IRTG-StRATEGy - Long Term

163-G 2.2

henry.wichura — Thu, 16 Jun 2016 15:57:50 +0000

Multiple basin filling and excavation cycles and fault reactivation

Working Package:

Temporal Process:

Prof. Manfred Strecker, Ph.D.Potsdam University Prof. Dr. Ricardo AlonsoSalta University (ARG)Prof. Dr. Fernando HongnSalta University (ARG)

163-G 4.1

Anonymous — Fri, 25 Sep 2015 10:16:27 +0000

10|2018 – 09|2021

Magmatic processes, fluid-rock interaction and provenance of Nb-Ta and REE mineralizations in NW Argentina

M.Sc. Enrico RibackiUniversity of Potsdam apl. Prof. Dr. Uwe AltenbergerPotsdam University Dr. Robert TrumbullGFZ Potsdam Dr. Volker LüdersGFZ Potsdam Prof. Dr. Monica López de LuchiBuenos Aires University (ARG)Dr. Raúl LiraMuseum of Mineralogy Córdoba (ARG)Dr. Clara CisternaTucumán University (ARG)Dr. José Pablo LopezTucumán University (ARG)Raúl Becchio, Ph.D.Salta National University (ARG)

Deep-seated processes in the Andean crust, now exposed by tectonics and erosion in the foreland, are integral parts of the resource-forming systems under investigation. After recycling of continental crust by partial melting and magmatism, hydrothermal fluids of magmatic and/or meteoric origin are key agents for a range of processes that form and modify metallic ore deposits. This project will investigate a range of granite-pegmatite related rare earth element (REE) and Sn-Ta-Nb-Li mineralization types in the San Luis range of NW Argentina. The goals are to assess the relative influence of magma composition, particularly the S-type vs. A-type granite composition, in the metals enrichment, and to determine the role of fluids in mineralization. We will concentrate on well-characterised metamorphic complexes and their intruding granitoids of the San-Luis range (Eastern Sierras Pampeanas), where compositionally distinct pegmatites occur: predominantly intragranitic mostly Ordovician Nb-Y-F pegmatites related to water-poor and fluorine-rich melts and mostly Ordovician Li-Cs-Ta pegmatites related to water-rich peraluminous melts and emplaced either in the metamorphic complexes or in their intruding granitoids. These will be compared with similar occurrences further north in Sierras Pampeanas. A small but significant part of the work will follow the alteration of the NYF pegmatites to obtain proxies for provenance studies of critical elements (source to sink) and the research will also help constraining the sources of granite magmas and the role of the interplaying between recycling of continental crust and juvenile additions.

10|2015 – 09|2018

Provenance and transport of Sn (Nb-Ta) and REE from the pre-Andean crustal basement: primary mineralization and secondary enrichment processes

This project will investigate the primary source rocks for Sn (and Nb-Ta) and rare earth elements (REE) in the pre-Andean basement rocks (granites, pegmatites, metamorphic complexes) and the enrichment/mobilization processes related to chemical (hydrothermal alteration or weathering) and mechanical processes (ductile or brittle deformation in fractures and ductile shear zones). The investigation will focus on selected field occurrences of Palaeozoic granites, pegmatites, and their highly deformed metamorphic equivalents of the pre-Andean crustal basement, especially of the Salta Province. For the REE minerals especially (carbonates, phosphates, fluor-carbonates, oxides), there is substantial redistribution related to solubility-reprecipitation processes in the deep crust (e.g. lode deposits in shear zones) as well as surface adsorption in weathered exposures (e.g. heavy REE enrichment in clays: Longnan-type deposits). Because tin minerals and coltan (Nb-Ta ore) from pegmatite fields are commonly mined in alluvium (placers), it is critically important to understand how secondary processes (alteration, chemical and mechanical weathering) affect the criteria used for provenance identification. Therefore, the major aim of the project will be to analyse the origin and enrichment processes of the rare elements in primary (magmatic) as well as in secondary (fluid- and structurally controlled) environments. Emphasis will fall on studies in Salta province, because of the geological situation, including rare element pegmatites, and the direct links with project [G 2.2] working on the reactivation of fault zones and project [G 3.5], which addresses the role of basement composition for metal enrichment in near-surface volcano-tectonic complexes. Close collaboration with project [G 4.2] and the Argentine metallogenesis projects will extend the scope of investigation to places best suited to study the relevant processes (e.g., shear zones, alteration/weathering profiles, etc.). The research will combine modern techniques of mineralogical, microstructural and (isotope) geochemical analysis with field campaigns to examine key localities best suited to study the chemical and mechanical alteration of primary mineralization. The relevance of this study is in the field of mineral exploration primarily, i.e., for orogenic structurally-controlled REE deposits, and also for the growing field of provenance certification to control conflict ores.

Working Package:

WP4 - Georesources

Temporal Process:

Long Term

M.Sc. Melanie LorenzPotsdam University apl. Prof. Dr. Uwe AltenbergerPotsdam University Dr. Robert TrumbullGFZ Potsdam Prof. Dr. Roland OberhänsliPotsdam University Prof. Dr. Monica López de LuchiBuenos Aires University (ARG)Prof. Dr. Pablo CaffeJujuy National University (ARG)Raúl Becchio, Ph.D.Salta National University (ARG)

163-G 3.4

Anonymous — Fri, 25 Sep 2015 10:15:35 +0000

10|2018 – 09|2021

Testing long-term controls of sedimentary basin architecture in the broken foreland II

M.Sc. Michele VallatiUniversity of Potsdam Prof. Dr. Maria MuttiPotsdam University

Disparate and diachronous basin stratigraphies control petroleum prospects for both conventional and unconventional resources.. The spatial variability of the strata and associated depositional geometries exert a fundamental control on the migration of fluids and determine if hydrocarbons are trapped close to the area where they were generated.

In the first phase of this project, our team has focused on understanding basin-scale controls over the complex spatial distribution of depositional facies in the postrift basin in NW Argentina. The multi-scale stratigraphic architecture reflects the interplay of extrinsic and intrinsic processes, ranging from inherited topography, tectonics, climate and sediment supply and resulted in the superposition at different temporal scales of clastics and carbonates sedimentary facies.

We now plan to focus on quantitative outcrop studies over two comparative basins to better constrain the rules determining the interplay of clastic and carbonate sedimentation. