Leaf photosynthetic measurements using a portable 14Co2 field system were carried out and correlative leaf relative growth rates, RGR, were determined at different leaf positions of three alpine plant species throughout the growing season. Initially there was a period of high leaf RGR associated with a period of increasing photosynthetic activity. Following this stage was a long period of no net change in length of the living leaf. During this period, photosynthetic activity generally increased to a maximum level and then decreased steadily. The final ontogenetic stage was a period of negative leaf RGR denoting leaf senescence which was associated with a marked decline in leaf Co2 uptake. Ontogenetic timing of these alpine species is geared with the surge and decline of individual leaf photosynthetic activity so that one to several leaves operating at near maximal photosynthetic capacity are always maintained during the growing season for each plant. These findings are discussed in relation to their adaptive significance for these species.

The Alpine Fault is the major structure of the Pacific-Australian plate boundary through New Zealand�s South Island. During dextral reverse fault slip, a <5 million year old, ~1 km thick mylonite zone has been exhumed in the hanging-wall, providing unique exposure of material deformed to very high strains at deep crustal levels under boundary conditions constrained by present-day plate motions. The purpose of this study was to investigate the fault zone rheology and mechanisms of strain localisation, to obtain further information about how the structural development of this shear zone relates to the kinematic and thermal boundary constraints, and to investigate the mechanisms by which the viscously deforming mylonite zone is linked to the brittle structure, that fails episodically causing large earthquakes. This study has focussed on the central section of the fault from Harihari to Fox Glacier. In this area, mylonites derived from a quartzofeldspathic Alpine Schist protolith are most common, but slivers of Western Province-derived footwall material, which can be differentiated using mineralogy and bulk rock geochemistry, were also incorporated into the fault zone. These footwall-derived mylonites are increasingly common towards the north. At amphibolite-facies conditions mylonitic deformation was localised to the mylonite and ultramylonite subzones of the schist-derived mylonites. Most deformation was accommodated by dislocation creep of quartz, which developed strong Y-maximum crystallographic preferred orientation (CPO) patterns by prism (a) dominant slip. Formation of this highly-oriented fabric would have led to significant geometric softening and enhanced strain localisation. During this high strain deformation, pre-existing Alpine Schist fabrics in polyphase rocks were reconstituted to relatively well-mixed, finer-grained aggregates. As a result of this fabric homogenisation, strong syn-mylonitic object lineations were not formed. Strain models show that weak lineations trending towards ~090� and kinematic directions indicated by asymmetric fabrics and CPO pattern symmetry could have formed during pure shear stretches up-dip of the fault of ~3.5, coupled with simple shear strains [greater than or equal to]30. The preferred estimate of simple:pure shear strain gives a kinematc vorticity number, W[k] [greater than or equal to]̲ 0.9997. Rapid exhumation due to fault slip resulted in advection of crustal isotherms. New thermobarometric and fluid inclusion analyses from fault zone materials allow the thermal gradient along an uplift path in the fault rocks to be more precisely defined than previously. Fluid inclusion data indicate temperatures of 325+̲15�C were experienced at depths of ~45 km, so that a high thermal gradient of ~75�C km⁻� is indicated in the near-surface. This gradient must fall off to [ less than approximately]l0�C km⁻� below the brittle-viscous transition since feldspar thermobarometry, Ti-inbiotite thermometry and the absence of prism(c)-slip quartz CPO fabrics indicate deformation temperatures did not exceed ~ 650�C at [greater than or equal to] 7.0-8.5�1.5 kbar, ie. 26-33 km depth. During exhumation, the strongly oriented quartzite fabrics were not favourably oriented for activation of the lower temperature basal(a) slip system, which should have dominated at depths [less than approximately]20 km. Quartz continued to deform by crystal-plastic mechanisms to shallow levels. However, pure dislocation creep of quartz was replaced by a