Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [147]-158).

Hicks Dome is a mineralized intrusive center of alkaline ultramafic dikes, plugs and diatreme breccias that produced ~1200 m of structural doming of Paleozoic sedimentary rocks in southeastern Illinois. It is part of an igneous province referred to as the "Wauboukigou Alnöite Province" or "Middle Mississippi Alkaline Province". The 40Ar/39Ar dating of biotite and hornblende from igneous rocks throughout the region has consistently produced crystallization ages of 270 +/- 2 Ma (Early-Middle Permian). Hicks Dome lies near the intersection of two aulacogens, the Reelfoot Rift and the Rough Creek Graben. The igneous rocks in the Hicks Dome area range from dark-green, porphyritic dikes, through dikes with pelletal lapilli, to carbonate cemented breccias with country rock fragments and, locally, phenocrysts or xenocrysts and pelletal lapilli. Magmatic minerals include diopside, pargasite, phlogopite-biotite, titanomagnetite, ilmenite, and apatite, as well as carbonate (ferroan-dolomite - ankerite and calcite) of possible magmatic origin. This mineral assemblage only partly corresponds with other occurrences in the middle Mississippi Valley region igneous province as melilite, garnet, olivine, and perovskite were not identified in the Hicks Dome samples. The Hicks Dome igneous lithotype is defined here as a minette, a type of calc-alkaline lamprophyre. Evidence for this classification includes abundant Al-rich phlogopite-biotite, diopside, and pargasite, and the absence of melilite, garnet, and perovskite. Additionally, plotted Al2O3 vs. TiO2 compositions of biotite-phlogopite form a trend subparallel to that of minettes and alnöites, and Al vs. Ti values for most clinopyroxenes fall in the minette field. Some other igneous occurrences in the region are classified as types of ultramafic lamprophyres. For example, the North Hutson mine (Kentucky) and the Cottage Grove (Illinois) dikes are identified as alnöites and the Wildcat Hills dike (Illinois) is regarded as an aillikite. The Hicks Dome igneous suite contains 23 - 25 wt. % SiO2 and 13 - 21 wt. % CO2, whereas regional igneous rocks contain 33 - 36 wt. % SiO2 and 1 - 2 wt. % CO2. Such high CO2 values and inferred carbonate abundance is likely related to the elevated REE values at Hicks Dome. Finally, Hicks Dome samples show relative depletions in Ti, Nb, Ta, Zr, and Hf on a spider diagram compared to other regional igneous occurrences. These data indicate more variability among provincial igneous rocks than previously realized and perhaps two types of lamprophyres, one a calc-alkaline such as at Hicks Dome, and the other an alkaline ultramafic type. Rock samples from Hicks Dome and the surrounding region that were analyzed far exceed the silica cut-off to be considered a carbonatite (sensu stricto), yet a strong, consistent spatial association of abundant carbonate with igneous rocks throughout the region and similar patterns in LIL (large ion lithophyle), HFS (high field strength) and RE (rare earth) elements with carbonatites worldwide supports that magmatic carbon was part of the lamprophyre system at Hicks Dome. Carbon and oxygen isotope values for carbonate from Hicks Dome and other regional igneous samples do not plot within the field for primary carbonatite or the field for unaltered Mississippian limestone and instead form a broad linear trend between these two reference fields. The observed isotopic trend was possibly due to alteration of primary carbonatite by magmatic-hydrothermal and later low-temperature connate fluids. Parisite and/or synchysite, two REE fluorocarbonates of the bastnäsite group, and xenotime, a Y-(REE) phosphate, were identified in the Hicks Dome samples and occur as fibroradial aggregates in dissolution cavities in fluorite and carbonate and as anhedral crystals infilling microfractures and cleavage planes of phlogopite-biotite and paragasite. These textures clearly indicate the REE minerals are secondary phases most likely resulting from hydrothermal alteration-replacement by magmatic-hydrothermal fluids. A fertile (LREE enriched) lithospheric metasomatized mantle likely sourced the Hicks Dome carbonated alkaline silicate magma that, during emplacement, domed and brecciated the Paleozoic strata, expelled magmatic-hydrothermal fluids, and generated a F-REE mineralizing fluid with abundant carbonate. Igneous activity at Hicks Dome is genetically related to F-REE-base metal mineralization hosted by diatreme breccias, and likely contributed fluorine to the connate brines responsible for the F-base metal mineralization of the surrounding Illinois-Kentucky Fluorspar District (IKFD). Although resource estimates for the Hicks Dome area are beyond the scope of this work, an economic deposit of F, REEs, and/or base metals may be present at Hicks Dome and other igneous occurrences. The igneous lithotype, mineralogy, whole rock geochemistry, and regional geologic context support such a conclusion.

