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Late Tertiary post-orogenic alkaline basalts erupted in the extensional Pannonian Basin following Eocene-Miocene subduction and its related calc-alkaline volcanism. The alkaline volcanic centres, dated between 11-7 and 1-4 Ma, are... more
Late Tertiary post-orogenic alkaline basalts erupted in the extensional Pannonian Basin following Eocene-Miocene subduction and its related calc-alkaline volcanism. The alkaline volcanic centres, dated between 11-7 and 1-4 Ma, are concentrated in several regions of the Pannonian Basin. Some are near the western (Graz Basin, Burgenland), northern (Nograd), and eastern (Transylvania) margins of the basin, but the majority are concentrated near the Central Range (Balaton area and Little Hungarian Plain). Fresh samples from 31 volcanic centres of the extension-related lavas range from slightly hy-normative transitional basalts through alkali basalts and basanites to olivine nephelinites. No highly evolved compositions have been encountered. The presence of peridotite xenoliths, mantle xenocrysts, and high-pressure megacrysts, even in the slightly more evolved rocks, indicates that differentiation took place within the upper mantle. Rare earth elements (REE) and 87Sr/*6Sr, 143Nd/14*Nd, c...
A bibliography of published articles and reports on mineral-separation techniques, processes, and applications is presented along with an author and subject index. This information is intended for use in the mineral-separation facility of... more
A bibliography of published articles and reports on mineral-separation techniques, processes, and applications is presented along with an author and subject index. This information is intended for use in the mineral-separation facility of the Lunar Receiving Laboratory at the NASA Manned Spacecraft Center and as an aid and reference to persons involved or interested in mineral separation.
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... (1979) and Thirlwall and Graham (1984). Overall, Gre nada lavas have lower 143Nd 144Nd and substantially higher 87Sr Srsr than Atlantic MORB, forming a data array on Fig. 4 offset to higher 87Sr S6Sr than ocean islands. ...
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Chemical and O-, Sr-, Nd-, and Pb-isotope relations for the British Caledonian granitoids exhibit systematic variations that are attributed to derivation from both mantle and crustal sources. The ‘older’ (more than ca . 470 Ma) pre- and... more
Chemical and O-, Sr-, Nd-, and Pb-isotope relations for the British Caledonian granitoids exhibit systematic variations that are attributed to derivation from both mantle and crustal sources. The ‘older’ (more than ca . 470 Ma) pre- and syn-tectonic granites were the product of local anatectic melting of Late Proterozoic metasedimentary upper crust (8 18 O æ 8 to 14% 0 , 87 S r/ 86 Sr > 0.710, 206 Pb / 204 Pb « 18.1-19.2) during the peak thermal conditions of the Grampian Orogeny. The ‘younger’ (less than ca . 440 Ma) post-tectonic granitoids have a complex origin which, in individual cases, involved at least four different source regions: (i) the upper mantle or subducted oceanic crust (8 18 O « 5.7 to 7.0%o, 87 Sr/ 86 Sr « 0.7035-0.7040, 206 Pb/ 204 Pb = 17.9 to 18.1) and (ii) Lower Palaeozoic geosynclinal sedimentary upper crust (8 18 O « 11 to 14% 0 , 87 Sr/ 86 Sr « 705-0.711, 206 Pb/ 204 Pb « 18.4) within the paratectonic Caledonides in the Scottish Midland Valley and Southe...
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Geology and Geochemistry
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A combination of hydrogen and oxygen isotope analyses and fluid inclusion studies has defined the composition of fluids involved in the metamorphism of Lower Palaeozoic rocks in the English Lake District. Three fluid fields have been... more
A combination of hydrogen and oxygen isotope analyses and fluid inclusion studies has defined the composition of fluids involved in the metamorphism of Lower Palaeozoic rocks in the English Lake District. Three fluid fields have been defined from secondary phases: 1, syn-burial metamorphic D-enriched fluids from epidote and chlorite at a temperature between 250 and 350°C; D-depleted fluid measured from groundmass and quartz inclusions; 3, a mixed magmatic-meteoric fluid with an intermediate H-isotopic composition estimated from W/R granite data and calculated from illite.