frictional-viscous deformation mechanism of sliding on weak mica basal planes coupled with dislocation creep of quartz. Such frictional-viscous flow is particularly favoured during high-strain rate events as might be expected during rupture of the overlying brittle fault zone. Maximum flow stresses supported by this mechanism are ~65 Mpa, similar to those indicated by recrystallised grain size paleopiezometry of quartz (D>25[mu]m, indicating [Delta][sigma][max] ~55 MPa for most mylonites). It is likely that the preferentially oriented prism (a) slip system was activated during these events, so the Y-maximum CPO fabrics were preserved. Simple numerical models show that activation of this slip system is favoured over the basal (a) system, which has a lower critical resolved shear stress (CRSS) at low temperatures, for aggregates with strong Y-maximum orientations. Absence of pervasive crystal-plastic deformation of micas and feldspars during activation of this mechanism also resulted in preservation of mineral chemistries from the highest grades of mylonitic deformation (ie. amphibolite-facies). Retrograde, epidote-amphibolite to greenschist-facies mineral assemblages were pervasively developed in ultramylonites and cataclasites immediately adjacent to the fault core and in footwall-derived mylonites, perhaps during episodic transfer of this material into and subsequently out of the cooler footwall block. In the more distal protomylonites, retrograde assemblages were locally developed along shear bands that also accommodated most of the mylonitic deformation in these rocks. Ti-in-biotite thermometry suggests biotite in these shear bands equilibrated down to ~500+̲50�C, suggesting crystal-plastic deformation of this mineral continued to these temperatures. Crossed-girdle quartz CPO fabrics were formed in these protomylonites by basal (a) dominant slip, indicating a strongly oriented fabric had not previously formed at depth due to the relatively small strains, and that dislocation creep of quartz continued at depths [less than or equal to]20 km. Lineation orientations, CPO fabric symmetry and shear-band fabrics in these protomylonites are consistent with a smaller simple:pure shear strain ratio than that observed closer to the fault core (W[k] [greater than approximately] 0.98), but require a similar total pure shear component. Furthermore, they indicate an increase in the simple shear component with time, consistent with incorporation of new hanging-wall material into the fault zone. Pre-existing lineations were only slowly rotated into coincidence with the mylonitic simple shear direction in the shear bands since they lay close to the simple shear plane, and inherited orientations were not destroyed until large finite strains (<100) were achieved. As the fault rocks were exhumed through the brittle-viscous transition, they experienced localised brittle shear failures. These small-scale seismic events formed friction melts (ie. pseudotachylytes). The volume of pseudotachylyte produced is related to host rock mineralogy (more melt in host rocks containing hydrated minerals), and fabric (more melt in isotropic host rocks). Frictional melting also occurred within cataclastic hosts, indicating the cataclasites around the principal slip surface of the Alpine Fault were produced by multiple episodes of discrete shear rather than distributed cataclastic flow. Pseudotachylytes were also formed in the presence of fluids, suggesting relatively high fault gouge permeabilities were transiently attained, probably during large earthquakes. Frictional melting contributed to formation of phyllosilicate-rich fault gouges, weakening the brittle structure and promoting slip localisation. The location of faulting and pseudotachylyte formation, and the strength of the fault in the brittle regime were strongly influenced by cyclic hydrothermal cementation processes. A thermomechanical model of the central Alpine Fault zone has been defined using the results of this study. The mylonites represent a localised zone of high simple shear strain, embedded in a crustal block that underwent bulk pure shear. The boundaries of the simple shear zone moved into the surrounding material with time. This means that the exhumed sequence does not represent a simple 'time slice' illustrating progressive fault rock development during increasing simple shear strains. The deformation history of the mylonites at deep crustal P-T conditions had a profound influence on subsequent deformation mechanisms and fabric development during exhumation.

