DeGray Lake Research Articles

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EDUCATION Reactions ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2022, 100 (16), p 5May 9, 2022Cite this:C&EN 100, 16, 5Letters to the editorMemorizing the periodic tableRe: Newscripts, April 18, 2022, page 40Some years ago at the University of North Carolina at Chapel Hill, I taught a one-semester inorganic course for BS chemistry majors. During the class we covered all the noncarbon elements in a systematic way, illustrating group relationships. The periodic table was our map, and a giant version hung above the blackboard for reference.At the end of the semester and as a part of the final exams, I covered the chart and passed out blank periodic tables for the students to fill in the chemical symbol of each element in its appropriate place. Every correct answer (up to 100) added a point to their final grade.The average score was about 50, heavily skewed to the s- and p-block elements. Only a few diligent students got more than a couple of the rare earths in their proper places.I agree with Martin Galpin at the University of Oxford that chemistry students need to understand elements’ place in the periodic table.Philip RakitaPhiladelphiaBromine sourcesI am responding to a letter to the editor (C&EN, March 28, 2022, page 3) that was a response to the eagle-killing aetokthonotoxin article (C&EN, Feb. 28, 2022, page 6). Wallace Fu asked in his letter, “Where does the hydrilla find bromine to incorporate into this toxin?” He goes on to postulate that the likely source is from “minerals in the ground or freshwater lakes in Arkansas.” I believe he is correct! Wallace goes on to refer to the situation as an “environmental disaster” that could also “affect the health of our domestic animals and humans.” It turns out there is a lot of bromine in Arkansas. In fact, one of the bromine extraction hot spots in the US is a mine in Arkansas south of DeGray Lake. But, if the bromine is naturally occurring, can we really consider that an environmental disaster? Wallace should be doubly concerned in this particular case since another region with a history of bromine extraction is his home state of Michigan.Ken SavinIndianapolis CorrectionsAug. 24, 2020, page 8: The paper that was the basis of a news article on an iridium catalyst’s functionalization of remote C–H bonds has been retracted (Science 2022, DOI: 10.1126/science.abq4856).April 18, 2022, page 28: The cover story about radioconjugates incorrectly describes indium-111. It is a ɣ emitter, not a positron emitter.April 25, 2022, page 5: The news article on buckyballs in ethylene glycol synthesis incorrectly describes C60’s role in solar cells. The fullerene acts as an electron acceptor, not an electron buffer, in that context.

An integrated chemo-and sequence-stratigraphic framework of the Early Pennsylvanian deepwater outcrops near Kirby, Arkansas, USA, and its implications on remnant basin tectonics

The Jackfork Group in Arkansas, U.S.A. is a major ‘training ground’ for academics, students, and petroleum industry geoscientists interested in deep water exploration and development. Several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks. The Kirby sections in western Arkansas provide a unique opportunity to build a complete and continuous sequence stratigraphic framework for Early Pennsylvanian time in the ancient Ouachita Basin. There are 25 outcrops, including 12 roadcuts on Highway 27, and 13 measured sections in the Baumgartner Quarry. All the measurements and interpretations on the outcrops were integrated with previous work using modern concepts of deepwater turbidite geology, including (1) regional tectonic and sequence stratigraphic framework of the Stanley Group, Jackfork Group, and Johns Valley Shale in the Ouachita Basin, (2) deepwater outcrop characterization and correlation from the DeGray Lake Section, Dierks Section and Big Rock Quarry which are on the trend of the depositional fairway, (3) chemostrata data from key shale layers which are considered as potential correlative condensed sections.Twenty-five key shale samples from Kirby, DeGray and Dierks sections have been tested using Inductively Coupled Plasma and Mass Spectrometry (ICP-MS) tests. An additional 525 samples were later collected for Handheld X-Ray Fluorescence (XRF) tests for both major and trace elements. Results of sequence and chemostrata analysis indicate that the entire Kirby sections consist of at least three 3rd order sequences from the bottom of the Jackfork Group to the middle of the Johns Valley Group, and over ten 4th order sequences caused by a combined effect of tectonic uplift, eustatic sea-level change, mixed sediment provenance and shifting of depositional fairways when the Ouachita Basin was transitioning from a passive margin to a remnant marine basin. Rare Earth and Trace Element results are compared with known tectonic data to further pinpoint the tectonic environment of the Ouachita Basin during early Pennsylvanian time, which is dominantly a continental arc setting.

