Mississippi River Valley Research Articles

Comparative phylogeography of two cavernicolous springtails (Collembola) codistributed across a geologically complex karst landscape

Genetic isolation and biological diversification in caves is generally attributed to physical barriers to gene flow, but few studies have evaluated the influence ecology has on patterns of divergence and molecular variation in cave organisms. Collembola (springtails)—a class of tiny, insect-like arthropods—constitute an under-utilized and information-rich source of data for inferring evolutionary processes in cave environments. They are among the most abundant and diverse animals in caves with species that are often codistributed and have varying levels of ecological specificity to, or dependence upon, cave habitats—differences that may affect dispersal capacity and genetic connectivity. This is the first study to characterize and compare patterns of molecular diversity and genetic structure among ecologically distinct and codistributed species of cavernicolous springtails. Twenty-five caves were sampled throughout the Salem Plateau in Illinois and Missouri—a once continuous karst region, now bisected by the Mississippi River Valley. Multilocus datasets generated for morphospecies in the genera Pygmarrhopalites and Pogonognathellus were used to delimit species, identify genetic barriers, and evaluate and compare phylogeographical patterns between troglobiotic and eutroglophilic species to assess whether two codistributed cave-dwelling species have congruent phylogeographical patterns across a complex geological landscape, despite having distinct ecologies. Populations of troglobiotic Pygmarrhopalites sp. were strongly structured among karst areas and across the Mississippi River valley, but these patterns were not recovered for eutroglophilic Pogonognathellus sp., which displayed little to no genetic structure, except among caves. Results indicate that cave-dependence is associated with deep phylogeographic divisions across geographical barriers—supporting the hypothesis that ecological specialization to cave habitats is correlated with low dispersal capacity. The recovery of highly divergent and cryptic lineages, genetically isolated at fine geographic scales (microendemism), also highlights how little we understand microarthropod diversity in caves and presents major concerns for cave conservation biology.

Geochemistry and mineralogy of late Quaternary loess in the upper Mississippi River valley, USA: Provenance and correlation with Laurentide Ice Sheet history

The midcontinent of North America contains some of the thickest and most extensive last-glacial loess deposits in the world, known as Peoria Loess. Peoria Loess of the upper Mississippi River valley region is thought to have had temporally varying glaciogenic sources resulting from inputs of sediment to the Mississippi River from different lobes of the Laurentide Ice Sheet. Here, we explore a new method of determining loess provenance using K/Rb and K/Ba values (in K-feldspars and micas) in loess from a number of different regions in North America. Results indicate that K/Rb and K/Ba values can distinguish loess originating from diverse geologic terrains in North America. Further, different loess bodies that are known to have had the same source sediments (using other criteria) have similar K/Rb and K/Ba values. We also studied three thick loess sections in the upper Mississippi River valley region. At each site, the primary composition of the loess changed over the course of the last glacial period, and K/Rb and K/Ba values parallel changes in carbonate mineral content and clay mineralogy. We thus confirm conclusions of earlier investigators that loess composition changed as a result of the shifting dominance of different lobes of the Laurentide Ice Sheet and the changing course of the Mississippi River. We conclude that K/Rb and K/Ba values are effective, robust, and rapid indicators of loess provenance that can be applied to many regions of the world.

Rapid climate change-induced collapse of hunter-gatherer societies in the lower Mississippi River valley between ca. 3300 and 2780 cal yr BP

Hunter-gatherer communities in the American Southeast reached an apogee of social and political complexity in the period between ca. 4200 and 3000 cal yr BP. In the lower Mississippi Valley (LMV) the Poverty Point culture defined this period of socio-political elaboration. However, following a significant period of climate change that led to exceptional flooding and a major reorganization of the course of the Mississippi River, this culture collapsed beginning ca. 3300–3200 cal yr BP and the LMV was abandoned for the subsequent 500 years. In this study, we use data from the Jaketown site in the Yazoo Basin of west-central Mississippi to refine the chronology of the climate event that caused the collapse of the Poverty Point culture. A large flood buried Poverty Point-era occupation deposits at Jaketown around 3310 cal yr BP. Lateral migration of the Mississippi River during flooding led to inundation of the Yazoo Basin and re-occupation of ancient river courses. A coarse sand stratum topped by a more than a meter-thick fining upward sediment package marks a crevasse deposit caused by a rupture of the natural levee at Jaketown. This levee breach was part of a larger pattern of erratic flooding throughout the LMV and is associated with major landscape evolution and the abandonment of Poverty Point sites within the valley. Early Woodland peoples re-colonized the crevasse surface after ca. 2780 cal yr BP. Following this event, the Jaketown site and the eastern Yazoo Basin witnessed a period of landscape stability that lasts to this day. These archaeological data demonstrate how climate change and natural disasters can lead to socio-political dissolution and reorganization even in relatively small-scale hunter-gatherer populations.

