Malcolm Williamson

An Ecosystem Restoration Model for the Mississippi Alluvial Valley Based on Geomorphology, Soils, and Hydrology

Alternating braided and meandering stream flow regimes throughout the Quaternary Period have left a subtly complex landscape of depositional features within the Mississippi Alluvial Valley (MAV). Prior to European settlement, those variations produced tremendous spatial complexity and diversity within vast forested wetlands and extensive fire-maintained prairies and savannas, with the distribution of specific plant communities largely reflecting abiotic site characteristics such as geomorphology, soils, and hydrology. Agricultural development, river engineering, flood protection, and drainage projects over the past century have destroyed most of the natural vegetation and obscured the patterns of plant community distribution. Recent studies have established hydrogeomorphic criteria for wetland classification over a large part of the MAV. Detailed, spatially explicit geomorphology and soils data are available for the entire MAV, and hydrologic mapping has been completed in many areas. Thus, even in areas that are currently in agriculture, the tools exist to adapt the hydrogeomorphic classification and to develop maps of potential plant community distribution based on abiotic characteristics of sites. These Potential Natural Vegetation maps provide an indication of the multi-scale complexity that once characterized the MAV, and serve as planning tools for ecosystem restoration.

LIDAR-based characterization and conservation of the first theropod dinosaur trackways from Arkansas, USA

LIDAR-based analyses of the first theropod dinosaur trackways known from the state of Arkansas, USA are reported. The trackways were found on a limestone bedding plane in the Albian De Queen Formation in an active gypsum quarry. Because limited access precluded thorough field study, fieldwork focused on preserving the entire site digitally with ground-based LIDAR, and detailed measurements were later taken digitally from point cloud data. The site contains eight tridactyl trackways associated with sauropod trackways and numerous isolated tracks. Although there appear to be two different tridactyl morphotypes, we show that the tracks are all likely from a single species of trackmaker. We apply a simple method of estimating substrate consistency by comparing the differences between true track dimensions and apparent track dimensions. The tridactyl tracks at the southern end of the site are preserved with significantly greater differences in true vs. apparent dimensions and are shallower than the rest of the tridactyl tracks at the site, which we interpret as the result of outward expansion of the soft tissues of the foot upon contact with a firm substrate. We interpret the firm substrate as having high bulk density and high shear strength, which also explain associated manus-only sauropod tracks. We show that the tridactyl tracks are likely from theropod trackmakers and that footprint lengths, trackway paces, stride lengths, and pace angulations of the De Queen trackways are statistically indistinguishable from equivalent measurements of theropod trackways in the Glen Rose Formation. The Glen Rose tracks are attributed to the large-bodied theropod, Acrocanthosaurus and we likewise attribute the De Queen tracks to Acrocanthosaurus, which is known from skeletal remains in temporally equivalent units and from the mine itself.

Assessing the Impact of Hydraulic Fracturing on Water Resources in the Fayetteville Shale Area (Arkansas, USA)

Natural gas production in the Fayetteville shale area (Arkansas, USA) might create critical levels of water discharge due to diversion of surface water used for horizontal hydraulic fracturing. In fact, each well requires between 12000 m3 and 26500 m3 of water for hydraulic fracturing and the number of wells is expected to grow in the future. This usage, combined with drinking and farming needs, could pose water resource management concerns.

Probabilistic Risk Based Decision Support for Oil and Gas Exploration and Production Facilities in Sensitive Ecosystems

This report describes work performed during the initial period of the project “Probabilistic Risk Based Decision Support for Oil and Gas Exploration and Production Facilities in Sensitive Ecosystems.” The specific region that is within the scope of this study is the Fayetteville Shale Play. This is an unconventional, tight formation, natural gas play that currently has approximately 1.5 million acres under lease, primarily to Southwestern Energy Incorporated and Chesapeake Energy Incorporated. The currently active play encompasses a region from approximately Fort Smith, AR east to Little Rock, AR approximately 50 miles wide (from North to South). The initial estimates for this field put it almost on par with the Barnett Shale play in Texas. It is anticipated that thousands of wells will be drilled during the next several years; this will entail installation of massive support infrastructure of roads and pipelines, as well as drilling fluid disposal pits and infrastructure to handle millions of gallons of fracturing fluids. This project focuses on gas production in Arkansas as the test bed for application of proactive risk management decision support system for natural gas exploration and production. The activities covered in this report include meetings with representative stakeholders, development of initial content and design for an educational web site, and development and preliminary testing of an interactive mapping utility designed to provide users with information that will allow avoidance of sensitive areas during the development of the Fayetteville Shale Play. These tools have been presented to both regulatory and industrial stakeholder groups, and their feedback has been incorporated into the project.