Certain Caddo Sites in the Ouachita Mountains of Southwestern Arkansas

In the last few years, we have had the opportunity to study a number of prehistoric Caddo Indian sites in the Ouachita Mountains of southwestern Arkansas through conducting archeological surveys of more than 2700 acres at three lakes constructed and managed by the U.S. Army Corps of Engineers, Vicksburg District. The three lakes are DeGray Lake on the Caddo River, Lake Ouachita on the Ouachita River, and Lake Greeson on the Little Missouri River. Our purpose in this article is to summarize the archeological character of the prehistoric Caddo sites in these three different parts of the Ouachita Mountains. We focus in particular on the material culture record of these prehistoric Caddo settlements—especially on the ceramic sherds found on them—and discuss when these sites may have been occupied by Caddo peoples.

Experimental vacuolar myelinopathy in red-tailed hawks.

Avian vacuolar myelinopathy (AVM) was recognized in 1994 as a cause of wild bird mortality when 29 bald eagles (Haliaeetus leucocephalus) succumbed to the disease at DeGray Lake, Arkansas (USA). The cause of AVM and its source remain undetermined despite extensive diagnostic and research investigations. Two years later, when AVM killed 26 eagles in the same area in Arkansas, it became apparent that American coots (Fulica americana) had identical neurologic signs and lesions, and it was hypothesized that eagles acquired AVM via ingestion of affected coots. In order to test this hypothesis, we fed coot tissues (brain, liver, kidney, muscle, fat, and intestinal tract) to rehabilitated, non-releasable red-tailed hawks (Buteo jamaicensis). Five hawks received tissues from coots with AVM lesions, and one hawk received tissues from coots without brain lesions that had been collected at a site where AVM never has been documented. All hawks received 12-70 g/day (mean = 38 g) of coot tissues for 28 days. All six hawks remained clinically normal during the study. The birds were euthanatized on day 29 and microscopic lesions of AVM were found in all hawks that received tissues from affected coots, but not in the hawk that received tissues from unaffected coots. This marks the first time that AVM has been produced in birds under laboratory conditions and proves that birds of prey can acquire AVM via ingestion of tissues from affected coots.

Lateral Correlation Trends in Bedded and Massive Turbidites, with an Example From De Gray Lake, Arkansas

Lateral Correlation Trends in Bedded and Massive Turbidites, with an Example From De Gray Lake, Arkansas

Correlation Trends in Thin-Bedded Turbidites, Jackfork Sandstone, DeGray Lake, Arkansas