The geochemistry of loess: Asian and North American deposits compared

Loess is widely distributed over Asia and North America and constitutes one of the most important surficial deposits that serve as terrestrial records of the Quaternary. The oldest Pleistocene loess in China is likely ∼2.6 Ma, thus spanning much or all of the Pleistocene. In North America, most loess is no older than the penultimate glacial period, with the exception of Alaska, where the record may go back to ∼3.0 Ma. On both continents, loess deposits date primarily to glacial periods, and interglacial or interstadial periods are represented by paleosols. Both glacial and non-glacial sources of silts that comprise the bulk of loess deposits are found on both continents. Although loess has been considered to be representative of the average upper continental crust, there are regionally distinctive compositions of loess in both Asia and North America. Loess deposits in Asia from Yakutia, Tajikistan, and China have compositionally distinct major element compositions, due to varying abundances of silicate minerals, carbonate minerals, and clay minerals. In North America, loess in the Mississippi River valley, the Great Plains, and Alaska are also distinguishable with regard to major element composition that reflects highly diverse source sediments. Trace element geochemistry (Sc-Th-Zr and the rare earth elements) also shows regional diversity of loess bodies, in both Asia and North America. On both continents, most loess bodies show significant contributions from later-cycle, altered sedimentary rocks, as opposed to direct derivation from igneous rocks. Further, some loess bodies have detectable contributions from mafic igneous rocks as well as major contributions from average, upper-crustal, felsic rocks. Intercalated paleosols in loess sections show geochemical compositions that differ significantly from the underlying loess parent materials. Ratios of soluble-to-insoluble elements show depletions in paleosols due to chemical weathering losses of calcite, dolomite, plagioclase, mica, apatite, and smectite. In Asia and North America, the last interglacial paleosol is more weathered than equivalent modern soils, which could be due either to a climate that was warmer and more humid, a longer period of pedogenesis, or both. In Asia, early Pleistocene loess and paleosols are both more weathered than those from the middle and late Pleistocene, forming prior to a mid-Pleistocene aridification of Asia from uplift of the Tibetan Plateau. Understanding the geochemistry of loess and paleosols can tell us much about past atmospheric circulation, past temperature and moisture regimes, and even tectonic processes.

Accuracy Analysis Comparison of Supervised Classification Methods for Anomaly Detection on Levees Using SAR Imagery

This paper analyzes the use of a synthetic aperture radar (SAR) imagery to support levee condition assessment by detecting potential slide areas in an efficient and cost-effective manner. Levees are prone to a failure in the form of internal erosion within the earthen structure and landslides (also called slough or slump slides). If not repaired, slough slides may lead to levee failures. In this paper, we compare the accuracy of the supervised classification methods minimum distance (MD) using Euclidean and Mahalanobis distance, support vector machine (SVM), and maximum likelihood (ML), using SAR technology to detect slough slides on earthen levees. In this work, the effectiveness of the algorithms was demonstrated using quad-polarimetric L-band SAR imagery from the NASA Jet Propulsion Laboratory’s (JPL’s) uninhabited aerial vehicle synthetic aperture radar (UAVSAR). The study area is a section of the lower Mississippi River valley in the Southern USA, where earthen flood control levees are maintained by the US Army Corps of Engineers.

A Colonic Mass, Abdominal Pain and Gastrointestinal Bleeding: A Presentation of Gastrointestinal Involvement in Disseminated Histoplasmosis

A Colonic Mass, Abdominal Pain and Gastrointestinal Bleeding: A Presentation of Gastrointestinal Involvement in Disseminated Histoplasmosis