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ABSTRACT. A combination of hydrogen and oxygen isotope analyses and fluid inclusion studies has defined the composition of fluids involved in the metamorphism of Lower Palaeozoic rocks in the English Lake District. Three fluid fields have... more
ABSTRACT. A combination of hydrogen and oxygen isotope analyses and fluid inclusion studies has defined the composition of fluids involved in the metamorphism of Lower Palaeozoic rocks in the English Lake District. Three fluid fields have been defined from secondary phases: 1, syn-burial metamorphic D-enriched fluids from epidote and chlorite at a temperature b tween 250 and 350 ~ 2, D-depleted fluid measured from groundmass and quartz inclusions; 3, a mixed magmatic-meteoric fluid with an intermediate H-isotopic omposition esti-mated from W/R granite data and calculated from illite.
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Oxygen isotope data are presented for 37 samples of subduction-related lavas from the Aeolian Islands, southern Italy, that were characterised for radiogenic isotopes (Sr, Nd, Pb) and major- and trace-element abundances in previous... more
Oxygen isotope data are presented for 37 samples of subduction-related lavas from the Aeolian Islands, southern Italy, that were characterised for radiogenic isotopes (Sr, Nd, Pb) and major- and trace-element abundances in previous studies. The samples, which were all erupted within the past 500,000 years, span the full compositional range of Aeolian magmatism from the calc-alkaline basalt-dacite sequence of Salina to the shoshonites of Stromboli and the potassic leucite-bearing basalt to rhyolite series of Vulcano, Whole-rock δ18O values range from +6.3‰ to +8.5‰, but in some cases (14 samples) 18O enrichment by post-crystallization hydration and low-temperature alteration is suspected, and an empirical correction for excess water yields a primary magmatic δ18O range of +6.1‰ to +8.5‰. Variations in δ18O exhibit a compositional dependence, increased δ18O values characterize the evolved samples of the various magmatic series, and δ18O-SiO2 trends are steeper than those predicted for...
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Spinel and garnet fades peridotites from the Vitim Volcanic Field in Siberia comprise a suite of fertile mantle xenoliths, which are LREE depleted and have strongly depleted strontium and neodymium isotopic compositions. Determination of... more
Spinel and garnet fades peridotites from the Vitim Volcanic Field in Siberia comprise a suite of fertile mantle xenoliths, which are LREE depleted and have strongly depleted strontium and neodymium isotopic compositions. Determination of 18O16O ratios by conventional and laser-assisted fluorination techniques yield a very restricted range of whole-rock δ18O values for both spinel peridotites (+ 5.4 to + 5.8‰) and garnet lherzolites (+ 5.5 to + 5.8‰) equivalent to that observed for lunar rocks and midocean ridge basalts (MORB). Mineral δ18O values for the xenoliths are: olivine = + 5.1 to + 5.8%., orthopyroxene = + 5.7 to + 6.0%., clinopyroxene = + 5.5 to + 6.2%., garnet = + 5.5 to +6.0%., and spinel = + 4.9 to + 5.5%. Similarly, δ18O ranges for silicate mineral pairs vary from only 0.5 to 0.7%. The sixteen peridotite xenoliths studied exhibit equilibrium O-isotope fractionations between minerals of a magnitude expected from theoretical and experimental considerations, in particular ...
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VOLCANIC rocks from subduction settings frequently contain 10Be enrichments that have been attributed to sediment subduction1–6, and are often characterized by (238U/230Th) ratios greater than unity, in contrast to mid-ocean-ridge and... more
VOLCANIC rocks from subduction settings frequently contain 10Be enrichments that have been attributed to sediment subduction1–6, and are often characterized by (238U/230Th) ratios greater than unity, in contrast to mid-ocean-ridge and ocean-island basalts7,8. Here we report such an excess of 238U over 230Th in historic lavas from the Southern Volcanic Zone of Chile (33–42° S). The greatest uranium excess is found south of 39° S, where 10Be/9 Be ratios are highest and the trench is filled with sediment. These features suggest that both U and 10Be enrichments result from preferential partitioning of U and Be into a fluid phase during dehydration of the recently subducted sediments. The presence of strong 238U–230Th disequilibria in basaltic magmas of the Southern Volcanic Zone suggests that the timescale for dehydration, melting and eruption in this arc is probably less than ∼20,000 yr.
