ABSTRACTS
Carbonates & Evaporites
Volume 17, Number 2, 2002, December
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KARST IN EVAPORITE ROCKS OF THE UNITED STATES
Kenneth S. Johnson
Oklahoma Geological Survey, 100 E. Boyd, Room N-131, Norman, Oklahoma 73019, U.S.A.; [email protected]
ABSTRACT: Evaporites are the most soluble of common rocks; they are dissolved readily to form the same range of karst features that typically are found in limestones and dolomites. Evaporites, including gypsum (or anhydrite) and salt, are present in 32 of the 48 contiguous United States, and they underlie about 35-40% of the land area. Evaporite outcrops typically contain sinkholes, caves, disappearing streams, and springs. Other evidence of active karst in evaporites includes surface-collapse features and saline springs or saline plumes that result from dissolution of salt. Many evaporites, including some in the deeper subsurface, also contain evidence of paleokarst that is no longer active; this evidence includes dissolution breccias, breccia pipes, slumped beds, and collapse structures. Evaporites occur in 24 separate structural basins or geographic districts in the United States, and either local or extensive evaporite karst is known in almost all of these basins or districts. Human activities also have caused development of evaporite karst, primarily in salt deposits. Boreholes or underground mines may enable (either intentionally or inadvertently) unsaturated water to flow through or against salt deposits, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures can cause land subsidence or catastrophic collapse. Evaporite karst, both natural and human-induced, is far more prevalent than commonly believed.
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MCCAULEY SINKS: A COMPOUND BRECCIA PIPE IN EVAPORITE KARST, HOLBROOK BASIN, ARIZONA, U.S.A.
1James T. Neal and 2Kenneth S. Johnson
1Adjunct Curator of Geology, Sharlot Hall Museum, 415 W. Gurley Street, Prescott, Arizona 86305
2Emeritus Associate Director, Oklahoma Geological Survey, 100 E. Boyd, Room N-131, Norman, Oklahoma 73019
ABSTRACT: The McCauley Sinks, in the Holbrook basin of northeastern Arizona, are comprised of some 50 individual sinkholes within a 3-km-wide depression. The sinks are grouped in a semi-concentric pattern of three nested rings. The outer ring is an apparent tension zone containing ring fractures. The two inner rings are semi-circular chains of large sinkholes, ranging up to 100 m across and 50 m deep. Several sub-basins within the larger depression show local downwarping and possible incipient sinkholes.
Permian Kaibab Formation limestone is the principal surface lithology; the limestone here is less than 15 m thick and is near its easternmost limit. Although surface rillenkarren are present, and the sinks are seen in the Kaibab limestone outcrops, the Kaibab is mainly a passive rock unit that has collapsed into solution cavities developed in underlying salt beds. Beneath the Kaibab is Coconino Sandstone, which overlies the Permian Schnebly Hill Formation, the unit containing the evaporite rocks - principally halite in the Corduroy Member. Evaporite karst in this part of the Holbrook basin is quite different from the eastern part, probably because of the westward disappearance of the Holbrook anticline, a structure that has major joint systems that help channel water down to the salt beds farther to the east. Also, the McCauley Sinks are near the western limits of the evaporites.
The structure at McCauley Sinks suggests a compound breccia pipe, with multiple sinks contributing to the inward-dipping major depression. The Richards Lake depression, 5 km southeast of McCauley Sinks, is similar in form and size but contains only a single, central sinkhole. An apparent difference in hydrogeology at McCauley Sinks is their proximity to the adjacent, deeply incised, Chevelon Canyon drainage, but the hydrologic connections are unknown.
The 3-km-wide McCauley Sinks karst depression, along with five other nearby depressions, provide substantial hydrologic catchment. Because of widespread piping into karst features and jointed bedrock at shallow depth, runoff water does not pond easily at the surface. There appears to be a greater recharge efficiency here than in alluvial areas; thus concern exists for groundwater users downgradient from the karst area. Accordingly, sinkholes and open fissures should not be used for waste disposal.