A Rare Case of Gastrointestinal Histoplasmosis in an Immunocompromised Host

Introduction: Histoplasmosis capsulatum (HC) is a dimorphic fungus common to the Ohio and Mississippi River valleys and is found mainly in soil enriched by avian or bat droppings. It typically presents as an asymptomatic pulmonary infection. Gastrointestinal (GI) involvement is usually unrecognized due to nonspecific symptoms and is thought to be symptomatic in only 3 to 12% of patients. The majority of GI histoplasmosis involves patients with HIV/AIDS. The most common site of GI involvement is the ileocecal region due to the presence of abundant lymphoid tissue. Case Presentation: A 64-year-old man with paroxysmal atrial fibrillation (on warfarin), end stage renal disease on hemodialysis, status post failed transplanted kidney and on chronic immunosuppression presented with a one day history of hematochezia and hematemesis and six weeks of worsening left lower quadrant abdominal pain. CT thorax with intravenous contrast revealed a right lower lobe cavitary mass and a spiculated left upper lobe nodule (Figure 1). Esophagogastroduodenoscopy with enteroscopy revealed old blood in stomach and the endoscope was advanced into the jejunum revealing multiple ulcers (Figure 2). Histopathology from jejunal biopsies was consistent with HC (Figure 3). Histoplasmosis antibodies by complement fixation for yeast and mycelia were positive as was fungal immunodiffusion for Histoplasma M antigen. Histoplasmosis serum antigen was negative. The patient was treated with intravenous amphotericin for presumed disseminated histoplasmosis. He improved clinically with resolution of symptoms and was discharged on oral itraconazole and remains therapeutic five months later.Figure: CT thorax with intravenous contrast showing (A) 21mm right lower lobe cavitary mass (B) and 19mm left upper lobe spiculated nodule.Figure: Ulcerations of proximal (A) and mid-jejunum (B).Figure: Gomori methenamine silver (GMS) stain of jejunal biopsy specimen showing budding yeast form of histoplasmosis capsulatum.Discussion: Histoplasmosis capsulatum is generally seen in immunocompromised hosts. While common at autopsy, gastrointestinal histoplasmosis (GIH) goes unrecognized during life as the symptoms are nonspecific. Patients with GIH most commonly present with abdominal pain and diarrhea, but may also have dysphagia, odynophagia, bowel obstruction or perforation. In this case, the patient presented with clinically significant gastrointestinal bleeding. Upper endoscopy with jejunal biopsies revealed HC. Both the presence of symptomatic GIH and the jejunal location are atypical. This observation in a patient without HIV is exceedingly rare.

The acoustics and sound environments of Early Delta Blues

As part of a larger investigation into the archaeological origins of the blues, I seek to re-create the sound environments that surrounded and informed the initial emanations of this important American music genre. This study is warranted because the music has had such a pronounced influence on global musics, as well as on broader sociological concerns like race, regionalism, nationalism, capitalism, and gender. It is also of value for archaeo-acoustic studies in that it concerns a study of an archaeo-historic site that is not in the deep past. For the ASA meeting-forum I will report on two related acoustic processes: one is the digital reconstruction of the physical structures where the blues was first heard, such as wood-framed shotgun-shaped performance spaces (juke joints, general stores), some of which still exist in the Mississippi Delta (Po Monkeys near Merigold and Mary’s in Indianola), or can be archaeologically recovered (the general store at Dockery Farms); and the second process is a recreation of the sonic environment of the late 19th early 20th century south of the lower Mississippi river valley, including natural and anthropomorphic sounds. These steps precede a future goal, the archaeologically reconstructed instrumental and vocal sounds of incipient and early blues, allowing for a truer picture of this musical phenomenon than currently exists.