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The principal deep crustal rock types found at the La Olivina xenolith locality in southeastern Chihuahua, Mexico, are mafic granulites, paragneisses, and intermediate- to silicic-composition orthogneisses. These granulite facies... more
The principal deep crustal rock types found at the La Olivina xenolith locality in southeastern Chihuahua, Mexico, are mafic granulites, paragneisses, and intermediate- to silicic-composition orthogneisses. These granulite facies xenoliths are interpreted in terms of two age groups, pre-Cenozoic and mid-Tertiary, based on previous ion probe dating of zircons from the xenoliths and on isotopic comparisons of the xenoliths to rocks of known age. The mafic granulites have Pb, Nd, and Sr isotopic compositions identical to those of Oligocene volcanic rocks from the La Olivina region. Compositionally, they are olivine-normative gabbroic cumulates, and they precipitated from two or more mid-Tertiary basalt to dacite or rhyolite assimilation/fractional crystallization series. Mineral assemblages in the xenoliths record pressures of ≤7.2 kbar or depths of 35 km thick in Oligocene time as inferred from regional tectonic considerations, then the mafic granulites cannot be samples of basaltic m...
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The Isthmus of Panama comprises a lithologically diverse andesitic oceanic arc of Late Cretaceous to Holocene age; it has large spatial variation in rainfall, displays a large range of physical erosion rates, and, therefore, is an ideal... more
The Isthmus of Panama comprises a lithologically diverse andesitic oceanic arc of Late Cretaceous to Holocene age; it has large spatial variation in rainfall, displays a large range of physical erosion rates, and, therefore, is an ideal location to examine silicate weathering in the tropics. We use a multiyear data set of river chemistry for a 450 km transect across the Cordillera Central of west-central Panama to investigate controls on chemical weathering in tropical small mountainous rivers. Sea-salt corrected cation weathering yields (Casil + Mgsil + Na + K) range over more than an order in magnitude from 3.1 to 31.7 t/km2/yr, while silicate weathering yields (Casil + Mgsil + Na + K + Si) range from 6.9 to 69.5 t/km2/yr. Watershed lithology is the primary control on riverine chemistry, but landscape topographic character and land cover and/or land use also influence solute delivery potential. Strong statistical links of small mountainous river chemical weathering fluxes with rainfall and physical weathering rates attest to the importance of runoff and erosion in maintaining elevated bedrock weathering rates. CO2 consumption ranges from 155 × 103 mol/km2/yr to 1566 × 103 mol/km2/yr, in the upper range of global rates, leading us to suggest that andesite terrains should be considered separately when calculating removal of CO2 from the atmosphere via silicate weathering.
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... pur-pose of this paper is to present such estimates for the age of valley-to-crestline relief in the southern Rocky Mountains of ... of mountain relief obtained by such an approach are approximately accurate only if the relief is... more
... pur-pose of this paper is to present such estimates for the age of valley-to-crestline relief in the southern Rocky Mountains of ... of mountain relief obtained by such an approach are approximately accurate only if the relief is evolving in a broadly equilibrium manner (Hack, 1960), ie ...
Instrumental surveys of coastal profiles in the Cayman Islands, western Caribbean, reveal the presence of a horizontal erosional bench at +1.9 m on Grand Cayman and a deep horizontal notch at +6.4 m on Cayman Brac, but no raised erosional... more
Instrumental surveys of coastal profiles in the Cayman Islands, western Caribbean, reveal the presence of a horizontal erosional bench at +1.9 m on Grand Cayman and a deep horizontal notch at +6.4 m on Cayman Brac, but no raised erosional features on Little Cayman. Each island is surrounded by a horizontal constructional raised reef, usually below +2 m, here dated by U-series methods as 124,000 ± 8000 yr old, and hence broadly contemporary with other western Atlantic raised reefs of similar elevations. The different raised erosional features indicate independent vertical tectonic movement of the three islands, predating the formation of the raised reef. The accordance and horizontality of the raised reef indicates stability of the islands since the last interglacial times. An erosional notch at present sea level has formed since the sea reached its present level less than 2100 B.P., and algal benches on exposed coasts are also in equilibrium with present conditions.