Michael B. De Vries and Arnold H. Bouma The methods of data collection for modern and ancient turbidite systems are necessarily different. Therefor, the integration of data sets from modern and ancient turbidite systems is desirable if lithofacies and surface morphological models are to be linked. To achieve this, two activities have to be dealt with: 1) Modern and subsurface turbidite systems must be extensively cored and described, and 2) outcrops in ancient turbidite systems must be correlated laterally in sufficient detail to establish a framework to facilitate the interpretation of subenvironments which build the turbidite system. The latter approach can be accomplished only in a few turbidite systems that are relatively well exposed, with outcrops exposing thick sections of turbidites which have an equally thick correlative. One ancient turbidite system meeting the above criteria is the Pennsylvanian Jackfork Group exposed around DeGray Lake, Arkansas. Two correlatable outcrops form the east and west wall of the Spillway, 214 feet (65 m) apart, while the third outcrop is 5500 feet (1675 m) to the west near the intake for the power-generating dam. Each outcrop was divided into lithofacies-based units and each unit was described in general terms and individual beds in each unit were measured. The lithofacies-based units established a rough correlation between large segments of each outcrop using changes in character. A more detailed assessment and quantification of these changes is then produced when dividing the units into smaller subunits. Stratigraphically thick sections of individual beds can often be correlated between Spillway walls. It is difficult to accomplish this using lithologic logs derived from measured sections. It is easier to plot the sandstone bed thickness values on a graph such as shown in Figure 1. Each successive bed is weighted the same on the vertical scale with the horizontal scale representing bed thickness. The thinner beds, represented by the left-deflecting spikes, show no characteristic pattern and do not necessarily follow the same trend as the thicker beds, represented by the right-deflecting spikes. The thicker beds can be divided into thickening-upward, thinning-upward and symmetrical successions of beds which may be called cycles. These cycles form distinctive patterns for each outcrop and unit. Pattern recognition can be used to correlate cycles from each outcrop similar to the correlation of subsurface well-logs. Individual beds which make up each cycle can then be correlated across the Spillway. This method allows for important lithofacies changes and thinning trends to be recognized. The lower one-third (approx. 140 feet [42 m] thick) of the Spillway section overlies massive channel deposits. The thinningand fining-upward nature of these beds and their position over channel deposits make these interpretable as a channel-levee-overbank succession. Paleocurrent direction for the channels in this part of the Jackfork Group is westerly. Detailed correlation of individual beds, using a plot similar to Figure 1, reveals an increasing degree of correlatability upward, from 40% in the lower part to over 80% in the upper part of the section. This increase may reflect more laterally extensive, sheet-type flow deposition. The second section is relatively thick-bedded and is sandwiched between very thin-bedded distal overbank deposits. This section is interpreted as a depositional lobe deposit. Mostly thickening-upward cycles can be recognized and used for correlation between Spillway walls. Individual bed and cycle thicknesses for each cycle show thinning trends across the Spillway which switch back and forth in direction, compatible to compensation cycles. A correlative section of turbidites, which were measured at the Intake, also shows thickening-upward trends. The overall thickness of this section is about 51 feet (16 m) thick while the Spillway sections are much thicker at about 80 feet (42 m) thick. Paleocurrent directions measured from sole markings show that this section is slightly oblique to directly down-current of the Spillway. Figure 1 shows good overall correlation between Spillway sections and the Intake section, but relatively poor bed-to-bed correlatability. The third section is 14 feet (4 m) thick and comprises thicker-bedded turbidites which are thinning-upward and are sandwiched between very thin-bedded basin plain or distal overbank deposits. This section is interpreted as a small channel deposit. The thicker beds typically split into several low angle amalgamations. A correlative section at the Intake is slightly thicker, but is thinner-bedded and shalier. As in all sections, the original correlation was based upon lithofacies. The thickness plot for this section shows that the beds included in the overbank deposits at the Spillway can be correlated with Louisiana State University, Department of Geology and Geophysics, Baton Rouge, Louisiana 70803

Application of Two‐Dimensional Water Quality Model

A two‐dimensional, laterally averaged, finite‐difference hydrodynamic and transport water quality model was applied to DeGray Lake, Arkansas, a reservoir extensively studied by the U.S. Army Corps of Engineers. The reservoir was known to exhibit strong longitudinal and vertical gradients in water quality, while lateral variations were generally small. DeGray Lake exhibited dissolved oxygen declines in the metalimnion of the main pool and hypolimnion of headwater regions during summer and fall months. Field data from two separate years were used to calibrate and verify the model. Spatial and temporal variations in dissolved oxygen concentrations and other water quality variables were successfully predicted throughout the stratification cycles.

Seasonal and longitudinal variations in apparent deposition rates within an Arkansas reservoir1

Seasonal and spatial differences in apparent sediment trapping rates were related to the establishment of longitudinal gradients in water quality at DeGray Lake, Arkansas. Gradients in turbidity developed during winter and spring due to high suspended loads, which settled primarily in the headwater region. Gradients in apparent deposition of allochthonous organic carbon and chlorophyll a also influenced detrital processing and hypolimnetic dissolved oxygen conditions. Hypolimnetic dissolved oxygen depletion started in May in the headwater region, due to a high volumetric dissolved oxygen demand, and spread slowly to the dam by winter. These patterns indicated that riverine inputs and deposition influenced biological activity along the longitudinal axis of the lake.