<p>Lake sediments are frequently used as archives of climate and environmental change. Minerogenic sediment variability in alpine lakes is often used to reconstruct past glacier and slope process activity. Alpine lake sediments can however have many different origins, which may induce errors in paleoenvironmental reconstructions. The aim of this project was to enhance the understanding of minerogenic lake sedimentation in alpine lakes and improve their use as environmental archives.</p><p>Catchment geomorphology and Holocene sediment sequences were analysed for five alpine lakes. Several minerogenic sediment sources were detected in catchments and sediment sequences. Slope-, fluvial-, periglacial-, nival- and aeolian sediment transportation processes contribute to create complex lake sediment patterns. Large variations in sedimentation rates were discovered within and between lakes, which has implications for sampling strategies and age-model constructions. Similar fine-grained minerogenic laminations were found in four of the investigated lakes, despite large differences in setting. The demonstrated similarity between glacial and non-glacial lakes may complicate interpretations of glaciolacustrine sediment signals.</p><p>The main conclusion is that lake sedimentation in alpine environments is highly dependent on several geomorphological factors. All lakes should therefore be viewed as unique and the geomorphology should be thoroughly investigated before environmental reconstructions are based on lake sediment proxies. This study has confirmed the multi-source origin of alpine lake sediment, which also opens possibilities of more multi-faceted paleoenvironmental studies. Different process-proxies could potentially be used to separate different climate signals, e.g. precipitation, temperature and wind, in lake sediments. Analysis of grain-size distribution, detailed mineralogy and magnetic mineralogy in combination with X-ray radiography are suggested methods for such reconstructions.</p>

La couverture paléogène du Pelvoux (zone externe des Alpes occidentales françaises) a été étudiée du col du Lautaret au Champsaur oriental. Une analyse séquentielle, une étude des micro faciès et des microfaunes ont été réalisées sur 49 coupes complètes levées dans cette région après qu'une cartographie détaillée en ait été dressée. Une analyse structurale fine et une étude géochimique ont complété l'examen de quelques secteurs . .\ :. La trilogie nummulitique (dépôts successifs de sédiments de nature calcaire puis marneuse et enfin gréseuse) est transgressive sur le socle cristallin du Pelvoux ou sur des lambeaux de Mésozoïque conservés malgré les érosions antérieures. La découverte d'une microfaune bartonienne dans le SE du massif (où le plus souvent la base du Paléogène est priabonienne) et les reconstitutions paléogéographiques que nous avons effectuées, permettent de cerner le diachronisme de la transgression qui chemine du S vers le N et d'E .Un détritisme omniprésent se manifeste dans la série,provoqué par deux facteurs : 1- une alimentation en débris fins provenant, d'une part, des affleurements de Cristallin constituant à l'époque un Pelvoux embryonnaire, et d'autre part, des nappes internes qui se mettent en place dans la partie orientale du bassin marin tertiaire. 2- une alimentation en détritiques grossiers,d'origine très locale et liée à l'existence de fractures à jeu synsédimentaire Nl70-l8O. L'héritage structural triasique, liasique, néocrétacé et/ou paléocène, joue un rôle fondamental dans la paléogéographie éocène de cette région, comme d'ailleurs lors de la structuration postnummulitique du Pelvoux. Il consiste plus particulièrement en une fracturation probablement issue du rifting téthysien (N30- 40 et NI70- I8O) et, à l'E, par la reprise en chevauchement avant le Nummulitique, de grands accidents subméridiens tel celui du rocher de l'Vret. La situation géographique de ce dernier au front du poinçon que représente le Pelvoux, a permis son écaillage postérieurement au dépôt des sédiments tertiaires. Au SE, on observe la reprise dextre de fractures N50- 60, le faisceau des Grésourières qui s'engagent dans l'accident d'Ailefroide (N30-40) dont le jeu décrochant permet le chevauchement du Sirac vers l'WSW sur le synclinal de Morges . Ces déformations s'accompagent d'un train de plis dans les Grès du Champsaur, d'une schistosité de flux et d'un étirement des Marnes nummulitiques qui constituent un niveau au décollement privilégié dans la série tertiaire, et enfin de dissolutions importantes dans les calcaires nummulitiques. Tous ces phénomènes sont essentiellement liés à la progression des nappes internes versl'extérieur de l'orogène . Ils sont beaucoup plus discrets au N où l'on note seulement le jeu sénestre du faisceaude failles du Lautaret N110, symétrique de celui de Grésourières, au sud du poinçon du Pelvoux.

Two examples of Pacific rim plate boundary deformation are presented. In the first part of the thesis crustal models are derived for the northwestern part of the Vizcaino block in California using marine seismic and gravity data collected by the Mendocino Triple Junction Seismic Experiment. A northwest-southeast trending kink in the Moho is imaged and interpreted to have formed under compression by reactivation of preexisting thrust faults in the paleoaccretionary prism at the seaward margin of the Vizcaino block. The study suggests that the deformation resulted from mainly north-south compression between the Pacific-Juan de Fuca plates across the Mendocino transform fault and predates late Pliocene Pacific-North America plate convergence. In the second part, 195 earthquakes recorded during the duration of the Southern Alps Passive Seismic Experiment (SAPSE) are analysed. Precise earthquake locations and focal mechanisms provide unprecedented detail of the seismotectonics in the central South Island. The short term (6 month) SAPSE seismicity is compared with long term (8 years) seismicity recorded by the New Zealand National Seismic network and the Lake Pukaki network. The seismicity rate of the Alpine fault is low, but comparable to locked sections of the San Andreas fault, with large earthquakes expected. Changes of the depth of the seismogenic zone, generally uniform at about 10-12 km, occur only localised over distances smaller than 30 km, suggesting that thermal perturbations must be of similar scale. This implies that the thermal effects of the uplift of the Southern Alps do not change the seismogenic depth significantly and are not in accordance with most of the present thermal models. Both the Hope and Porters Pass fault zones are seismically active and deformation is accommodated near the fault zones and in the adjacent crust. North of Mt Cook, a triangular shaped region along the Alpine fault is characterised by absence of earthquakes. We interpret this as the result of the plate boundary shift from the Alpine fault to the Hope and Porters Pass fault zones. The study region shows distributed deformation in a 60-100 km wide zone on NNE-SSW trending thrust faults and strike-slip mechanisms on transfer faults. / Graduation date: 2000 / Best scan available for black and white figures.