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O-isotope ratios for 127 Cenozoic volcanic rocks from the Andean Cordillera between 5°N and 4°S range from +5.2 to +14.0‰ (SMOW). Lavas from eight volcanoes in the SVZ between 36–42°S exhibit a very narrow range of δ18O values (+5.2 to... more
O-isotope ratios for 127 Cenozoic volcanic rocks from the Andean Cordillera between 5°N and 4°S range from +5.2 to +14.0‰ (SMOW). Lavas from eight volcanoes in the SVZ between 36–42°S exhibit a very narrow range of δ18O values (+5.2 to +6.7‰), with O-isotope variations independent of bulk chemical composition. The highest O-isotope ratios occur in the CVZ where lavas from 16 volcanic centres between 16–26°S have a wide range of δ18O values (+6.9 to +14.0‰), with 18O/16O ratios well correlated with both bulk chemical composition and radiogenic isotope variations at some centres. In the NVZ, between 5°N and 2°S, lavas from nine volcanoes have intermediate O-isotope compositions (δ18O = +6.3 to 7.7‰), which are unrelated to chemical composition. The low 18O/16O ratios for the lavas of the SVZ are most easily explained by derivation from a mantle source, with the parent magmas rising largely unmodified through the thin ( 60 km) continental crust of the region. The intermediate O-isotope character for the lavas of the NVZ suggests that both mantle and crustal sources were important in the petrogenesis of lavas in the region.
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Cave sediments from Stump Cross Cave in northern England contain Pleistocene mammal remains. Uranium-series dating of calcium carbonate deposits closely associated with the fossiliferous horizons has established an absolute age of 83,000... more
Cave sediments from Stump Cross Cave in northern England contain Pleistocene mammal remains. Uranium-series dating of calcium carbonate deposits closely associated with the fossiliferous horizons has established an absolute age of 83,000 ± 6000 yr B.P. for a faunal assemblage largely comprised of wolverines (Gulo gulo). This date lies firmly within the younger portion of oxygen-isotope stage 5. The occurrence of wolverines in the vicinity of Stump Cross Cave at ca. 83,000 yr B.P. indicates a significant climatic deterioration from ca. 120,000 yr B.P., when an Ipswichian interglacial fauna with hippopotamus was present in this part of northern England.
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Over the last 200 Ma, the ensialic Andean plate margin has been characterized by calc-alkaline magmatism. The early (Mesozoic), activity was dominantly of basaltic volcanism while the Cainozoic volcanism was of intermediate, calc-alkaline... more
Over the last 200 Ma, the ensialic Andean plate margin has been characterized by calc-alkaline magmatism. The early (Mesozoic), activity was dominantly of basaltic volcanism while the Cainozoic volcanism was of intermediate, calc-alkaline character. The restriction of Recent volcanism to parts of the Andes underlain by thick wedges of asthenospheric mantle, and the Sr and Nd isotopic relations, indicate that the calc-alkaline parental magmas are derived from the asthenospheric mantle. There is no unequivocal geochemical and geophysical evidence that continental crust or sediment has contributed to the mantle source for Andean magmatism. The chemical compositions of the calc-alkaline volcanic rocks of the active volcanic zones are controlled by fractional crystallization, whereas O-Sr isotopic relations reflect crustal interaction of mantle-derived parental magma with the sialic basement of the Andes. The variable extent of fractional crystallization, partial melting, and mixing of c...
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... 77, 250−275 (1969). | ISI | ChemPort |. 17. Bloom, AL, Broecker, WS, Chappell, JS, Matthews, RK & Mesolella, KJ Quat. Res. 4, 185−205 (1974). | ISI | ChemPort |. 18. Harmon, RS, Schwarcz, HP & Ford, DC Quat. Res. 9, 205−218... more
... 77, 250−275 (1969). | ISI | ChemPort |. 17. Bloom, AL, Broecker, WS, Chappell, JS, Matthews, RK & Mesolella, KJ Quat. Res. 4, 185−205 (1974). | ISI | ChemPort |. 18. Harmon, RS, Schwarcz, HP & Ford, DC Quat. Res. 9, 205−218 (1978). | ISI | ChemPort |. 19. ...
