetation succession) and implications on broader objectives (e.g., biodiversity conservation).

Multi-scale Cover Selection by White-tailed Deer, <em>Odocoileus virginianus</em>, in an Agro-forested Landscape

Resource selection studies are commonly conducted at a single spatial scale, but this likely does not fully or accurately assess the hierarchical selection process used by animals. We used a multi-spatial scale approach to quantify White-tailed Deer (Odocoileus virginianus) cover selection in south-central Michigan during 2004–2006 by varying definitions of use and availability and ranking the relative importance of cover types under each study design. The number of cover types assigned as selected (proportional use > proportional availability) decreased from coarse (landscape level) to fine (within home range) scales, although at finer scales, selection seemed to be more consistent. Although the relative importance changed substantially across spatial scales, two cover types (conifers, upland deciduous forests) were consistently ranked as the two most important, providing strong evidence of their value to deer in the study area. Testing for resource selection patterns using a multi-spatial scale approach would provide additional insight into the ecology and behavior of a particular species.

Survival and Space Use of Fawn White-tailed Deer in Southern Michigan

ABSTRACT Many cervids exhibit similar behavior near and following parturition. For example, during their first 2 mo of life, fawn white-tailed deer (Odocoileus virginianus) are relatively sedentary, may be at their highest risk for mortality and are not yet functional ruminants. Relatively few studies describe demographics or space use of fawn white-tailed deer ≤2 mo old despite the potential for mortality through this time period having a relatively large influence on deer population dynamics. Our objectives were to estimate survival, assess cause-specific mortality and describe space use (i.e., cover) of fawn white-tailed deer in an agro-forest ecosystem in south central Michigan. We captured (mid-May to mid-Jun.), radiomarked and monitored 34 fawns during 2004–2006 and pooled data for analyses. Two- and 6-mo survival estimates (Mayfield method) were 81% and 67%, respectively, and canids caused most mortalities during both time periods. Kernel home ranges (95%) during the first 2 mo averaged 40.9 ha (ra...

Caddisflies Assist with Homicide Case: Determining a Postmortem Submersion Interval Using Aquatic Insects*

Although few indicators of time since death for corpses found in aquatic ecosystems are comparable in precision to the insect indicators used in terrestrial cases, there are observations that can be useful in suggesting or ruling out an approximate PMSI (postmortem submersion interval). For example, the time intervals required for certain growth phases of aquatic insects, such as caddisflies, that may attach themselves to the submerged remains can be used to estimate a minimum PMSI. Approximately 8 of the 13 orders of insects containing species with aquatic or semi-aquatic stages are likely to be associated with carrion or corpses in aquatic habitats. We present a case study in which portions of a body from an adult male were discovered in a south central Michigan stream. The body was dismembered and portions were recovered from two bags floating and submerged in the stream. Insect specimens collected from mesh and plastic bags consisted of one fly larva belonging to the family Muscidae, and caddisfly larvae belonging to two families: the Limnephilidae. (case-makers) and the Hydropsychidae, (net spinners). We used unique case-building behaviors of the limnephilid caddisflies found on the remains to elucidate a PMSI range consistent with the disappearance of the victim. It is important for forensic investigators to understand that although some precision is lost in estimating a PMSI with aquatic insects, these organisms should not be ignored in gathering evidence from aquatic crime scenes, and in fact, they can provide valuable details in estimating a PMSI.

Sediment TCDD-EQs and EROD and MROD Activities in Ranid Frogs from Agricultural and Nonagricultural Sites in Michigan (USA)

In vitro studies have demonstrated atrazine-mediated induction of 7-ethoxyresorufin O-deethylase (EROD) activity. EROD is an enzyme active in the metabolism of many compounds, including many xenobiotics. These studies have suggested that atrazine may affect reproductive function by altering steroid metabolism. The goal of this study was to determine whether relationships could be detected between measured atrazine concentrations in surface waters and the liver-somatic index (LSI) and EROD and 7-methoxyresorufin O-deethylase (MROD) activities in the livers of ranid frogs. In addition, sediment dioxin toxic equivalents (TCDD-EQs) were determined using the H4IIE-luc cell bioassay. Adult and juvenile green frogs (Rana clamitans), bullfrogs (R. catesbeiana), and Northern leopard frogs (R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south central Michigan in the summer of 2003. Atrazine concentrations at nonagricultural sites ranged from less than the limit of quantification (0.17 microg atrazine/L) to 0.23 microg atrazine/L and did not exceed 1.2 microg atrazine/L at agricultural sites. Sediment TCDD-EQs were measurable only at one agricultural site. Of the measured parameters, only LSI values in adult male frogs differed significantly between agricultural and nonagricultural sites, with greater values observed at agricultural sites. In green frogs, EROD and MROD activities were measurable in both adult and juvenile frogs and were similar among sites. Median EROD activities ranged from 13 to 21 pmol/min/mg protein in adult male green frogs and from 5 to 13 pmol/min/mg protein in adult female green frogs. Juvenile frogs had greater EROD and MROD activities than adult frogs. Bullfrogs and leopard frogs had greater activities than did green frogs. Atrazine concentrations were significantly and negatively correlated with MROD activity in adult male green frogs (Spearman R = -0.800). LSI and EROD and MROD activities of adult female or juvenile green frogs were not significantly correlated with atrazine concentrations. These results suggest that atrazine does not appear to have a consistent association with EROD or MROD activities in wild-caught green frogs.