Lake sediments are frequently used as archives of climate and environmental change. Minerogenic sediment variability in alpine lakes is often used to reconstruct past glacier and slope process activity. Alpine lake sediments can however have many different origins, which may induce errors in paleoenvironmental reconstructions. The aim of this project was to enhance the understanding of minerogenic lake sedimentation in alpine lakes and improve their use as environmental archives. Catchment geomorphology and Holocene sediment sequences were analysed for five alpine lakes. Several minerogenic sediment sources were detected in catchments and sediment sequences. Slope-, fluvial-, periglacial-, nival- and aeolian sediment transportation processes contribute to create complex lake sediment patterns. Large variations in sedimentation rates were discovered within and between lakes, which has implications for sampling strategies and age-model constructions. Similar fine-grained minerogenic laminations were found in four of the investigated lakes, despite large differences in setting. The demonstrated similarity between glacial and non-glacial lakes may complicate interpretations of glaciolacustrine sediment signals. The main conclusion is that lake sedimentation in alpine environments is highly dependent on several geomorphological factors. All lakes should therefore be viewed as unique and the geomorphology should be thoroughly investigated before environmental reconstructions are based on lake sediment proxies. This study has confirmed the multi-source origin of alpine lake sediment, which also opens possibilities of more multi-faceted paleoenvironmental studies. Different process-proxies could potentially be used to separate different climate signals, e.g. precipitation, temperature and wind, in lake sediments. Analysis of grain-size distribution, detailed mineralogy and magnetic mineralogy in combination with X-ray radiography are suggested methods for such reconstructions.

Décrit comme formant un mégabloc séparé des domaines subbriançonnais et piémontais voisins par des discontinuités de 1er ordre, le domaine briançonnais constituait un élément majeur de la paléomarge nord téthysienne créée par le rifting téthysien. Après son émersion généralisée durant la période du Lias supérieur - Dogger inférieur correspondant à l'étape du rifting, il a subi, au début du Malm, un affaissement brutal se traduisant par le passage à une sédimentation pélagique post-riftlng. Cette sédlmentation qui s'est poursuivie jusque durant l'Eocène inférieur a été cependant troublée par deux crises tectoniques majeures (Callovo-Oxfordien et Vracono-Turonien), dont les causes peuvent être reliées à des processus plus généraux tenant d'abord de l'ouverture de la Téthys ligure, puis de sa fermeture. La crise tectonique du Callovo-Oxfordien résulte de l'effondrement de la marge nord-téthysienne corrélativement au début de l'ouverture océanique dans le domaine liguro-piémontais et elle s'est manifestée en domaine briançonnais par le dépôt d'accumulations détritiques grossieres (olistolites et bréches) soulignant le rejeu distensif d'accidents synsédimentaires subméridiens et transverses qui, hérités du rifting tethyslen, ont induit une différenciation morphologique du mégabloc briançonnais en créant un système de silIons et de plateaux séparés par des pentes. De fait, à partir du Malm, le domaine briançonnals montrait des aires de sédimentation d'orientation subméridiennal qui, séparées les unes des autres par des accidents de 2eme ordre, étaient segmentées en lanières de moindre dimension par des failles de 3eme ordre et découpées en compartiments par des failles synsédimentaires transverses induisant de probables décalages dont l'ampleur et le sens ne peuvent être déterminés. La crise tectonique du Crétacé "moyen" et du début du Crétacé supérieur (Vracono-Turonien), par ailleurs enregistrée sur l'ensemble du domaine alpin , est l'écho de la fermeture de la Téthys ligure dont les modalités, bien que discutées, pourraient être celles d'un stade