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The Mona Complex exposed on the Llŷn peninsula includes the Sarn Complex, which is a suite of variably-deformed, plutonic igneous rocks (originally mapped partly as gneisses) ranging from gabbro to granite, and an inlier of high-grade... more
The Mona Complex exposed on the Llŷn peninsula includes the Sarn Complex, which is a suite of variably-deformed, plutonic igneous rocks (originally mapped partly as gneisses) ranging from gabbro to granite, and an inlier of high-grade paragneisses. Geochemical data for samples from the Sarn Complex may be divided into two distinct populations. The Rb-Sr data for samples from these geochemical groups define significantly different ages. The older age, 549 ± 19 Ma, initial 87Sr/86Sr 0.7096 ± 3, is identified as the age of intrusion in late Precambrian to Cambrian times, while a younger age of 458 ± 16 Ma may approximate to the age of a resetting event. The Parwyd paragneisses yield an Rb-Sr whole-rock isochron age of 542 ± 17 Ma, concordant with the age of intrusion of the Sarn Complex, with an initial 87Sr/86Sr of 0.7069 ± 4. For the Sarn Complex, δ18O values range from +9.5 to +12.0 per mil (SMOW), and in the Parwyd metasediments from +9.4 to +13.3 per mil. We conclude that the earliest magmatism and metamorphism in the Mona Complex of Llŷn occurred during late Precambrian to Cambrian times, broadly contemporaneous with similar events in Anglesey. The high initial 87Sr/86Sr and high δ18O values for the Sarn Complex are most simply interpreted as reflecting either a crustal source-region or incorporation of a significant proportion of crustal material (such as the Parwyd gneisses) into a mantle-derived magma.
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RS Harmon T.-L. Ku Los Angeles, California 90007 RK Matthews Providence, Rhode Island 02912 PL Smart Limits of U-series analysis ... Hill) terrace, 11s,000f§»ggg yr; Barbados (Kendal Hill) terrace, 210,000 jgqgg yr; Curacao +6 m terrace,... more
RS Harmon T.-L. Ku Los Angeles, California 90007 RK Matthews Providence, Rhode Island 02912 PL Smart Limits of U-series analysis ... Hill) terrace, 11s,000f§»ggg yr; Barbados (Kendal Hill) terrace, 210,000 jgqgg yr; Curacao +6 m terrace, 124,000 yr; Key Largo Limestone ...
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Twelve Laramide intrusions, eleven country rocks, and over thirty hydrothermal minerals from the Central City and Idaho Springs mining districts, Colorado, have been analyzed for Sr isotope compositions. Intrusions have also been analyzed... more
Twelve Laramide intrusions, eleven country rocks, and over thirty hydrothermal minerals from the Central City and Idaho Springs mining districts, Colorado, have been analyzed for Sr isotope compositions. Intrusions have also been analyzed for oxygen isotopes. Precambrian country rocks have an average 87 Sr/ 86 Sr ratio at 59 m.y. ago of ca. 0.73, but with a high degree of local isotopic heterogeneity. Strontium contents and initial ratios in the Laramide intrusions define a roughly hyperbolic array from 0.705 (4,020 ppm Sr) to 0.722 (32 ppm Sr), whereas whole-rock delta 18 O compositions vary from 7.7 to 12.4 per mil (up to 16ppm in carbonate-altered rocks). Various mixing models which might give rise to these compositions are examined. Intermediate rocks probably contain a large fraction of lower crustal Sr, but a mantle-derived component cannot be ruled out. The more evolved quartz bostonites display assimilation processes during fractional crystallization of plagioclase in the upper crust.Hydrothermal sericites and ores have a very wide range of initial Sr isotope ratios (0.708-0.769), which are indicative of varying proportions of Sr from magmatic and country-rock sources contributing to the five different stages of hydrothermal activity. Low initial ratios found in sericite, pyrite, and fluorite from early and late molybdenite stages indicate a large contribution of magmatic Sr and hence possibly of other cations to these hydrothermal fluids. In contrast, the radiogenic Sr characterizing the uraninite, base metal, and late telluride stages is probably derived, along with other cations, from country rocks.
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Ground penetrating radar and thermal sensors hold much promise for the detection of non-metallic land mines. In previous work we have shown that the performance of ground penetrating radar strongly depends on field soil conditions such as... more
Ground penetrating radar and thermal sensors hold much promise for the detection of non-metallic land mines. In previous work we have shown that the performance of ground penetrating radar strongly depends on field soil conditions such as texture, water content, and soil-water salinity since these soil parameters determine the dielectric soil properties. From soil physics and field measurements we know that the performance of thermal sensors also strongly depends on soil texture and water content. There is it critical that field soil ...
