Variations in trace element abundances with depth in soils and sediments may be due to natural processes or reflect anthropogenic influences. The depth related variations of five major elements (Fe, Si, Al, Ca and Mg), seventeen trace elements (Mn, Cr, Ti, P, Ni, Ba, Sc, Sr, Sb, Zn, Pb, Cd, Co, V, Be, Cu and Y) and volatile loss patterns were examined for sediment cores from five sites in South Florida (Lake Okeechobee, SFWMD Water Conservation area 3B, F.I.U., the Everglades and Chekika State Recreation Area). Principal component analysis of the chemical data combined with microscopic examination of the soils reveal that depth-related variations can be explained by varying proportions of three natural soil constituents and one anthropogenic component. The results can be used as a geochemical baseline for human influence on South Florida soils.

Calbuco Volcano, in Southern Chile, has eruptive products of predominantly andesitic hornblende-bearing lava. A purpose of this work is to understand magmatic processes and how Calbuco magma chemistry is related to the explosive volcanic character. Calbuco lava has a mineral assemblage of plagioclase, hornblende, orthopyroxene, clinopyroxene, olivine, and magnetite and entrained gabbroic xenoliths with the same mineral assemblage. The presence of hornblende is evidence for dissolved water in the magma. Detailed petrographic/textural analysis has been done using petrographic microscopy and back-scattered electron imaging (BSE); geochemical analysis by electron microprobe (EPMA). Major findings include 1) that hornblende and hornblende-bearing gabbroic cumulates crystallize from Calbuco magma, 2) that plagioclase grains are compositionally zoned, recording evidence of temperature, chemical, and water content fluctuations in the magma, and 3) that hornblende is unstable under upper magma chamber conditions at Calbuco, and is breaking down into plagioclase, olivine, orthopyroxene, clinopyroxene, and magnetite in the magma.

Subduction zone magmatism is an important and extensively studied topic in igneous geochemistry. Recent studies focus on from where arc magmas are generated, how subduction components (fluids or melts) are fluxed into the source of the magmas, and whether or how the subduction components affect partial melting processes beneath volcanic arcs at convergent boundaries. At 39.5°S in the Central Southern Volcanic Zone of the Andes, Volcano Villarrica is surrounded by a suite of Small Eruptive Centers (SEC). The SECs are located mostly to the east and northeast of the stratovolcano and aligned along the Liquine - Ofqui Fault Zone, the major fracture system in this area. Former studies observed the geochemical patterns of the SECs differ distinctively from those of V.Villarrica and suggested there may be a relationship between the compositions of the volcanic units and their edifice sizes. This work is a comprehensive geochemical study on the SECs near V.Villarrica, using a variety of geochemical tracers and tools including major, trace and REE elements, Li - Be - B elements, Sr - Nd - Pb isotopes and short - lived isotopes such as U - series and 10Be. In this work, systematic differences between the elemental and isotopic compositions of the SECs and those of V.Villarrica are revealed and more importantly, modeled in terms of magmatic processes occurring at continental arc margins. Detailed modeling calculations in this work reconstruct chemical compositions of the primary magmas, source compositions, compositions and percentages of different subduction endmembers mixed into the source, degrees of partial melting and different time scales of the SECs and V.Villarrica, respectively. Geochemical characteristics and possible origins of the two special SECs - andesitic Llizan, with crustal signatures, and Rucapillan, to the northwest toward the trench, are also discussed in this work.

Hydrogeologic variables controlling groundwater exchange with inflow and flow-through lakes were simulated using a three-dimensional numerical model (MODFLOW) to investigate and quantify spatial patterns of lake bed seepage and hydraulic head distributions in the porous medium surrounding the lakes. Also, the total annual inflow and outflow were calculated as a percentage of lake volume for flow-through lake simulations. The general exponential decline of seepage rates with distance offshore was best demonstrated at lower anisotropy ratio (i.e., Kh/Kv = 1, 10), with increasing deviation from the exponential pattern as anisotropy was increased to 100 and 1000. 2-D vertical section models constructed for comparison with 3-D models showed that groundwater heads and seepages were higher in 3-D simulations. Addition of low conductivity lake sediments decreased seepage rates nearshore and increased seepage rates offshore in inflow lakes, and increased the area of groundwater inseepage on the beds of flow-through lakes. Introduction of heterogeneity into the medium decreased the water table and seepage ratesnearshore, and increased seepage rates offshore in inflow lakes. A laterally restricted aquifer located at the downgradient side of the flow-through lake increased the area of outseepage. Recharge rate, lake depth and lake bed slope had relatively little effect on the spatial patterns of seepage rates and groundwater exchange with lakes.