de subduction de la Téthys ligure vers l'Est ou le Sud-Est sous la marge sud-alpine (subduction "B"), accompagné ou précédé de la mise en place des ophiolites, puis d'un stade de subduction "A" durant lequel la partie la plus interne de la marge passive nord-téthysienne (massif cristallin interne de Dora Maira) subirait un début d'enfoncement dans la zone de subduction. Durant cette crise tectonique et alors que dans le domaine Iiguro-piémontais en cours de tectonisation se déposaient les flyschs à Helminthoides, que le domaine ultrabriançonnais formait une dépression recevant une importante sédimentation détritique (brèches, olistolites et faciès reconstitués) et que le domaine subbriançonnais constituait un sillon au front du domaine briançonnais surélevé et recevait des brèches et des flyschs précoces, le domaine briançonnais se présentait sous la forme d'un bassin "perché" qui était soumis à une sédimentation pélagique ou hémipélagique troublée par la mise en place d'accumulations détritiques surtout grossières (brèches, olistolites et calcschistes farcis). Daté du Vracono-Sénonien inférieur, ce détritisme a souligné le rejeu d'accidents synsédimentaires d'orientation actuelle N 160°E (faille de Queyrellin-Tête Noire et accidents transverses majeurs (faille de Roche Colombe-Beraude, faille des Arêtes de la Bruyère Châtelard, faisceau de failles de la Pisse, etc, ... ), ou plus mineurs (failles du Clot des Vaches, de l'Aiguillette du Lauzet , etc, ...). Ces accidents transverses ont clairement contrôlé la répartition des sédiments détritiques, soit directement (destruction de reliefs transverses), soit indirectement, en individualisant des compartiments plus ou moins hauts qui, différentiellement érodés et sédimentés, ont reçu un détritisme plus ou moins abondant. Cependant, si l'image morphologique présentée par le domaine briançonnais durant le Crétacé supérieur était celle d'un système de sillons, de pentes et de hauts-fonds d'orientation subméridienne dilacérés par des accidents transverses et si le fait que les accumulations détritiques étaient produites par des écroulements localisés de reliefs et par des glissements affectant des pentes, le contexte tectonique de mise en lace de ces sédiments détritiques n'a pu être définie avec précision. De fait et en plus d'une étude comparative avec l'ensemble du détritisme nord*téthyslen, ont été effectuées des comparaisons avec les accumulations détritiques actuelles déposées sur des marges continentales placées dans différents contextes géodynamiques (marges de divergence, marges transformantes et marges actives) . Ces recherches ont conduit à la présentation de modèle de détritisme actuel en régime distensif, coulissant et compressif et ont permis de préciser que les sédiments détritiques néocrétacés briançonnais présentaient une organisation identique aux accumulations détritiques sédimentées en régime distensif. Dans le cadre globalement compressif voyant la résorption de la Téthys ligure, cette crise tectonique distensive tardive affectant le domaine briançonnais trouve parfaitement sa place, car ce rejeu en distension des accidents synsédimentaires traduirait un bombement extensif qui, s'effectuant au droit du Briançonnais, résulterait d'une flexuration élastique de la croûte continentale amincie de la marge nord-téthysienne en avant de la zone enregistrant la subduction et les compressions pareillement à ce qui peut être observé dans les systèmes actuels en subduction. Enfin, comme le confirment la poursuite de la sédimentation hémipélagique sans détritisme grossier sur le domaine briançonnais et l'évolution des phénomènes compressifs dans le temps et dans l'espace, cette situation de bassin "perché" briançonnais bordé par deux zones en dépression s'est clairement prolongée jusqu'à l'Eocène inférieur, et ce n'est qu'à l'Eocène moyen que vont apparaître les premiers flyschs (flyschs noirs lutétiens), dont le dépôt sera stoppé par la mise en place de la nappe des flyschs à Helminthoides de l'Autapie, indiquant les premiers stades de la collision continentale.