A evolução diagenética de dois reservatórios turbidíticos terciários da porção offshore da Bacia do Espírito Santo, foi influenciada tanto por processos meteóricos como por processos relacionados a domos salinos adjacentes aos reservatórios, que tiveram diferente impacto sobre sua qualidade. A precipitação de pirita framboidal, dolomita microcristalina e siderita ocorreram sob condições eodiagenéticas marinhas. A percolação por água meteórica ocorreu ainda durante a eodiagênese, e promoveu extensiva caulinização (δ18OSMOW=+15.3‰ a +18.2‰; δDSMOW=-51‰ a -66‰) e dissolução de feldspatos, micas e intraclastos lamosos. Durante o progressivo soterramento da sequência (profundidades atuais: 2600-3000m) e consequente compactação, fluidos oriundos dos lutitos circundantes, modificados por reações com a matéria orgânica e carbonatos, deslocaram gradualmente os fluidos salobros marinhos-meteóricos, levando à precipitação de calcita poiquilotópica (valores médios: δ18OVPDB= -6.6‰; δ13CVPDB= -1.2‰). A composição dos fluidos mesodiagenéticos foi progressivamente modificada pela proximidade dos domos de sal, promovendo ubíqua albitização dos feldspatos e precipitação localizada de quartzo, calcita (valores médios: δ18O= -10.2‰; δ13C= -3.9‰) e dolomita em sela (valores médios: δ18O= -10.2‰; δ13C= -4.2‰). A análise de inclusões fluidas nos crescimentos de quartzo indicou que os fluidos precipitantes tinham salinidade predominantemente entre 9 e 13 % de NaCl (em peso) e temperaturas de homogeneização na faixa de 1050 a 1450 C Estes valores são mais altos do que aqueles esperados para o gradiente geotérmico normal da área. A distribuição da albitização dos feldspatos sugere que as fraturas ao longo das margens dos domos de sal atuaram como caminho preferencial para a circulação das salmouras quentes. Os valores de δ13C e δ18O dos cimentos de calcita e dolomita seguem um padrão de covariância, mostrando um declínio desde daqueles representativos da água do mar (~0%), para δ13C =-5.9‰ e δ18O = -10.9‰ para a calcita, e δ13C = -5.4‰ e δ18O = -11.7‰ para a dolomita, o que sugere a progressiva participação da descarboxilação térmica da matéria orgânica dos lutitos com o soterramento. A compactação mecânica foi mais importante do que a cimentação na redução da porosidade, e a dissolução de feldspatos foi o processo mais importante na geração de porosidade nos reservatórios. Apesar da proximidade dos domos de sal, a intensidade dos processos diagenéticos foi moderada, já que não ocorreu autigênese de ilita, e a cimentação de quartzo foi limitada. Estas características podem estar relacionadas com o soterramento relativamente recente destes reservatórios. Este estudo mostra que a predição da diagênese e qualidade de reservatórios relacionados a domos de sal é uma função de múltiplas variáveis, incluindo as dimensões dos domos, o regime térmico regional da bacia, a condutividade térmica e de fluidos, e a composição mineral e propriedades geomecânicas dos reservatórios e litologias associadas. / The diagenetic evolution of two tertiary turbidite reservoirs from the offshore portion of the Espírito Santo Basin, eastern Brazil, was influenced by meteoric and salt dome-related processes, which had different impact on their quality. Marine eogenetic processes included the precipitation of framboidal pyrite, microcrystalline dolomite and siderite. Meteoric water influx during eodiagenesis occurred in response to relative sea-level falls that promoted extensive kaolinization (δ18O=+15.3‰ to +18.2‰; δD= -51‰ to -66‰) and dissolution of framework silicate grains. During progressive burial (present depths – 2600 m – 3000 m), connate marine fluids modified by reactions with organic matter and carbonates presented in the surrounding mudrocks gradually displaced brackish fluids generated by the meteoric influx and led to concretionary cementation by poikilotopic calcite (average δ18O= -6.6‰; δ13C= -1.2‰). Mesogenetic fluids were progressively modified by the proximity of salt domes, which led to ubiquitous feldspar albitization and localized quartz, calcite (average δ18O= -10.2‰; δ13C= -3.9‰) and saddle dolomite precipitation (average δ18O= -10.2‰; δ13C= -4.2‰). Fluid inclusion analysis in quartz overgrowths indicate that the precipitating fluids had salinities predominantly in the range 9-13 wt% NaCl equivalent and temperatures largely in the 105 – 145oC range These values are higher than those expected