Two Barremian-Aptian sequences studied in Durango and Nuevo Leon States, northeastern Mexico include three lithic units which have been described as the Cupido Formation of Barremian-early Early Aptian age, its lateral equivalent, the Lower Tamaulipas Formation, and the La Pena Formation extending through the early Albian. The present work improves the existing ammonite Aptian biozonation by considering constraints associated with a discontinuous spatial and temporal record of the different taxa within the La Pena Formation. Four ammonite biozones are established: 1) The Dufrenoyia justinae Zone for the late Early Aptian, 2) The Burckhardtites nazasensis/Rhytidoplites robertsi Zone for the middle Aptian, 3) The Cheloniceras inconstans Zone for the early Late Aptian, and 4) The Hypacanthoplites cf. leanzae Zone for the late late Aptian. Also, a detailed sedimentological analysis of the sections shed further light on the possible causes that controlled intermittent occurrences of the ammonites in relation to the prevailing paleoceanographic and paleoecologic conditions in northeastern Mexico during the late Barremian-Aptian. Microfacies analyses show that the upper part of the Cupido facies are represented by biocalcirudite with rudists, biocalcarenites with oolites and algae, and rich benthonic foraminifera assemblages with ostracods. These facies are related to paleoceanographic conditions of sedimentation within a shallow-marine carbonate platform. Its lateral equivalent, deep-water facies extended to the southeast and it is represented by the Lower Tamaulipas Formation, which includes planktonic foraminifera, ostracods, and mollusk and echinoid fragments. The beginning of deposition of the La Pena Formation in the late Early Aptian is characterized by an increase in terrigenous materials and significant decrease in the abundance of benthic fauna. The La Pena Formation is recognized by an alternation of marls and shale limestones containing ammonites, planktonic foraminifera, ostracods, and radiolaria toward the top. Accumulation of the La Pena continued throughout the end of the Aptian and records changes in conditions of sedimentation and productivity in the water column, which abruptly terminated the carbonate deposition in the Cupido Platform. Results of carbon/carbonate content analyses show that changes from the Cupido to the La Pena facies are also characterized by an increase of organic carbon, which indicate the onset of enhanced dysoxic/anoxic conditions in the lower water column.

<p> Seismic features on a seismic horizon at or near the Cretaceous-Paleogene boundary in northern Louisiana seen by Egedahl (2012), and then studied in greater depth by Strong (2013), resemble large subaqueous dunes or &ldquo;mega-ripples.&rdquo; Both Egedahl (2012) and Strong (2013) hypothesize that these features represent subaqueous dunes emplaced by tsunami waves caused by the Chicxulub Impact, the large bolide impact on the Yucat&aacute;n Peninsula, that is widely agreed to be one of the contributing factors to the demise of the dinosaurs. Three hundred and eighteen well logs in northern Louisiana were analyzed to determine whether possible subaqueous dunes are evidenced at the Cretaceous-Paleogene boundary in this data set. These same well logs were used to develop a contour map of the top of Cretaceous and to determine the topography of the top of the Cretaceous in northern Louisiana at the time of the Chicxulub Impact. Further, the log facies of these logs were interpreted to deduce paleo-shoreline for this topography at the time of the Cretaceous-Paleogene boundary.</p><p>