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SPELEOLOGY OF GYPSUM CAVES IN OKLAHOMA
John Bozeman and Susan Bozeman
Central Oklahoma Grotto, NSS, 2624 Chaucer Drive, Oklahoma City, Oklahoma 73120, USA; [email protected]
ABSTRACT: The gypsum caves of western Oklahoma are situated in three separate areas of evaporite karst: (1) the Cimarron Gypsum Hills, in the northwest, along the Cimarron River; (2) the Weatherford Gypsum Hills, in west-central Oklahoma, to the north of the Wichita Mountains; and (3) the Mangum Gypsum Hills, in the southwest, west of the Wichita Mountains. Caves of the Cimarron Gypsum Hills and the Mangum Gypsum Hills are developed in the alternating dolomite, gypsum/anhydrite, and shale beds of the Permian Blaine Formation. Ranging from natural bridges to extensive cave systems, the largest is the 10 km of passages in Jester Cave in the Mangum Gypsum Hills. Cave passages formed in the normally paired gypsum and dolomite beds exhibit narrow (1.5-5 m wide), sinuous, canyon-like profiles. The development of broader passages, with widths from 5 m to more than 35 m, involve the shale beds. Some are bedding-plane passages with extremely low ceilings, whereas others are comfortable, walking-height passages with ceilings from 3-15 m high. The Blaine Formation, in the area of humanly mappable cave development, is from 12 m to approximately 50 m thick. The caves drain the bluffs/escarpments and normally end in karst spring resurgences. Roof collapse often modifies these resurgences into breakdown mazes. The Weatherford Gypsum Hills caves are formed in the Permian Cloud Chief Formation. The Cloud Chief gypsum is chalkier than the Blaine gypsums and the resultant cave development is more segmented, ranging from natural bridges (1.5-15 m in length) to cave segments (locally referred to as "tunnels") that are tens of meters to more than one kilometer in length. These caves exhibit very little vertical development, and none of the bedding-plane development found in the Blaine Formation.
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ENVIRONMENTAL PROBLEMS CAUSED BY GYPSUM KARST AND SALT KARST IN GREAT BRITAIN
Anthony H. Cooper
British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK.
ABSTRACT: In Great Britain, gypsum karst is widespread in the Late Permian (Zechstein) gypsum of north-eastern England. Here and offshore, a well-developed palaeokarst with large breccia pipes was formed by dissolution of the underlying Permian gypsum. Farther south, around Ripon, the same rocks are still being dissolved, forming an actively evolving phreatic gypsum-maze cave system. This is indicated by the presence of numerous active subsidence hollows and sulphate-rich springs. In the English Midlands, gypsum karst is locally developed in the Triassic deposits south of Derby and Nottingham. Where gypsum is present, its fast rate of dissolution and the collapse of overlying strata lead to difficult civil-engineering and construction conditions; these can be further aggravated by water abstraction. Salt (halite) occurs within British Permian and Triassic strata, and has a long history of exploitation. The main salt fields are in central England and the coastal areas of northwest and northeast England. In central England, saline springs indicate that rapid, active dissolution occurs that can cause subsidence problems. In the past, subsidence was aggravated by shallow mining and the uncontrolled extraction of vast amounts of brine. This has now almost stopped, but there is a legacy of unstable buried salt karst, formed by both natural and induced dissolution. The buried salt karst occurs at depths ranging from about 40 m to 130 m; above these depths, the overlying strata are foundered and brecciated. In the salt areas, construction and development are hampered by both abandoned mines and by natural or induced brine runs, with their associated unstable ground.