Plasma steroid hormone concentrations, aromatase activities and GSI in ranid frogs collected from agricultural and non-agricultural sites in Michigan (USA)

The triazine herbicide atrazine has been hypothesized to disrupt sexual development in frogs by up-regulating aromatase activity, resulting in greater estradiol (E2) concentrations and causing feminization in males. The goal of this study was to collect native ranid frogs from atrazine-exposed ponds and determine whether relationships exist between measured atrazine concentrations and the gonadosomatic index (GSI), plasma concentrations of testosterone (T), E2 or 11-ketotestosterone (KT), or with aromatase activity. In the summer of 2002 and 2003, adult and juvenile green frogs ( Rana clamitans), bullfrogs ( R. catesbeiana) and Northern leopard frogs ( R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south-central Michigan. Atrazine concentrations were below the limit of quantification at non-agricultural sites. Atrazine concentrations did not exceed 2 μg/L at most agricultural sites, but a concentration of 250 μg atrazine/L was measured in one sample from one site in 2002. Plasma steroid concentrations varied among locations. Aromatase activity was measurable in less than 11% of testes in adult males, and in less than 4% of testes in juvenile males. Median aromatase activities in ovaries of adult females ranged from 3 to 245 pmol/h/mg protein, and maximum activities were 2.5-fold greater in juveniles than in adults. Atrazine concentrations were not significantly correlated with any of the parameters measured in this study. These results indicate that atrazine does not up-regulate aromatase in green frogs in the wild, and does not appear to affect plasma steroid hormone concentrations.

Saginaw Lobe tunnel channels (Laurentide Ice Sheet) and their significance in south-central Michigan, USA

A network of tunnel channels in southern Michigan records substantial subglacial meltwater activity beneath the Saginaw Lobe of the Laurentide Ice Sheet. The channels are incompletely filled with outwash, contain eskers, and in many places crosscut and continue beyond upland ridges previously mapped as recessional moraines. The presence of the tunnel channels and drumlins on these upland ridges indicate that the ridges are not recessional moraines. Instead, outwash fans and minor ridges record deglaciation in the area. A palimpsest relationship between buried bedrock valleys and tunnel channels records the presence of multiple generations of tunnel channels. Evidence for a subglacial meltwater sheetflow consists of sheets of boulder gravel in upland >15 km wide with a hummocky upper surface. The hummocks transform down flow into erosional remnant drumlins; possibly the result of flow acceleration on a negative slope. Tunnel channels at the distal end of the drumlin swarm suggest collapse of the sheetflow into a channelized flow. The tunnel channels then end at the Sturgis Moraine at the heads of large outwash fans. The observed geomorphic relationships between tunnel channels, moraines, and drumlins in south-central Michigan are applicable to glacial landform studies elsewhere, and indicate the important role of meltwater in landscape evolution.

Sarcocystis inghami n. sp. (Sporozoa: Sarcocystidae) from the skeletal muscles of the Virginia opossum Didelphis virginiana in Michigan.

This report describes the newly identified Sarcocystis inghami n. sp. from the skeletal muscles of opossums (Mammalia: Didelphidae) that were collected from south central Michigan (42 degrees 43'-42 degrees 79'N, 84 degrees 18'-84 degrees 86'W), USA. The new species is distinguished from all species described from North and South American opossums by the distinctive morphology of the villar protrusions on the cyst wall. Sarcocysts of S. inghami are microscopic, up to 700 microm long and 110 microm wide. The sarcocyst wall is up to 7 microm thick, with long, stalked protrusions which average 5.5 x 1.2 microm. These are constricted at the base, expanded laterally, rounded off distally and occasionally bifid. The villar protrusions have numerous microtubules without electron-dense bodies that extend from the tips into the granular layer. Bradyzoites are 10.7 x 4.3 (8-12 x 4-5) microm. This is the second species of Sarcocystis sarcocyst described from the Virginia opossum in North America.

Boulder‐gravel hummocks and wavy basal till contacts: products of subglacial meltwater flow beneath the Saginaw Lobe, south‐central Michigan, USA

Hummocky terrain composed of boulder gravel and a wavy contact between stratified till and sand are described and explained as products of subglacial meltwater activity beneath the Saginaw Lobe of the Laurentide Ice Sheet in south‐central Michigan. Exposures and geophysical investigations of hummocky terrain in a tunnel channel reveal that hummocks (˜100m diameter) are glaciofluvial bedforms with a supraglacial melt‐out till or till flow veneer. The hummocky terrain is interpreted as a subglacial glaciofluvial landscape rather than one of stagnant ice processes commonly assumed for hummocky landscapes. Sandy bedforms at another site are in‐phase with a wavy contact at the base of a stratified till exposed for 50m along the margin of a tunnel channel. The 0.4m thick stratified till is overlain by up to 5m of compact, pebble‐rich, sandy subglacial melt‐out till. The contact between the till and sand has a wave form with a 0.5m amplitude and 3‐5m wavelength. Bedding within the stratified till, sandy bedforms and melt‐out till are mostly in‐phase with each other. Clasts from the overlying stratified till penetrate and deform the underlying sand recording recoupling of the ice to its bed. Ice ripples cut into the base of river ice have a similar morphology and are considered analogs for cavities cut into the base of the glacier and subsequently filled with sand. Subglacial meltwater activity was not coeval at each study site, indicating that subglacial meltwater played important roles in the evolution of the subglacial environment beneath the Saginaw Lobe at different times.

Boulder-gravel hummocks and wavy basal till contacts: products of subglacial meltwater flow beneath the Saginaw Lobe, south-central Michigan, USA

Boulder-gravel hummocks and wavy basal till contacts: products of subglacial meltwater flow beneath the Saginaw Lobe, south-central Michigan, USA