considering the normal geothermal gradient for the area. The distribution of feldspar albitization suggests that the fracture systems along the salt domes margins acted as preferential pathways for such hot, saline diagenetic fluids. Isotopic values for calcite and dolomite cements follow a co-variance trend of decreasing δ13C and δ18O from close to marine (~0‰) towards negative values (δ13C and δ18O down to -5.9‰ and -10.9‰ for calcite; -5.4‰ and -11.7‰ for dolomite), suggesting increasing contribution from thermal decarboxylation with increasing temperature and depth. Mechanical compaction was more important than cementation in reducing depositional porosity, and the dissolution of framework silicate grains is the most important processes for enhancing reservoir quality. Despite the proximity to the salt domes, the intensity of the influenced diagenetic processes is relatively mild, as illite authigenesis is lacking, and quartz cementation is limited, features that may be related to the recent burial of the reservoirs.

abstract: Silicic volcanoes produce many styles of activity over a range of timescales. Eruptions vary from slow effusion of viscous lava over many years to violent explosions lasting several hours. Hazards from these eruptions can be far-reaching and persistent, and are compounded by the dense populations often surrounding active volcanoes. I apply and develop satellite and ground-based remote sensing techniques to document eruptions at Merapi and Sinabung Volcanoes in Indonesia. I use numerical models of volcanic activity in combination with my observational data to describe the processes driving different eruption styles, including lava dome growth and collapse, lava flow emplacement, and transitions between effusive and explosive activity. Both effusive and explosive eruptions have occurred recently at Merapi volcano. I use satellite thermal images to identify variations during the 2006 effusive eruption and a numerical model of magma ascent to explain the mechanisms that controlled those variations. I show that a nearby tectonic earthquake may have triggered the peak phase of the eruption by increasing the overpressure and bubble content of the magma and that the frequency of pyroclastic flows is correlated with eruption rate. In 2010, Merapi erupted explosively but also shifted between rapid dome-building and explosive phases. I explain these variations by the heterogeneous addition of CO2 to the melt from bedrock under conditions favorable to transitions between effusive and explosive styles. At Sinabung, I use photogrammetry and satellite images to describe the emplacement of a viscous lava flow. I calculate the flow volume (0.1 km3) and average effusion rate (4.4 m3 s-1) and identify active regions of collapse and advance. Advance rate was controlled by the effusion rate and the flow’s yield strength. Pyroclastic flow activity was initially correlated to the decreasing flow advance rate, but was later affected by the underlying topography as the flow inflated and collapsed near the vent, leading to renewed pyroclastic flow activity. This work describes previously poorly understood mechanisms of silicic lava emplacement, including multiple causes of pyroclastic flows, and improves the understanding, monitoring capability, and hazard assessment of silicic volcanic eruptions. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2016

A evolução diagenética de dois reservatórios turbidíticos terciários da porção offshore da Bacia do Espírito Santo, foi influenciada tanto por processos meteóricos como por processos relacionados a domos salinos adjacentes aos reservatórios, que tiveram diferente impacto sobre sua qualidade. A precipitação de pirita framboidal, dolomita microcristalina e siderita ocorreram sob condições eodiagenéticas marinhas. A percolação por água meteórica ocorreu ainda durante a eodiagênese, e promoveu extensiva caulinização (δ18OSMOW=+15.3‰ a +18.2‰; δDSMOW=-51‰ a -66‰) e dissolução de feldspatos, micas e intraclastos lamosos. Durante o progressivo soterramento da sequência (profundidades atuais: 2600-3000m) e consequente compactação, fluidos oriundos dos lutitos circundantes, modificados por reações com a matéria orgânica e carbonatos, deslocaram gradualmente os fluidos salobros marinhos-meteóricos, levando à precipitação de calcita poiquilotópica (valores médios: δ18OVPDB= -6.6‰; δ13CVPDB= -1.2‰). A composição dos fluidos