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PALEOSUBSIDENCE AND ACTIVE SUBSIDENCE DUE TO EVAPORITE DISSOLUTION IN SPAIN
1Francisco Gutiérrez, 2Federico Ortí, 1Mateo Gutiérrez, 3Alfredo Pérez-González, 4Gerardo Benito, 5F. Javier Gracia, and 6Juan José Durán
1University of Zaragoza,Geodinámica; Edificio Geológicas; C. Pedro Cerbuna, 12; 50009, Zaragoza; Spain; [email protected]; Fax: 34-976-761088; Phone: 34-976-761090
2University of Barcelona, Departamento de Petrología, Geoquímica y Prospección Geológica; Facultad de Geología; Universidad de Barcelona; Zona Universitaria de Pedralbes; 08028
Barcelona; Spain; [email protected]; Fax: 34-93-4021340;Phone: 34-93-4021408
3University Complutense of Madrid,Departamento de Geodinámica; Facultad de Geológicas; Universidad Complutense; 28040 Madrid; Spain; [email protected]; Fax: 34-91-3944845; Phone: 34-91-3944890
4Centro de Estudios Medioambientales, CSIC, Madrid, Centro de Ciencias Medioambientales (C.S.I.C.); C. Serrano 115dpdo.; 28006 Madrid; Spain; [email protected]; Fax: 34-91-5640800; Phone: 34-91-5625020; ext.: 213
5University of Cádiz, Facultad de Ciencias del Mar; Universidad de Cádiz; 11510 Puerto Real; Cádiz; Spain; [email protected]; Fax: 34-956-016040; Phone: 34-956-016168
6Instituto Tecnológico y Geominero de España, Madrid, Instituto Tecnológico y Geominero de España; C. Rios Rosas, 23; 28003 Madrid; Spain; [email protected];
[email protected];Fax: 34-91- 3495742; Phone: 34-91-3495852
ABSTRACT: Evaporite formations crop out or are at shallow depth present in an extensive area of Spain. These soluble sediments occur in diverse geological domains and were deposited over a long time span, from the Triassic up to the present day. Broadly, the Mesozoic and Paleogene formations (Alpine cycle) are affected by compressional structures, whereas the Neogene (post-orogenic) sediments remain undeformed. Subsidence caused by subsurface dissolution of evaporites (subjacent karst) takes place in three main types of stratigraphic settings: a) subsidence affecting evaporite-bearing Mesozoic and Tertiary successions (interstratal karst); b) subsidence in Quaternary alluvial deposits related to the exorheic evolution of present-day fluvial systems (alluvial or mantled karst); and c) subsidence in exposed evaporites (uncovered karst). These types may be represented by paleosubsidence phenomena (synsedimentary and/or postsedimentary) recognizable in the stratigraphic record, or by equivalent, currently active or modern examples which have a surface expression. Interstratal karstification of Mesozoic marine evaporites, and the consequent subsidence of overlying strata, is revealed by stratiform collapse breccias and wedge outs of the evaporites grading into unsoluble residues. In several Tertiary basins, the sediments overlying evaporites locally show synsedimentary and/or postsedimentary subsidence structures. Dissolution-induced subsidence coeval with sedimentation is accompanied by local thickening of strata in basin-like structures with convergent dips and cumulative wedge-out systems. This sinking process controls the generation of depositional environments and lithofacies distribution. Postsedimentary subsidence produces a great variety of gravitational deformations in Tertiary supra-evaporitic units, including both ductile and brittle structures (flexures, synforms, fractures, collapse, and brecciation). Quaternary fluvial terrace deposits overlying evaporites show anomalous thickenings (>150 m) caused by a dissolution-induced subsidence process in the alluvial plain, which is balanced by alluvial aggradation. The complex evolution (in time and space) of paleosubsidence leads to intricate and chaotic structures in the alluvium, which may be erroneously interpreted as pure tectonic deformations. The current subsidence and generation of sinkholes due to suballuvial karstification constitutes a geohazard which affects large, densely populated areas, and thus endangers human safety and poses limitations on development. An outstanding example can be seen in Calatayud, an important historical city where subsidence has severely damaged highly valuable monuments. Subsidence resulting from the underground karstification of evaporites has caused or influenced the generation of some important modern lacustrine basins, such as Gallocanta, Fuente de Piedra, and Banyoles Lakes. The sudden formation of sinkholes due to collapse of cave roofs is fairly frequent in some evaporite outcrops. Very harmful and spectacular subsidence activity is currently occurring in the Cardona salt diapir, where subsidence has been dramatically exacerbated by mining practices.