Disseminated Histoplasmosis in an Immunocompetent Host

SESSION TITLE: Fellow Case Report Poster - Chest Infections I SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 25, 2016 at 01:30 PM - 02:30 PM INTRODUCTION: Histoplasmosis is the most common endemic mycosis in the United States with higher prevalence in states along the Ohio and Mississippi River valleys. Approximately 500,000 new infections occur each year though clinically significant disease rarely manifests.1 Even more unusual is symptomatic disease in a host with intact cell-mediated immunity. We present a case of disseminated histoplasmosis in an immunocompetent host. CASE PRESENTATION: A 44-year-old man presented with several weeks of malaise, weakness, lymphadenopathy, and fevers. He endorsed a 60-lb weight loss over the past year that he attributed to poor oral intake due to a large tongue ulceration that he thought he incurred after biting his tongue during a seizure. Past medical history included seizure disorder and remote history of skin squamous cell carcinoma on the lower abdomen status post wide excision. Interestingly, he had an inguinal lymph node excision at that time that was remarkable for non-caseating granulomatous inflammation. The patient was found to be septic thus started on broad-spectrum antibiotics. CT neck, chest, and abdomen were performed demonstrating development of extensive small cysts with associated consolidation. Diffuse lymphadenopathy was also noted suggesting the presence of a reactive process. Immunosuppression workup was negative. Within 12 hours of presentation, he experienced acute respiratory failure requiring endotracheal intubation. Fiberoptic bronchoscopy with brocheoalveolar lavage (BAL) was performed. Over the next 24-hrs the patient continued to deteriorate requiring escalating vasopressor support. He eventually went into pulseless electrical activity arrest and 36-hrs after presenting to the hospital, died. Pathology from BAL returned demonstrating histoplasmosis. DISCUSSION: Histoplasmosis is a reportedly rare symptomatic disease in the immunocompetent host; disseminated disease is even more elusive. Often in this patient population it is not included in the differential as more common entities like bacterial pneumonia are presumed. However, without early bronchoscopy, this patient’s actual diagnosis would have been missed. CONCLUSIONS: Disseminated histoplasmosis is a rare disease in the immunocompetent host. A high index of suspicion in endemic areas along with early bronchoscopy when pulmonary involvement is present is necessary for diagnosis to avoid potentially fatal outcomes through treatment delays. Reference #1: Kauffman CA. Histoplasmosis: a clinical and laboratory update. Clin Microbiol Rev. 2007;20(1):115 DISCLOSURE: The following authors have nothing to disclose: April McDonald, Kiran Joglekar, Amik Sodhi, Dipen Kadaria No Product/Research Disclosure Information

Impacts of Local Soil Moisture Anomalies on the Atmospheric Circulation and on Remote Surface Meteorological Fields during Boreal Summer: A Comprehensive Analysis over North America

Abstract A series of stationary wave model (SWM) experiments are performed in which the boreal summer atmosphere is forced, over a number of locations in the continental United States, with an idealized diabatic heating anomaly that mimics the atmospheric heating associated with a dry land surface. For localized heating within a large portion of the continental interior, regardless of the specific location of this heating, the spatial pattern of the forced atmospheric circulation anomaly (in terms of 250-hPa eddy streamfunction) is largely the same: a high anomaly forms over west-central North America and a low anomaly forms to the east. In supplemental atmospheric general circulation model (AGCM) experiments, similar results are found; imposing soil moisture dryness in the AGCM in different locations within the U.S. interior tends to produce the aforementioned pattern, along with an associated near-surface warming and precipitation deficit in the center of the continent. The SWM-based and AGCM-based patterns generally agree with composites generated using reanalysis and precipitation gauge data. The AGCM experiments also suggest that dry anomalies imposed in the lower Mississippi River valley have remote surface impacts of particularly large spatial extent, and a region along the eastern half of the U.S.–Canadian border is particularly sensitive to dry anomalies in a number of remote areas. Overall, the SWM and AGCM experiments support the idea of a positive feedback loop operating over the continent: dry surface conditions in many interior locations lead to changes in atmospheric circulation that act to enhance further the overall dryness of the continental interior.

Effect of Plasticity on Shear Behavior of Low-Plasticity Fine-Grained Soil

AbstractTo study effect of plasticity on shear behavior of low-plasticity fine-grained soil, a Mississippi River Valley (MRV) silt with a plasticity index (PI) of 5.8 was treated with different dosages of sodium bentonite to modify its plasticity up to a PI of 13.5. The naturally occurring material originated from the MRV exhibited dilative behavior under normally consolidated conditions. The silt-bentonite mixtures tend to lose quasi-steady-state strength and dilative characteristics as the plasticity increased. At a PI of 13.5, the silt-bentonite mixture had plastic stress-strain clay-like behavior. Overconsolidation did not influence the friction angle of the natural silt, but for silt-bentonite mixtures with PIs of 6.2 and 9.4 the influence of prestress was evident. The normalized shear strength was significantly reduced with an increase in PI from 5.8 (natural MRV silt) to 6.0 (natural MRV silt with 2.5% bentonite added). Compared to the predictive relationships proposed by other researchers, the nor...

A Supervised Classification Method for Levee Slide Detection Using Complex Synthetic Aperture Radar Imagery

The dynamics of surface and sub-surface water events can lead to slope instability, resulting in anomalies such as slough slides on earthen levees. Early detection of these anomalies by a remote sensing approach could save time versus direct assessment. We have implemented a supervised Mahalanobis distance classification algorithm for the detection of slough slides on levees using complex polarimetric Synthetic Aperture Radar (polSAR) data. The classifier output was followed by a spatial majority filter post-processing step that improved the accuracy. The effectiveness of the algorithm is demonstrated using fully quad-polarimetric L-band Synthetic Aperture Radar (SAR) imagery from the NASA Jet Propulsion Laboratory’s (JPL’s) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). The study area is a section of the lower Mississippi River valley in the southern USA. Slide detection accuracy of up to 98 percent was achieved, although the number of available slides examples was small.