A COMPARISON OF RESERVOIR OXYGEN PREDICTIONS FROM ONE-AND TWO-DIMENSIONAL MODELS

ABSTRACT The U.S. Army Corps of Engineers has developed one-and two-dimensional models as tools for water resources management. CE-QUAL-R1 is a variable-layer, horizontally averaged water quality model. CE-QUAL-W2 is a two-dimensional (laterally averaged) finite-difference hydro-dynamic and transport water quality model. The water quality algorithms in both models are similar and both have been applied to DeGray Lake, Ark., a reservoir that has been extensively studied by the Corps of Engineers. The reservoir is of particular interest because of dissolved oxygen declines in the metalimnion of the main pool during summer and fall months. Both models successfully predict spatial and temporal variations in dissolved oxygen concentrations in their respective dimensions. Evaluations were made of all flux values contributing to simulated oxygen dynamics.

Flux Use for Calibrating and Validating Models

Predicted flux, or process rates, must be considered along with predicted state variables when calibrating or validating water quality models. Concentrating only on changes of state variables and ignoring predicted fluxes could result in the implementation of inappropriate management strategies. To illustrate this, the Corps of Engineers' one‐dimensional reservoir water quality model, CE‐QUAL‐R1, was calibrated using data collected at DeGray Lake, Arkansas. Initial predictions of dissolved oxygen, using coefficient values obtained from the literature, were not satisfactory. Evaluation of the flux predictions for oxygen showed which processes were most important in regulating dissolved oxygen, and showed those that were incorrect when compared to measured values. During the ensuing calibration simulations, as the flux predictions were brought more in line with measured values, the predictions of dissolved oxygen improved markedly.

Lateral Continuity of Turbidite Lithofacies Within Pennsylvanian Jackfork Group Near DeGray Lake, Clark County, Central Arkansas: ABSTRACT

A 23-km long, 2.5-km wide area with excellent exposures of the Jackfork Group occurs on and near the southern shore of DeGray Lake. This area, despite moderate to heavy vegetative cover, offers an opportunity to study the lateral extent of turbidite and associated submarine-fan lithofacies and to develop a model for estimating the extent of subsurface turbidite reservoirs using data from one or more wells. The extent of arenaceous lithofacies in the study area is also important to the local stone-quarrying industry. Over 1,000 m of published and newly measured stratigraphic sections were studied to determine lithofacies present using the 1978 classification system of E. Mutti and F. Ricci-Lucchi. Lithofacies were then correlated along strike (which is generally within 20° of paleocurrent heading) using stratigraphic correlations, aerial photographs, field checking, and field tracing of nearly continuous outcrops. Sandy sequences in which lithofacies B or C predominate, but which may contain lithofacies A, form ridges. These ridges are especially prominent where arenaceous intervals reach 10-30 m in thickness. Individual beds within these intervals are nearly all less than 1.2 m thick and are difficult to trace laterally. The arenaceous intervals, however, can be traced as units for up to 6 km and correlated for up to 8 km or more along strike. Shaly stratigraphic sequences of lithofacies G, D, E, and, rarely, F are poorly exposed, but can be correlated along strike for up to 6.5 km, with topographic expression and vertical lithofacies sequence being important guides. End_of_Article - Last_Page 240------------

LAKE-RIVER INTERACTIONS: IMPLICATIONS FOR NUTRIENT DYNAMICS IN RESERVOIRS

ABSRACT Unlike small drainage lakes which receive nutrient inputs from relatively diffuse sources, reservoirs and other river-fed lakes receive a majority of their nutrient income from a single large source located distant from the lake's outlet. Interactions between lake and river, which are governed by hydrology, the thermal structure of the lake, and lake morphology, will, therefore, play an important role in determining the impact and ultimate fate of influent nutrients. These interactions may also affect the manner in which nutrients are recycled and/or distributed within the reservoir or river-fed lake and lead to the establishment of longitudinal gradients in concentration. Studies conducted at DeGray Lake, Ark., and West Point Lake, Ga., both large Corps of Engineers hydropower reservoirs, provide instructive examples of some of the effects of these interactions. Both lakes exhibit longitudinal gradients in nutrient and chlorophyll concentrations which are influenced by the hydrologic characterist...