This research focuses on documenting and analyzing the factors that affect mountain climbing in the state of Colorado and assessing the potential environmental impacts caused by the growing number of climbers visiting the Fourteeners—the 58 mountain peaks located within the Rocky Mountains exceeding an elevation of 14,000 feet. Key objectives were to: 1. identify factors that have a significant effect on mountain climbing frequency; 2. collect information from physical trail and route evaluation to develop an interim classification index; 3. combine relevant variables to formulate a composite Fourteeners Environmental Degradation Index (FEDI) and use it to evaluate, rank, and compare the 58 fourteeners within the six major mountain ranges; and 4. examine sensitivity of this composite index based on changing relative importance of the input variables. Results from the first phase, based on statistical tests, indicated that annual climbing frequency has a significant positive association with (a) distance from Denver; (b) direct distance from the summit to the nearest paved road; (c) length of the trail/route; and (d) climbing route difficulty. Elevation of a peak’s trailhead, however, is the only variable with a significantly negative relationship with climbing frequency of the fourteeners. The second phase of the study involved the assessment of adverse impacts (trail erosion and trail status) through extensive fieldwork. The data was used to develop an interim FEDI. Peaks in the Front Range (e.g., Mount Evans, Longs Peak, and Pikes Peak) indicate the most adverse human-environmental impacts. Variables from both previous phases were combined to develop the final FEDI. Analyses indicated that Mount Evans (Front Range) was ranked highest (highest level of adverse impacts), while Culebra (Sangre de Cristo Range) ranked lowest. The mountain ranges closest to Denver (Front Range and Tenmile/Mosquito) yielded the highest average ranks, while ranges farthest from Denver showed lowest ranks. Sensitivity analyses of the FEDI suggested that rankings were not drastically altered by adjusting relative importance of input factors. The findings provide important insights on identifying preservation needs within heavily visited mountain environments and can be used to guide future protection efforts, trail construction, and maintenance for existing trails and routes.

Recent climate changes show that the historical record is not an appropriate analog for future climate conditions. This understanding calls into question management decisions that assume climate stationarity and consequently the demand for climate information has increased in order to help frame climate risk more accurately. However, deficits in knowledge about climate impacts and weak connections between existing information and resource managers are two barriers to effective incorporation of climate information in resource management, development, risk management, and other climate-sensitive decisions. In research presented here, I showcase results that address knowledge gaps in the impact of climate on glacial resources in Bolivia, South America. I present a mixing model analysis using isotopic and anion tracers to estimate that glacial meltwater contributed about 50% of the water to streams and reservoirs in La Paz region of Bolivia during the 2011 wet and 2012 dry seasons. To assess how future warming may impact water supplies, I develop a temperature-driven empirical model to estimated changes in a future glacial area. Surface temperature changes were extracted from a multi-model ensemble of global climate models produced for the latest Intergovernmental Panel on Climate Change (IPCC) fifth assessment report and for two greenhouse gas emission scenarios. In both scenarios, declines in glacial area are substantial. For many small glaciers, temperatures at the toe of each glacier rise above the glacier's maximum elevation by 2050 suggesting that water resources will be substantially impacted with continued warming. While these results address a knowledge gap, the extent to which they inform resource management is unknown because the research was conducted without an explicit connection to resource management. Information produced in this fashion is generally acknowledged as being less immediately useful for decision-making because of access and comprehension barriers. These challenges may be mollified, however, with information management strategies. Therefore, I present results from an experiment to see if translating and contextualizing existing climate-related information - information produced similarly to the glacier results highlighted above - help facilitate its use. During a drought afflicted period in Arizona and New Mexico, a monthly synthesis of climate impacts information was disseminated to more than 1400 people. Survey responses from 117 people who consulted the information indicated that the majority of them made at least one drought-related decision and the information in the synthesis at least moderately influenced the majority of those decisions. In addition, more than 90% of the survey respondents indicated that the synthesis improved their understanding of climate and drought; it also helped the majority of them better prepare for drought. The results demonstrate that routine interpretation and synthesis of existing climate information can help enhance access to and understanding of climate information.

Inverse geochemical modelling has been used frequently in groundwater systems between wells along a known flowpath and between precipitation and stream waters in catchments. This research expands the use of inverse geochemical modelling through a reaction path model (RPM) between waters in an alpine catchment to determine the geochemical connections and disconnections within the catchment. The data for this study are from the Green Lake 4 catchment in the Colorado Front Range during the 1996 snowmelt season, which has been divided into discrete time intervals based on snowmelt hydrology. Unique combinations of geochemical connections occur during these time intervals, and they show a dynamic hydrologic system. RPM results show notable disconnections; soil water is not geochemically connected to any other end member. These changes reflect changes in weathering reactions in the catchment that are dependent on the duration and timing of snowmelt. Previously end-member mixture analysis (EMMA) models have been used to discern the water sources in catchments. The combination of RPM and EMMA approaches offers the opportunity to connect the source of water to the internal hydrologic structure of the catchment, to better understand how catchments might respond to changes in climate or atmospheric deposition.