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GYPSUM KARST IN THE BETIC CORDILLERA (SOUTH SPAIN)
1J.M. Calaforra, 1A. Pulido-Bosch, and 2M. Lopez-Chicano
1 Department of Hydrogeology, University of Almería, 04120 Almería (Spain)
2Department of Geodynamics, University of Granada, 18071 Granada (Spain)
ABSTRACT: Among the numerous karstified gypsum outcrops of the Betic Cordillera, in this article we present three extreme examples, with markedly different origins and development: (1) the Antequera gypsum karst, where diapiric phenomena have had a decisive influence on the geomorphological and hydrogeological evolution of the area; (2) the karst in gypsum of Vallada, with its processes of hyperkarstification of gypsum caused by the presence of significant quantities of halite; and (3) the Sorbas gypsum karst, where a complex speleogenetic development is demonstrated by a succession of vadose and phreatic passages within a multilayer aquifer. In these three cases, we have considered the geomorphological evolution of gypsum karst based on hydrogeological information gathered in each of the outcrop areas in a way which integrates both aspects into a more generalized speleogenetic model.
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GYPSUM KARST IN THE WESTERN UKRAINE: HYDROCHEMISTRY AND SOLUTION RATES
Klimchouk, A.B. and Aksem, S.D.
Institute of Geological Science, Natl. Acad. of Sciences, Kiev, Ukraine, P.O.Box 136, Kiev-01030, Ukraine; [email protected]
ABSTRACT: Gypsum karst in the western Ukraine underlies a large territory of more than 20,000 km2 and is represented by a range of stages (evolutionary types), from deep-seated through subjacent to entrenched. Correspondingly, hydrogeological settings of karst development, circulation patterns, and chemical characteristics of groundwaters differ substantially between the respective areas. Based on 1,800 analyses, the paper summarises hydrochemistry of the gypsum-hosting Miocene aquifer. Most of the sampling has been performed in conjunction with a regime study of gypsum-solution rates by means of standard tablets. This study included 53 tablet stations representing varying conditions of water-rock interaction, where 644 weight-loss measurements have been made during 1984-1992. The highest rates are characteristic of entrenched karst, although active dissolution there is localised along well-defined sinking streams with short underground courses, rare vertical-percolation paths, and the water table. Lower, but still quite substantial, rates are characteristic for subjacent and deep-seated (confined) karst. However, the overall dissolution removal is higher there, due to higher rates of flow through the gypsum and the larger area of rock/solvent contact. The results are generalised in order to derive the approximate solution rates that characterise major situations and that are suitable for modeling purposes.
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HUMAN-INDUCED ACTIVATION OF GYPSUM KARST IN THE SOUTHERN PRIANGARIA (EAST SIBERIA, RUSSIA)
Yu. B. Trzhtsinsky
Institute of the Earth's Crust, Siberian Department, Russian Academy of Sciences, Russia
ABSTRACT: Over 25% of the area of the Siberian Platform is composed of carbonate, sulphate, and saline rock deposits that are marked by intensive karstification and leaching. Particularly intensive karst occurs under natural conditions within gypsiferous and saline rock formations in the southern part of the Irkutsk amphitheatre. Intensive economic development of the region, including creation of large industrial enterprises, man-made reservoirs, expansion of irrigation farming, and other activities, have stimulated substantial activation of karst processes, in some places with a more than a 10-fold acceleration.
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EVAPORITE KARST AND RESULTANT GEOHAZARDS IN CHINA1
Lu Yaoru, Zhang Feng'e, Qi Jixiang, Xu Jiaming, and Guo Xiuhong
Institute of Hydrogeology and Engineering Geology, Ministry of Land and Resources, Zhengding, Heibei, China
ABSTRACT: The main kinds of evaporite karst, both sulphate karst and halide karst, are widely distributed in China. Gypsum karst is especially widespread, because China contains the largest gypsum resources in the world. These gypsum deposits range in age from Precambrian to Quaternary, and they were deposited in many environments, including marine, lacustrine, thermal process, metamorphic, and also as secondary deposits. Halide karst is developed in rock salt and salt-water lakes, the latter related to more than 300 salt-water lakes distributed in the Qinghai Plateau of Xizang (Tibet) province.