The $\sim$1.9 Ga Gunflint Formation is a Lake Superior type iron-formation, located in the Thunder Bay district of northwestern Ontario, that was deposited on a shallow shelf analogous to modern carbonate environments. Carbonate minerals in the iron-rich lithofacies of the Gunflint Formation include siderite, ankerite, and calcite. Petrographic evidence indicates that siderite precipitation initiated either within the water column or at the sediment/water interface and continued during very early diagenesis. Ankerite and calcite formed during early to late diagenesis as pore-filling cements and as replacements of other minerals. The iron-poor limestone facies contains very early diagenetic dolomite and early to late diagenetic calcite. $\delta\sp $C values of carbonate minerals from unmetamorphosed rocks range between 0 and $-6\perthous$ (PDB). The values near 0$\perthous,$ which are considered to be representative of the basin water composition, indicate that the primary source of carbon was marine bicarbonate. The lighter values indicate that a minor component of oxidized organic carbon was added during early diagenesis. The heaviest $\delta\sp $O values for unmetamorphosed carbonate minerals range between $-$5 and $-7\perthous$ (PDB), which is the same range of values observed for many early Proterozoic marine carbonates. $\delta\sp $O values of carbonate minerals are the result of isotopic exchange with pore waters, originally of marine composition, at increasing temperatures and/or are the result of isotopic exchange with $\sp $O-depleted meteoric water during early diagenesis. Disseminated fine-grained, very early diagenetic pyrite is widespread throughout the formation, usually in amounts less than about 2%. However, pyrite is locally observed as laminae or thin layers, suggesting that some pyrite may have formed at or above the sediment/water interface. Low S/C ratios indicate that dissolved sulphate was the limiting factor in pyrite formation. $\delta\sp{34}$S values between +5 and +12$\perthous$ (CDT) imply that sulfide formed by bacterial sulphate reduction under closed system conditions. In the lower part of the Gunflint Formation coarse-grained pyrite and pyrite concretions are associated with syndepositional faults. High S/C ratios and highly variable $\delta\sp{34}$S values ($-$33 to +35$\perthous)$ suggest an external source of sulphate was introduced by fluids moving upward along these faults. The Gunflint basin is best characterized by a stratified water column with high concentrations of dissolved ferrous iron below the redox boundary. Volcanic activity or rifting within this basin contributed a high flux of reducing hydrothermal solutions to the seawater. Hydrothermal activity was probably the dominant source of iron, although reduction of detrital ferric iron may have contributed significant amounts of dissolved iron. During periods of increased tectonic activity, the expansion of the redox boundary to shallower water allowed the transport of iron to the shallow shelf. Ferric iron-bearing minerals would have been precipitated on the shelf by oxidation in surface waters whereas ferrous iron-bearing minerals would have been precipitated under more reducing conditions either in deeper water or in sheltered environments. The transition to the iron-poor limestone member resulted from a lowering of the redox boundary. (Abstract shortened by UMI.)

The Lake Shore Au deposit lies in the Kirkland Lake Au camp, the second largest Archean camp in North America. The deposit is hosted in an alkaline to sub-alkaline intrusive complex composed of augite syenite, syenite, feldspar porphyry and quartz-feldspar porphyry. Feldspar and quartz-feldspar porphyry are the latest of the intrusive phases within the Lake Shore property and host over two-thirds of the Au in the camp. Detailed petrography and geochemistry of the feldspar porphyry indicate that it is predominantly a quartz-monzodiorite. The primary mineralogy of this unit consists of plagioclase, orthoclase, biotite, and hornblende, with accessory magnetite, apatite, titanite, monazite, and zircon. Miarolitic cavities within this unit suggest a relatively shallow level of emplacement as well as an H$\sb2$O-rich nature for the magma. Four successive alteration facies are recognized within the feldspar porphyry. The concentric nature of the later three alteration facies as zones about the auriferous veins may be the result of several overprinting, chemically distinct hydrothermal events, each of which penetrated the wall rocks to subsequent decreasing depths. A second possibility is that they are the result of a fluid which evolved as it penetrated the wall rocks. (Abstract shortened by UMI.)

