Longstanding goals of scientific ocean drilling include determining the timing and amplitudes of global sea-level change, as well as the role of eustacy in the generation and preservation of continental margin stratigraphy. However, continental margin sedimentation is a function of both allogenic and autogenic processes, and extracting a eustatic record requires an understanding of local sedimentary processes and their influence on strata formation. IODP Expedition 317 to Canterbury Basin, New Zealand provides an opportunity to identify the regional processes involved in the formation of sedimentary sequences where temporally evolving across-shelf and along-margin sediment sources potentially interact with both eustasy and tectonics to generate margin stratigraphy. This study defines sedimentary petrofacies using petrographic and X-ray diffraction techniques and combines them with lithofacies to characterize sedimentation within unconformity-bounded sequences. Differentiating the relative influence of each sediment source is made possible by the unique aspects of the onshore geology and sediment supplied by the rivers of South Island, New Zealand: in this system sediment composition is a proxy for transport mode/direction, with mica-rich schist detritus being brought in from the south, and graywacke Torlesse detritus from the west. Higher-resolution analyses will target specific seismic sequences from the Pliocene to Recent that represent changing climatic and eustatic conditions. A primary hypothesis tested is that recurring lithofacies motifs that likely formed during high-amplitude Pleistocene sea-level cycles can be linked to sediment provenance, and even where less lithologically distinct, a recognizable signal may remain in the detrital fraction. Another hypothesis is that the formation of Plio- Pleistocene sequences along the Canterbury Margin is strongly influenced by the relative sediment supply from alongshore/shelf (Clutha/Waitaki rivers) versus cross-margin (Rangitata-Ashburton-Rakaia braided system) transport, with the latter becoming more dominant in the later Pleistocene, potentially leading to an autogenic increase in accommodation space that lead to increased sequence preservation. A holistic approach is used to test these hypotheses, similar to that applied in the MARGINS Source-to-Sink focus site on North Island, New Zealand. This methodology links newly acquired data from onshore outcrops, stream and coastal deposits (collected in conjunction with New Zealand colleagues) to Expedition 317 results in order to evaluate potential basin-wide changes in sediment supply and distribution. Temporal changes in the relative timing and routing of sediment to the Canterbury margin are determined from comparisons between the cross-shelf (U1351, U1353, U1354) and the two Canterbury slope sites (ODP Site 1119 and U1352). Discrete mineralogical observations from this study eventually will be compared to and combined with high-resolution elemental and carbonate analyses proposed by Fulthorpe et al. to provide key petrologic and mineralogic constraints on core and seismic data interpretation for the margin, including distinguishing lithologic changes that might correspond to Milankovitch cyclicity. The history of global sea level change and the impact of future sea-level rise related to global warming are one of the foremost issues facing society. Drilling results from the Canterbury Margin represent a key global component of a comprehensive IODP program to extract sea-level information from continental margin stratigraphy. Our data and results will be made publically available through the IODP portal as part of the IODP Sample, Data, and Obligations Policy and through presentations at meetings and publications. This study will provide educational opportunities for a number of high school, undergraduate and graduate students at CSU Northridge and the University of Florida. One high school student from Florida will participate as part of the UF Student Science Training Program (UF-SSTP), a seven-week residential research program for junior and senior-level high schools students considering science careers. Two undergraduate and two graduate students will participate in this project from CSUN and UF, including students from underrepresented groups and it is expected this participation will form the basis for their theses (BS/MS) or dissertation. The project includes an educational outreach program at UF as part of the UF Geogator program that provides presentations to local K-12 programs about Earth and our environment. The program will make the research on global sea-level change accessible to the local Florida community, where rising sea level and the hazards associated with it are a growing societal concern.

El objetivo del Núcleo Milenio Paleoclima es reconstruir los patrones y entender las causas del cambio climático pasado en el Hemisferio Sur (HS), con énfasis en la Patagonia chilena y argentina (40°-55°S). Esta región es ideal para investigar la evolución paleoclimática del tercio sur del mundo, por lo que planificamos estudiar múltiples sensores de variabilidad climática en el pasado a lo largo de transectos norte-sur y este-oeste. Esta zona es estratégica para monitorear componentes clave del sistema climático, dado que es el único continente que intersecta la corriente circumpolar antártica y el cinturón de vientos del oeste. Reconstruir la variabilidad paleoclimática en Patagonia mejorará nuestro entendimiento de las dinámicas climáticas en un sector insuficientemente estudiado del HS, así como la secuencia de eventos y procesos durante transiciones climáticas mayores.

En la presente postulación, se propone la incorporación al Instituto de Ciencias de la Ingeniería de la Universidad de O’Higgins de la Dra. Tania Villaseñor Jorquera quien tiene una trayectoria académica destacada y un plan de docencia e investigación que aporta de forma sustantiva al desarrollo de la institución. La propuesta considera la investigación de procesos de erosión y transporte de sedimento en Chile central en relación al cambio climático y la actividad antrópica. En este proyecto, se monitoreará el flujo de sedimento en diferentes sectores de las cuencas de los ríos Maipo e Itata a través del análisis de proveniencia de sedimento fluvial con el fin de detectar variabilidad en las zonas que aportan sedimento y los mecanismos de transporte desde la cordillera hacia el océano. También se analizarán registros sedimentarios marinos para construir una línea base del funcionamiento de los sistemas sedimentarios en el pasado reciente. Esta línea de investigación tiene impacto directo en problemáticas de la zona centro de Chile, como la erosión, el transporte de contaminantes, procesos de remoción en masa, y propiciará colaboraciones interdisciplinarias entre académicos de la Universidad así como con investigadores de otras instituciones nacionales e internacionales. Esta propuesta de investigación, sumado a la experiencia docente de Tania, fortalecerá el grupo académico del Instituto, en particular el de la carrera de Ingeniería Civil Geológica. Las redes de trabajo internacional de Tania permitirán fortalecer el programa de internacionalización de la Universidad de O’Higgins. Por otra parte, su experiencia en divulgación de la ciencia resulta muy atractivo para potenciar el proceso de vinculación con el medio, de gran importancia para la misión de la Universidad. Todos estos aspectos contribuirán de forma importante a la proyección de la Universidad de O’Higgins como referente científico y académico para la región y el país.