mesodiagenéticos foi progressivamente modificada pela proximidade dos domos de sal, promovendo ubíqua albitização dos feldspatos e precipitação localizada de quartzo, calcita (valores médios: δ18O= -10.2‰; δ13C= -3.9‰) e dolomita em sela (valores médios: δ18O= -10.2‰; δ13C= -4.2‰). A análise de inclusões fluidas nos crescimentos de quartzo indicou que os fluidos precipitantes tinham salinidade predominantemente entre 9 e 13 % de NaCl (em peso) e temperaturas de homogeneização na faixa de 1050 a 1450 C Estes valores são mais altos do que aqueles esperados para o gradiente geotérmico normal da área. A distribuição da albitização dos feldspatos sugere que as fraturas ao longo das margens dos domos de sal atuaram como caminho preferencial para a circulação das salmouras quentes. Os valores de δ13C e δ18O dos cimentos de calcita e dolomita seguem um padrão de covariância, mostrando um declínio desde daqueles representativos da água do mar (~0%), para δ13C =-5.9‰ e δ18O = -10.9‰ para a calcita, e δ13C = -5.4‰ e δ18O = -11.7‰ para a dolomita, o que sugere a progressiva participação da descarboxilação térmica da matéria orgânica dos lutitos com o soterramento. A compactação mecânica foi mais importante do que a cimentação na redução da porosidade, e a dissolução de feldspatos foi o processo mais importante na geração de porosidade nos reservatórios. Apesar da proximidade dos domos de sal, a intensidade dos processos diagenéticos foi moderada, já que não ocorreu autigênese de ilita, e a cimentação de quartzo foi limitada. Estas características podem estar relacionadas com o soterramento relativamente recente destes reservatórios. Este estudo mostra que a predição da diagênese e qualidade de reservatórios relacionados a domos de sal é uma função de múltiplas variáveis, incluindo as dimensões dos domos, o regime térmico regional da bacia, a condutividade térmica e de fluidos, e a composição mineral e propriedades geomecânicas dos reservatórios e litologias associadas. / The diagenetic evolution of two tertiary turbidite reservoirs from the offshore portion of the Espírito Santo Basin, eastern Brazil, was influenced by meteoric and salt dome-related processes, which had different impact on their quality. Marine eogenetic processes included the precipitation of framboidal pyrite, microcrystalline dolomite and siderite. Meteoric water influx during eodiagenesis occurred in response to relative sea-level falls that promoted extensive kaolinization (δ18O=+15.3‰ to +18.2‰; δD= -51‰ to -66‰) and dissolution of framework silicate grains. During progressive burial (present depths – 2600 m – 3000 m), connate marine fluids modified by reactions with organic matter and carbonates presented in the surrounding mudrocks gradually displaced brackish fluids generated by the meteoric influx and led to concretionary cementation by poikilotopic calcite (average δ18O= -6.6‰; δ13C= -1.2‰). Mesogenetic fluids were progressively modified by the proximity of salt domes, which led to ubiquitous feldspar albitization and localized quartz, calcite (average δ18O= -10.2‰; δ13C= -3.9‰) and saddle dolomite precipitation (average δ18O= -10.2‰; δ13C= -4.2‰). Fluid inclusion analysis in quartz overgrowths indicate that the precipitating fluids had salinities predominantly in the range 9-13 wt% NaCl equivalent and temperatures largely in the 105 – 145oC range These values are higher than those expected considering the normal geothermal gradient for the area. The distribution of feldspar albitization suggests that the fracture systems along the salt domes margins acted as preferential pathways for such hot, saline diagenetic fluids. Isotopic values for calcite and dolomite cements follow a co-variance trend of decreasing δ13C and δ18O from close to marine (~0‰) towards negative values (δ13C and δ18O down to -5.9‰ and -10.9‰ for calcite; -5.4‰ and -11.7‰ for dolomite), suggesting increasing contribution from thermal decarboxylation with increasing temperature and depth. Mechanical compaction was more important than cementation in reducing depositional porosity, and the dissolution of framework silicate grains is the most important processes for enhancing reservoir quality. Despite the proximity to the salt domes, the intensity of the influenced diagenetic processes is relatively mild, as illite authigenesis is lacking, and quartz cementation is limited, features that may be related to the recent burial of the reservoirs.