The middle to late Emsian clastic succession of the western Chaleur Bay region comprises the newly defined Pointe la Nim Formation and the overlying Campbellton Formation. The type and orientations of the fluvial systems present in the succession lends insight into the larger scale basin configurations and the nature and timing of major allocyclic events. The succession documents a transition from synvolcanic to syntectonic fluvial sedimentation related to a transition from subduction related island arc volcanism to uplift and dissection of the volcanic arc during the early stages of the Acadian Orogeny. The middle Emsian Pointe la Nim Formation is composed of interbedded extrusive volcanics, pyroclastics, and a wide range of fluvial deposits which exhibit a southwestwards to northeastwards proximal to distal trend. The mid to late Emsian Campbellton Formation overlies the Pointe la Nim Formation with local discordance, and can be subdivided into four distinct members: the lacustrine Atholville Member and the fluvial Pointe a la Garde, Pointe a Bourdeau, and Restigouche Members. (Abstract shortened by UMI.)

Several metavolcanic-metasedimentary belts containing komatiites have been found in the Baker Lake region, N.W.T. In particular, a sequence of flows of komatiitic composition within the Woodburn Lake Group (WLG) show well preserved flow tops, polyhedral jointing, and spinifex textures, confirming their volcanic origin. The Woodburn Lake Group consists of a lower 2.8-3.0(?)Ga predominantly volcanic greenstone sequence and an upper platformal quartzite sequence. The lowermost rocks of the volcanic sequence comprise an essentially bimodal assemblage of komatiites-komatiitic basalts and dacites-rhyolites; intermediate rocks are rare. The uppermost rocks reflect a change in volcanic activity from komatiitic-tholeiitic to calc-alkaline in nature. This change is accompanied by an increase in sedimentation. The supracrustal succession is presently preserved as narrow linear belts within Late Archean (2.6 Ga) granitic to granodiorite plutons. Although there is no recognized pre-greenstone basement, the upper quartzite sequence suggests the presence of older sialic crust nearby. The komatiites and komatiitic basalts (including high-Mg tholeiites) have been altered by greenschist grade regional metamorphism with complete replacement of primary mineralogy, but with excellent preservation of primary textures. The typical mineralogy of the komatiites is tremolite - antigorite - chlorite - Cr-magnetite and of the komatiitic basalts is amphibole - chlorite - magnetite - plagioclase - epidote - quartz. The grade of metamorphism increases toward the margins of the WLG belts to amphibolite grade as a result of contact metamorphism by younger granitoids. Olivine-spinel geothermometry gives a temperature of 625$\sp\circ$C for contact metamorphism of the komatiites. Chemical variation diagrams of the komatiitic suites reflect variable degrees of element remobilization during alteration. Al, Ti, V, Cr, Ni, and Sc were immobile, whereas Na, K, Ca, Rb, Sr, and LREE exhibit variable mobility. Most ratios of incompatible elements (i.e. Zr, and LREE) show moderate to strong depletion of these elements in the komatiites and strong enrichment in the komatiitic basalts. The WLG komatiites are typical of the aluminum-undepleted type that characterizes Late Archean terrains. The WLG komatiitic basalts are geochemically similar to those from Kambalda (Australia), the Abitibi Greenstone Belt, and modern-day volcanic arcs. Fractional crystallization explains the compositional variations within individual volcanic units, but does not explain adequately the differences between komatiites and komatiitic basalts. The Kambalda komatiitic basalts have been interpreted as resulting from crustal contamination and fractional crystallization of komatiitic magmas within an intra-continental setting. Quantitative modelling suggests derivation of the WLG komatiitic basalts by 20-40% crustal contamination of komatiitic magmas. Alternatively, the geochemical similarity to modern-day arc volcanics suggests an arc-related origin for the komatiitic basalts. REE patterns and inter-element ratios indicate that the mantle source region of the WLG komatiites underwent an early melting event, leaving it depleted in Zr and LREE. 30 to 40% partial melting of this source (assumed to be garnet lherzolite in composition) generated the komatiitic liquids. The WLG is compositionally and lithologically similar to the Prince Albert Group and hence probably correlative. Origin of the komatiitic suite in a continental margin arc-type environment is the favoured interpretation but an ensialic rifting model cannot be ruled out.