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To support a number of projects focused on diverse biological and physical science aspects of the upper Río Chagres basin, a detailed stream network was extracted from digital elevation data obtained by interferometric radar survey. The... more
To support a number of projects focused on diverse biological and physical science aspects of the upper Río Chagres basin, a detailed stream network was extracted from digital elevation data obtained by interferometric radar survey. The elevation data represented the bald earth surface plus a forest canopy of varying height. Therefore, different algorithms for stream network extraction were qualitatively evaluated in terms of their capability to extract accurate stream locations from this challenging type of elevation data. The programs based on a shortest path algorithm and an imposed gradients constraint provided stream locations that were closer to on-ground GPS measurements than the tools based on depressions filling and iterative linking. The influence of different spatial resolutions on network structure and orientation was also explored.
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Laser-induced breakdown spectroscopy (LIBS) is a simple and straightforward technique of atomic emission spectroscopy that can provide multi-element detection and quantification in any material, in-situ and in real time because all... more
Laser-induced breakdown spectroscopy (LIBS) is a simple and straightforward technique of atomic emission spectroscopy that can provide multi-element detection and quantification in any material, in-situ and in real time because all elements emit in the 200–900 nm spectral range of the LIBS optical emission. This study evaluated two practical applications of LIBS—validation of labels assigned to garnets in museum collections and discrimination of LCT (lithium-cesium-tantalum) and NYF (niobium, yttrium and fluorine) pegmatites based on garnet geochemical fingerprinting, both of which could be implemented on site in a museum or field setting with a handheld LIBS analyzer. Major element compositions were determined using electron microprobe analysis for a suite of 208 garnets from 24 countries to determine garnet type. Both commercial laboratory and handheld analyzers were then used to acquire LIBS broadband spectra that were chemometrically processed by partial least squares discrimina...
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Geology and Geochemistry
The ability to rapidly conduct in-situ chemical analysis of multiple samples of soil and other geological materials in the field offers many advantages over a traditional approach that involves collecting samples for subsequent... more
The ability to rapidly conduct in-situ chemical analysis of multiple samples of soil and other geological materials in the field offers many advantages over a traditional approach that involves collecting samples for subsequent examination in the laboratory. This study explores the application of complementary spectroscopic analyzers and a data fusion methodology for the classification/discrimination of >100 soil samples from sites across the United States. Commercially available, handheld analyzers for X-ray fluorescence spectroscopy (XRFS), Raman spectroscopy (RS), and laser-induced breakdown spectroscopy (LIBS) were used to collect data both in the laboratory and in the field. Following a common data pre-processing protocol, principal component analysis (PCA) and partial least squares discriminant analysis (PLSDA) were used to build classification models. The features generated by PLSDA were then used in a hierarchical classification approach to assess the relative advantage o...
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The mineral exploration industry requires new methods and tools to address the challenges of declining mineral reserves and increasing discovery costs. Laser-induced breakdown spectroscopy (LIBS) represents an emerging geochemical tool... more
The mineral exploration industry requires new methods and tools to address the challenges of declining mineral reserves and increasing discovery costs. Laser-induced breakdown spectroscopy (LIBS) represents an emerging geochemical tool for mineral exploration that can provide rapid, in situ, compositional analysis and high-resolution imaging in both laboratory and field and settings. We demonstrate through a review of previously published research and our new results how LIBS can be applied to qualitative element detection for geochemical fingerprinting, sample classification, and discrimination, as well as quantitative geochemical analysis, rock characterization by grain size analysis, and in situ geochemical imaging. LIBS can detect elements with low atomic number (i.e., light elements), some of which are important pathfinder elements for mineral exploration and/or are classified as critical commodities for emerging green technologies. LIBS data can be acquired in situ, facilitati...
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Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley... more
Numerous ephemeral streams flow within the McMurdo Dry Valley Region of Antarctica that transport glacial meltwater to perennially ice-covered, closed-basin lakes during the austral summer. The diurnal behavior for two Taylor Valley streams of different character was examined during the summer of 2010-11. Andersen Creek is a short, 1st-order proglacial stream, whereas Von Guerard Stream is a long, high-order stream with an extensive hyporheic zone that has a substantial cyanobacterial algal mat community in its middle reaches. Both streams display strong daily cycles for temperature, electrical conductivity, dissolved oxygen, and pH. Conductivity varies in concert with flow, with solute dilution occurring during the daily high-flow pulse. Dissolved oxygen co-varies strongly with pH at Andersen Creek but not for Von Guerard Stream. Each stream has a distinct geochemical character that for Andersen Creek is a direct reflection of its glacial source, unmodified by secondary effects, wh...