The aim of this proposal is to develop a high-resolution (interdecadal) quantitative reconstruction of
SWW intensity variability over SSA during the Late Pleistocene-Holocene, based on the analysis of aeolian
lithic particles deposited in a closed-basin lake. With this reconstruction we expect to answer this question:
Are the different proxies responding synchronously to the SWW changes? if not, what other
factors may be influencing the record? What is the maximum time delay between proxies?, and
what is the resolution necessary to see this lag? Addressing this issue in the study of the dynamics of
SWW during the Late Pleistocene-Holocene will contribute to reconcile conflicting interpretations of SWW
based on different climate proxies in Patagonia. For this, this quantitative reconstruction will be accompanied by the reconstruction of precipitation changes– associated to SWW dynamics – using indirect proxies: pollen analyses in the same lacustrine sediments,and the study of a fjord sedimentary record to evaluate changes in sediment runoff. The comparison of direct and indirect proxies of changes in SWW activity from two different locations in the study area will permit to evaluate 1) local versus regional changes in environmental conditions, and 2) timing and lag between the different proxies and other climate records of the region (for example, Antarctic climate records). Our results will provide important insights into paleoclimatic dynamics of SSA by improving previous qualitative reconstructions for this belt and helping to decipher the magnitude and timing of SWW past intensity changes. This will support current efforts to better understand future climate projections in the region and adequately assess mitigation strategies against its effects.

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Sediment routing systems link the fate of sediment from source to sink in relation to the processes of sediment generation, transport and storage that take place at or near the surface. The transfer of sediment within the sediment routing system involves a cascade of sediment from erosional source areas to depositional sinks in which sediment connectivity between different compartments of the landscape modulate sediment pathways at different scales of space and time. Fluvial systems and transport of suspended sediment are key elements in the transfer of sediment across landscapes and their workings are being altered by climate change and human intervention. In central Chile (30º-37ºS) a decade-long drought is resulting in reduced water discharge, glacier retreat, and diminished sediment discharge to the ocean. The later reflects changing sediment dynamics within the fluvial basins of this region.
In this project the temporal and spatial variability of sediment sources and pathways will be studied in the El Volcán River Basin (33ºS), a mountain catchment tributary to the Maipo River, during two consecutive high runoff periods (October-March; 2022-2023 and 2023-2024), with the goal to evaluate interannual and seasonal variations in sediment connectivity in the El Volcán River Basin by identifying the areas of the basin that feed sediment to the fluvial system and describe which pathways of sediment operate under changing flow conditions. Considering the hydrological and sedimentological regime of the mountain catchments in central Chile, the working hypothesis of this proposal is that sediment connectivity in the fluvial system varies throughout seasons as the flow regime, source of runoff, and sediment sources fluctuate from spring to late summer. The variability of the bedrock geology in this basin provides favorable conditions to use sediment provenance techniques to study sediment production and transfer from source to sink at the seasonal and interannual scale.
The investigation will start with a geomorphological analysis of the basin that will allow the identification of potential sediment sources (alluvial fans and cones, scree slopes, gullies, fluvial terraces, landslides, etc), which will be consequently sampled. Suspended sediment will be sampled in different parts of this basin during two seasons of high runoff, from the upper tributaries to the catchment’s outlet. Sediment provenance will be analyzed in all suspended sediment samples in order to track sediment sources and pathways. Geochemistry (major and trace elements) is a widely used method to infer sediment provenance in continental environments. Fallout radionuclides (137Cs, 210Pb) are efficiently fixed in fine sediment particles and their activities are independent of lithology and soil type. Therefore, their activities are different in surficial and subsurface sources as well as in recently exposed land or in zones with variable erosion rates. Geochemistry and fallout radionuclides will be measured in the suspended sediment samples and will be compared to the same properties measured in all potential sediment sources within this basin. The compositional results will be analyzed using mixing models in order to establish the relative contribution of each of the potential sources over time.
With the study of sediment provenance at seasonal and interannual scales in the El Volcán River Basin it is expected to i) determine temporal and spatial variation in the sources that supply sediment, and therefore the zones within the basin that produce sediment: low, medium, or high El Volcán River Basin, ii) evaluate the erosion processes of the surface (sheet or reel erosion) or subsurface (stream banks, gullies) that participate in the mobilization of sediment to the river, iii) establish variations in the transfer of the sediment provenance signal in this catchment (cascade of sediment from source to sink), iv) evaluate interannual variability of these processes, and v) build a conceptual model of sediment connectivity in this basin during changing flow conditions. The results of this investigation will provide insights into the processes that modulate sediment transport in the Maipo Basin, which is relevant considering the frequent episodes of high turbidity in this river. Moreover, the results could help to forecast the potential influence of projected hydroclimatic changes and anthropogenic activity in central Chile on particle fluxes across the Andes and resultant morphological and sedimentary adjustment of fluvial basins as the sediment is transferred from mountain source to ocean sink.

Sistema Articulado de Investigación en Cambio Climático y Sustentabilidad de Zonas Costeras de Chile CUECH/RISUE RED21992