Petrographic Analysis of Late Woodland and Middle Mississippian Ceramics at the Iva Site (47Lc42), Onalaska, Wisconsin

Abstract The Iva site contained a rare effigy mound and Middle Mississippian (Ramey horizon) component within the Late Woodland Lewis phase territory of the Upper Mississippi River valley. Salvage excavations in 2002–2003 recovered fragments of numerous Angelo Punctated, Powell Plain, and Ramey Incised vessels, including examples of Angelo and Ramey in direct association. Petrographic analysis was conducted on seven grit-tempered and six shell-tempered vessels, eight of which are stylistically Mississippian. The results indicate that four of eight Mississippian vessels were likely manufactured in the American Bottom, with the other half being local imitations of Mississippian styles. These data are compared to contemporaneous Ramey horizon components in the Driftless Area of Cahokia’s northern hinterland.

Advanced Unsupervised Classification Methods to Detect Anomalies on Earthen Levees Using Polarimetric SAR Imagery.

Fully polarimetric Synthetic Aperture Radar (polSAR) data analysis has wide applications for terrain and ground cover classification. The dynamics of surface and subsurface water events can lead to slope instability resulting in slough slides on earthen levees. Early detection of these anomalies by a remote sensing approach could save time versus direct assessment. We used L-band Synthetic Aperture Radar (SAR) to screen levees for anomalies. SAR technology, due to its high spatial resolution and soil penetration capability, is a good choice for identifying problematic areas on earthen levees. Using the parameters entropy (H), anisotropy (A), alpha (α), and eigenvalues (λ, λ1, λ2, and λ3), we implemented several unsupervised classification algorithms for the identification of anomalies on the levee. The classification techniques applied are H/α, H/A, A/α, Wishart H/α, Wishart H/A/α, and H/α/λ classification algorithms. In this work, the effectiveness of the algorithms was demonstrated using quad-polarimetric L-band SAR imagery from the NASA Jet Propulsion Laboratory’s (JPL’s) Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR). The study area is a section of the lower Mississippi River valley in the Southern USA, where earthen flood control levees are maintained by the US Army Corps of Engineers.

Stratigraphy, morphology, and geochemistry of late Quaternary buried soils on the High Plains of southwestern Kansas, USA

This study investigated two stratigraphic sequences that record the complex interplay of sedimentation and pedogenesis over the past ca. 84ka on the High Plains of southwestern Kansas. Up to eight eolian sand and loess units with associated soils were identified in two cores collected from an upland setting. Soil morphological and geochemical data were used to quantitatively assess and compare soil development between multiple buried soils. Chronostratigraphic relationships indicate that 1) loess and eolian sands were episodically deposited during late Marine Isotope Stage (MIS) 5 (ca. 84–70ka), 2) the Sangamon soil at this site formed between MIS 3/4 (ca. 70–52ka), which is consistent with age estimates for renewed Sangamon pedogenesis in the Mississippi River valley, and 3) soil development in the Gilman Canyon Formation began at ca. 44ka and continued until at least 29.2ka. Multiple lines of evidence, including grain-size distributions, structure, clay content, and chemical weathering index data, indicate that the morphology and chemistry of the Ak horizon developed in the Gilman Canyon Formation is a product of cumulization by slow loess additions. Similar evidence suggests that cumulization processes are also responsible for the morphology and chemistry of other buried soils in the stratigraphic sequence. Overall, loess inputs during pedogenesis complicate the quantification of weathering processes in these soils.