VERIFICATION OF THE RESERVOIR WATER QUALITY MODEL, CE-QUAL-R1, USING DAILY FLUX RATES

ABSTRACT Emphasis on evaluation techniques where measured versus predicted changes of mass are compared can produce a model that predicts the correct answers for the wrong reasons. The movement of mass between compartments (flux) should be compared to measured flux as part of the model verification. Model verification techniques need to reflect the same level of resolution inherent in the model structure. The U.S. Corps of Engineers water quality model, CE-QUAL-R1, was verified for DeGray Lake, Ark., using this procedure. Several processes important in determining the mass of the constituents were measured for DeGray Lake. Primary production rate and settling rates of algae, total dry weight, and organic matter were compared to predicted fluxes. Results indicated that the model was satisfactory in predicting trends in flux values.

Correlation of total organic carbon and dry weight data as indices of fresh-water zooplankton biomass

Preserved zooplankters from DeGray Lake, Arkansas, U.S.A., were separated from other net seston by density-gradient centrifugation, washed, dried, and weighed. Total organic carbon (TOC) content of zooplankters was determined from carbon analysis involving wet persulfate oxidation. Dry weight and TOC data were highly correlated (r2 = 0.9649; P < 0.001) when subjected to a step-wise procedure of the Statistical Analysis System (SAS). The model is represented by the equation log Y =1.14 log X + 0.46, where X = TOC and Y = dry weight. Carbon averaged 30.33 ± 9.86 (S.D.)% of dry weight.

RESERVOIR WATER QUALITY SAMPLING DESIGN1

ABSTRACT: The design of monitoring programs often serves as one of the major sources of error or uncertainty in water quality data. Properly designed programs should minimize uncertainty or at least provide a means by which variability can be partitioned into recognizable components. While the design of sampling programs has received recent attention, commonly employed strategies for limnological sampling of lakes may not be completely appropriate for many reservoirs. Based on NES data, reservoirs are generally larger, deeper, and morphologically more complex than natural lakes. Reservoirs also receive a majority of their inflow from a single tributary located a considerable distance from the point of outflow. The result is the establishment of marked physical, biological, and chemical gradients from headwater to dam. The existence of horizontal as well as vertical gradients, and their importance in water quality sampling design were the subject of intensive transect sampling efforts at DeGray Lake, a U.S. Army Corps of Engineers reservoir in southern Arkansas. Data collected were used to partition Variance, identify areas of similarity, and demonstrate how an equitable sampling program might be designed.

Biomass Model of Reservoir Fish and Fish-food Interactions, with Implications for Management

A mathematical model was developed to help evaluate trophic relations of fishes in reservoirs and to assess the effects of perturbations (e.g., reservoir operations, species introductions, stocking, and harvest) on reservoir ecosystems. The model estimates the production and food requirements of five functional groups of fish biomass, established according to the food supporting each group-(1) plants and detritus, (2) benthos, (3) zooplankton, (4) fish, and (5) terrestrial invertebrates. When applied to data collected from 1977 to 1980 in DeGray Lake, Arkansas, the model revealed that the biomass of fish supported by diets of plants and detritus (BSPD) was positively correlated with precipitation within and among years. The BSPD, expressed as a percent of the total standing crop, declined significantly from 1974 to 1977 and then stabilized at a low level from 1977 to 1980. In 1979, primary production was insufficient to sustain zooplankton production and BSPD from June to mid-August, and from late September to early October. The mean monthly biomass of benthos, estimated from food requirements of benthophagous fish, was within the range of published weights. Production of zooplanktivorous fish was limited by declining zooplankton production in late summer, and piscivore production was limited by the availability of prey fish in early spring and late summer.