Gypsum and halite are easily dissolved; therefore, development of evaporite karst is somewhat different when compared with carbonate karst, which has developed many typical features in China. This paper discusses the mechanism and development of evaporite karst in sulphate rocks and in halides, and makes comparisons between evaporite karst and carbonate karst based upon field investigations and new tests in the laboratory.
The geohazards of evaporite karst usually are triggered by natural karst processes, but often they are exaggerated by artificial (human) actions and engineering impacts that cause flesh groundwater or surface water to come in contact with the evaporite rocks. Some examples of evaporite-karst geohazards are described in this paper; they are present in Shandong, Sichuan, and Guizhou Provinces, and in the Qinghai Plateau of China.
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SEQUENCE STRATIGRAPHIC CONTROLS ON THE DEVELOPMENT OF MICROBIAL FABRICS AND GROWTH FORMS - IMPLICATIONS FOR RESERVOIR QUALITY DISTRIBUTION IN THE UPPER JURASSIC (OXFORDIAN) SMACKOVER FORMATION, EASTERN GULF COAST, USA
William C. Parcell
Department of Geology, Wichita State University, Wichita, Kansas 67260; [email protected]
ABSTRACT: This paper presents a model that integrates sequence stratigraphic concepts with a fabric and growth form classification of Smackover microbial buildups to aid in understanding the distribution of reservoir quality in the updip basement ridge play of southwest Alabama. Microbial growth forms and fabrics, early diagenetic processes, and resulting reservoir quality are all ultimately controlled by the rate of relative sea-level change, position of sea level with respect to exposed Paleozoic basement, and position in an inner ramp setting. The microbial classification divides fabrics and growth forms into five "types," which developed in response to changes in water energy, sedimentation rate, and substrate. Layered thrombolite with characteristic mm/cm-scale crypts characterize Type I buildups. Reticulate and "chaotic" thrombolite comprise Type II buildups. In the updip basement ridge play, the Smackover sea did not flood the Paleozoic basement until deposition of the sediments associated with the late transgressive systems tract. Layered and reticulate thrombolite buildups (Types I and II) grew directly on Paleozoic basement and formed in reponse to late transgressive systems tract catch-up conditions when sedimentation rates were low and water energies were moderate to high. Both Type I and II buildups occur on low and high relief basement structures. Type III buildups are characterized by dendroidal thrombolites. On low relief basement structures, dendroidal thrombolite buildups (Type III) typically overlie Type I and II buildups. Type III buildups are absent on high relief structures. Dendritic thrombolites grew in early highstand systems tract keep-up conditions when sedimentation rates were slightly elevated and water energy low. These conditions occurred on the tops of low-relief basement structures associated with early highstand systems tract deposition. Type IV microbialite are composed of isolated stromatolitic crusts that acted as binders to Type V oncoidal packstone/grainstones that grew on soft to firm substrates in high-energy conditions. Abundant in the late highstand systems tract deposits, Type IV (isolated crusts) and V (oncoid) microbialite are found in upper Smackover shoal, lagoon, and tidal flat facies.
Classification of microbial types is significant to hydrocarbon exploration and production in southwest Alabama. Types I, II, and III buildups are the best fabrics for productive reservoirs. Of these, Type III buildups are the highest quality reservoir rocks. Dolomitized reticulate and dendritic fabrics result in well-connected intercrystalline and vuggy porosity. Type IV and V microbialite are poor reservoir rocks because Type IV forms are often isolated, and the moldic porosity associated with Type V oncoids are typically not well connected.