abstract: A cerebral aneurysm is a bulging of a blood vessel in the brain. Aneurysmal rupture affects 25,000 people each year and is associated with a 45% mortality rate. Therefore, it is critically important to treat cerebral aneurysms effectively before they rupture. Endovascular coiling is the most effective treatment for cerebral aneurysms. During coiling process, series of metallic coils are deployed into the aneurysmal sack with the intent of reaching a sufficient packing density (PD). Coils packing can facilitate thrombus formation and help seal off the aneurysm from circulation over time. While coiling is effective, high rates of treatment failure have been associated with basilar tip aneurysms (BTAs). Treatment failure may be related to geometrical features of the aneurysm. The purpose of this study was to investigate the influence of dome size, parent vessel (PV) angle, and PD on post-treatment aneurysmal hemodynamics using both computational fluid dynamics (CFD) and particle image velocimetry (PIV). Flows in four idealized BTA models with a combination of dome sizes and two different PV angles were simulated using CFD and then validated against PIV data. Percent reductions in post-treatment aneurysmal velocity and cross-neck (CN) flow as well as percent coverage of low wall shear stress (WSS) area were analyzed. In all models, aneurysmal velocity and CN flow decreased after coiling, while low WSS area increased. However, with increasing PD, further reductions were observed in aneurysmal velocity and CN flow, but minimal changes were observed in low WSS area. Overall, coil PD had the greatest impact while dome size has greater impact than PV angle on aneurysmal hemodynamics. These findings lead to a conclusion that combinations of treatment goals and geometric factor may play key roles in coil embolization treatment outcomes, and support that different treatment timing may be a critical factor in treatment optimization. / Dissertation/Thesis / M.S. Bioengineering 2013

Este trabalho tem como objetivo discutir a evolução tectônica meso-cenozóica do Domo de Lages, SC, envolvendo análise das estruturas rúpteis que afetam as rochas da região, análise morfométrica e da rede de drenagem e aspectos geomorfológicos relevantes. O Domo de Lages, localizado na borda leste da Bacia do Paraná, na porção sul do estado de Santa Catarina, é caracterizado pela ocorrência de uma grande variedade de rochas alcalinas de idade neo-cretácea. Estas rochas afloram na forma de sills e diques e são intrusivas no pacote sedimentar da Bacia do Paraná, causando-lhe um soerguimento da ordem de centenas a milhares de metros. As rochas alcalinas foram afetadas por estruturas rúpteis, particularmente falhas transcorrentes e normais, denotando a presença de uma tectônica ativa durante o cenozóico. Para o entendimento do quadro evolutivo do domo, além da análise estrutural, foram elaborados diversos mapas morfométricos (hipsométrico, declividades, orientação de vertentes, superfícies de base, rugosidade, gradiente hidráulico e densidade de lineamentos e drenagens) derivados diretamente do Modelo Digital de Elevação, que por sua vez foi obtido pelo tratamento de dados SRTM (Shuttle Radar Topographic Mission) da Agência Espacial Americana (NASA). O trabalho foi complementado com a análise da rede de drenagem e de lineamentos extraídos de imagens, juntamente com a elaboração de perfis topográficos. Os resultados mostram tratar-se de uma estrutura dômica alongada com eixo maior orientado na direção NW-SE, marcada pelo alinhamento de intrusões alcalinas e basculamento dos acamamentos das rochas sedimentares que apresentam mergulho radial para fora da estrutura. A análise do relevo revelou a existência de uma superfície de aplainamento, hoje preservada na cota de 1200 m, que teria sido afetada por falhas normais de direções NW-SE e NE-SW. O modelo tectônico evolutivo elaborado para a região contempla a seguinte seqüência de eventos: atuação de esforços compressivos NE-SW no final do cretáceo, gerando falhas normais NE-SW, que afetam as rochas básicas da Formação Serra Geral e condicionam a colocação de diques alcalinos e a estruturação do domo; geração de falhas transcorrentes destrais que afetam todas as rochas da região, incluindo as rochas alcalinas, com binário orientado na direção NNE-SSW; configuração de uma superfície de aplainamento preservada na cota de 1200m, que perdurou, provavelmente, até o mioceno; distensão NE-SW e geração de falhas normais NW-SE que abatem e basculam a superfície aplainada e reorganizam a rede de drenagens; instalação de um provável evento distensivo NW-SE, responsável pela formação de falhas normais NE-SW, marcadas principalmente nos mapas morfométricos. / This study was focused on the meso-cenozoic tectonic evolution of the Domo de Lages region (south Santa Catarina State, Southern Brazil), through the analysis of brittle structures affecting sedimentary and igneous