Factors affecting methane emissions from rice production in the Lower Mississippi river valley, USA

Rice (Oryza sativa L.) plays a key role in sustaining global food security; however, rice production also accounts for a significant proportion of global methane (CH4) emissions, a major greenhouse gas involved in altering global climate. Many previous studies have quantified the proportion of CH4 emissions by independently evaluating factors such as soil texture and cultivars – an approach that has led to potentially biased estimates of their actual contribution to total emissions. Most of these studies have not considered the influence of the preceding crop or growing-season weather that could lead to a significant variation in carbon budgets. The main objective of this study was to identify the key edaphic, cultivar, and environmental factors and determine their proportional contributions towards CH4 emissions in direct-seeded, rice-based cropping systems. A multiple regression model was developed to quantify CH4 emissions as a function of temperature (both day and night independently and in combination) and other weather variables, soil (silt-loam-surface-textured Albaqualf and clay-surface-textured Epiaquert), cultivar (conventional and hybrid), and cropping system (rice-rice and soybean [Glycine max L.]-rice). Results showed that (i) the Albaqualf emitted 211% more CH4-C than the Epiaquert (P<0.01; (ii) inbred cultivars accounted for 55 to 70% more CH4-C emissions than hybrid cultivars (P<0.01); (iii) soybean-rice rotations produced 58% less CH4-C emissions than rice-rice rotations (P<0.01); and (iv) future warming scenarios increased CH4-C emissions by up to 53%. To mitigate CH4 emissions, future research and crop production strategies that prioritize rice production on clay-surface-textured soils and use alternatives to a rice-rice rotation are recommended.

Answer to April 2016 Photo Quiz

Answer: Fatal Pulmonary Blastomyces dermatitidis Infection. Blastomyces dermatitidis is a dimorphic fungus, endemic in the United States in the Ohio and Mississippi River valleys (1). Blastomyces most commonly causes asymptomatic pulmonary infection. However, infection may progress to acute respiratory distress syndrome (ARDS). Systemic infection may also occur, especially in immunocompromised patients.

Climatology, Synoptic Conditions, and Misanalyses of Mississippi River Valley Drylines

Abstract The dryline is an important focal point for convection initiation. Although drylines most commonly occur on the southern Great Plains, dryline passages and subsequent severe weather outbreaks have been documented in the Mississippi River valley. This study presents a 15-yr (1999–2013) climatology of these Mississippi River valley drylines and associated severe weather. Additionally, synoptic patterns are identified that may result in drylines moving atypically far eastward into the Mississippi River valley. In total, 39 Mississippi River valley drylines (hereafter referred to as MRV drylines) were identified from the North American Regional Reanalysis (NARR) dataset through the study period. Mean and anomaly synoptic composites were created for these drylines. MRV dryline events typically occur under synoptically active conditions with an amplified upper-air pattern, a 500-hPa shortwave trough to the west or northwest of the dryline, and a strong surface cyclone to the north. These boundaries are often misanalyzed or inconsistently analyzed as cold fronts, stationary fronts, or trough axes on surface maps; of the 33 cases of identified MRV drylines for which the Weather Prediction Center archived analyses were available, only 6 were correctly analyzed as drylines. Drylines moving into the Mississippi River valley often result in severe weather outbreaks in the Mississippi River valley, the Midwest, and the southeastern United States.

Petrographic Analysis of Late Woodland and Middle Mississippian Ceramics at the Iva Site (47Lc42), Onalaska, Wisconsin

The Iva site contained a rare effigy mound and Middle Mississippian (Ramey horizon) component within the Late Woodland Lewis phase territory of the Upper Mississippi River valley. Salvage excavations in 2002–2003 recovered fragments of numerous Angelo Punctated, Powell Plain, and Ramey Incised vessels, including examples of Angelo and Ramey in direct association. Petrographic analysis was conducted on seven grit-tempered and six shell-tempered vessels, eight of which are stylistically Mississippian. The results indicate that four of eight Mississippian vessels were likely manufactured in the American Bottom, with the other half being local imitations of Mississippian styles. These data are compared to contemporaneous Ramey horizon components in the Driftless Area of Cahokia's northern hinterland.

Investigating the Function of an Archaic-Period Earthwork Using Microartifacts

The functions of Archaic-period mounds in the Lower Mississippi River valley are generally poorly understood. Poverty Point's Mound C provides a unique opportunity to examine the function of one Late Archaic mound. Archaeological excavation of Mound C revealed a complex construction sequence consisting of numerous, thin, flat-topped construction stages. The presence of cultural features on the surfaces of some stages suggests these mound stage summits were used for cultural activities. The nearly complete absence of macroartifacts, however, makes it difficult to discern the types of activities undertaken on these surfaces. Microartifacts from the surfaces of these construction platforms provide an alternative perspective on the nature of activities associated with this earthwork. The analysis of microartifacts from Mound C, coupled with the limited number of macroartifacts, suggests that individual mound stage summits were intentionally cleaned prior to the addition of subsequent construction stages. The Mound C microartifact assemblages further indicate that this architectural feature was used unlike any other previously excavated context at Poverty Point.