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EOGENETIC KARST FROM THE PERSPECTIVE OF AN EQUIVALENT POROUS MEDIUM
1H.L. Vacher and 2John E. Mylroie
1Department of Geology, University of South Florida, Tampa FL 33620
2Department of Geosciences, Mississippi State University, Mississippi State, MS 39762
ABSTRACT: The porosity of young limestones experiencing meteoric diagenesis in the vicinity of their deposition (eogenetic karst) is mainly a double porosity consisting of touching-vug channels and preferred passageways lacing through a matrix of interparticle porosity. In contrast, the porosity of limestones experiencing subaerial erosion following burial diagenesis and uplift (telogenetic karst) is mainly a double porosity consisting of conduits within a network of fractures. The stark contrast between these two kinds of karst is illustrated by their position on a graph showing the hydraulic characteristics of an equivalent porous medium consisting of straight, cylindrical tubes (n-D space, where n is porosity, D is the diameter of the tubes, and log n is plotted against log D).
Studies of the hydrology of small carbonate islands show that large-scale, horizontal hydraulic conductivity (K) increases by orders of magnitude during the evolution of eogenetic karst. Earlier petrologic studies have shown there is little if any change in the total porosity of the limestone during eogenetic diagenesis. The limestone of eogenetic karst, therefore, tracks horizontally in n-D space. In contrast, the path from initial sedimentary material to telogenetic karst comprises a descent on the graph with reduction of n during burial diagenesis, then a sideways shift with increasing D due to opening of fractures during uplift and exposure, and finally an increase in D and n during development of the conduits along the fractures.
Eogenetic caves are mainly limited to boundaries between geologic units and hydrologic zones: steam caves at the contact between carbonates and underlying impermeable rocks (and collapse-origin caves derived therefrom); vertical caves along platform-margin fractures; epikarst; phreatic pockets (banana holes) along the water table; and flank margin caves that form as mixing chambers at the coastal freshwater-saltwater "interface". In contrast, the caverns of telogenetic karst are part of a system of interconnected conduits that drain an entire region. The eogenetic caves of small carbonate islands are, for the most part, not significantly involved in the drainage of the island.
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SEDIMENTOLOGY OF THE MIOCENE EVAPORITIC SUCCESSION IN THE NORTH OF ÇANKIRI-ÇORUM BASIN, CENTRAL ANATOLIA, TURKEY
1B. Varol, 1H. Araz, 1L. Karadenizli, 1N. Kazanci, 1G. Seyitoglu, and 2S. Sen
1Ankara University, Faculty of Science, Department of Geological Engineering, 06100 Tandogan, Ankara, Turkey, [email protected]
2Laboratoire de Paléontologie, Museum National d' Histoire Naturelle, 8 rue Buffon, 75005 Paris
ABSTRACT: The upper Miocene non-marine sediments of the Çankiri-Çorum basin in central Anatolia, have both evaporitic and non-evaporitic successions. These sediments were deposited in an evaporitic lake which had temporary episodes of palustrine conditions in reponse to seasonal or climatic changes. The successions show different facies such as sulfates, carbonates and siliciclastics. The sulfates comprise primary, reworked and diagenetic gypsum. The primary deposits are predominantly laminated gypsum, bedded gypsum and selenite. The reworked (detrital) gypsum comprises gypsite, gypsarenite, gypsrudite and breccias. The diagenetic type comprises micro- and macrogypsum nodules. The carbonates mainly include clayey limestone, oolitic limestone and dolomite. The siliciclastics comprise red beds and both channel and non-channel, conglomerates and mudstones.
Laminated gypsum, composed of alternating gypsum and dolomite, was a result of environmental schizohalinity. Bedded gypsum was precipitated in the deeper part of the lake during high evaporation periods. Chevron-type selenite crystals formed on saline mud flats during the times of aridity, whereas the discoidal-type seen in the organic-rich mudstones occurred in the gypsiferous marshes during the times of humidity. Reworked (detrital) gypsum dominates the lake margin. These formed during periodic wet episodes that caused reworking of primary gypsum. Gypsum nodules occurred as both early and late diagenetic products. Carbonates and siliciclastics were deposited during the freshening periods of the lake.
Climatic or seasonal changes were the main causes of the depositional styles of the upper Miocene evaporitic and non-evaporitic lacustrine deposits in Çankiri-Çorum basin. Additionally, the transition upward from alluvial to lake environment implies an important change in drainage patterns that likely occurred as a result of marginal fault activity.
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2003 Northeastern Science Foundation