rocks, morphometric parameters, drainage network and main geomorphological features. Located in the border of the Paraná sedimentary basin, the Domo de Lages is characterized by a great variety of Late Cretacic alkaline rocks, which crops out as sills and dikes cutting the Paleozoic sedimentary rocks, and are associated with an uplift of hundreds to thousands of meters. These alkaline rocks are affected by brittle structures, mainly transcurrent and normal faults, indicative of Cenozoic active tectonics. In addition to the structural analysis, several morphometric maps were developed, as an aid to enlighten the evolutionary history of the region. Maps of hypsometry, slope, aspect, isobase surfaces, surface roughness, hydraulic gradient, lineament density and drainage density were derived from SRTM (Shuttle Radar Topographic Mission) Digital Elevation Models provided by NASA, and were complemented by topographic profiles, analysis of drainage network and lineament orientation. Results show that the dome has a elongated shape with major axis oriented NW-SE, defined by alignment of intrusive bodies and tilting of sedimentary rocks bedding planes, dipping radially outwards the center of the structure. Topographic analysis revealed the existence of a planation surface, preserved at 1200m a.s.l., wich would have been affected by NW-SE and NE-SW normal faults. A tectonic evolutionary model for the region was elaborated, according the following sequence of events: in the end of Cretaceous, a compressive NE stress generates NE-SW normal faults, which affect the basic rocks of Serra Geral Formation and controls the emplacement of alkaline dikes and the uplift of the domic structure; formation of transcurrent dextral faults affecting all rocks of the area, including the alkalines, with NNE-SSW oriented binary; development of a planation surface preserved at 1200m a.s.l. which remained probably until the Miocene; NE-SW extension, creating NW-SE normal faults that lowered and tilted the levelled surface and affected the drainage network; a last extensive NW-SE event probably happened, responsible for NE-SW normal faults seen mainly in the morphometric maps.

Prevalence of osteoarthritis (OA) is less common in the ankle compared to other joints; however, deformation brought on by degeneration causes pain, loss of function, and overall decreased quality of life. Current surgical interventions for end-stage ankle OA are not as reliable as surgical treatments for other joints. Ankle arthroplasty currently has high failure rates, and there are lack of substantial data from long-term outcome studies. By understanding the morphometric changes that occur during the different stages of OA, we are able to identify early signs of the disease with the intention to apply treatment earlier in order to preclude the need for end-stage surgical intervention. The goals of this study are to assess morphometric parameters of the talus as it relates to the progression of OA and to evaluate the effect of gender and anatomical side. A retrospective study was performed where data from sixty-eight CT scans were obtained from two study groups, one with OA and one without. The subjects were segmented, standardized, and normalized in order to study several 3D parameters of the talus, including height, radius of curvature, and volume. Results showed that talar morphometry is influenced by gender and that geometric changes are a function of OA progression. The lateral radii of subjects with OA was significantly larger than those of normal ankles (p<0.0001), and there is evidence of inherent changes between KL grades (p=0.0003). Identifying morphometric changes of the talus at each stage of OA can inherently contribute to better understanding the degenerative process. Assessing specific characteristics at earlier stages of the diseases may help clinicians to diagnose more accurately and to better provide treatment.

No description available.

Habitat loss and fragmentation are some of the causes of biodiversity decline. Naturally fragmented landscapes serve as analogues to anthropogenically fragmented landscapes. Recent studies have shown that the matrix between patches has an important role in the dynamics of patch-dwelling species. I studied phenology and habitat utilization of Hyla cinerea and Hyla squirella, the two most common yet understudied frogs, in two patchy landscapes of the Big Cypress National Preserve. Frogs were sampled in five domes and in their adjacent matrix, monthly, between 2006 and 2008. Using nighttime visual encounter surveys, specimens encountered were identified to species, and perch type, perch height and capture location were recorded. Analysis showed differences in abundance and habitat use patterns between patches and matrices for the two species across the two landscapes. These differences indicate that the matrix is important in shaping patterns of abundance and habitat use in fragmented landscapes.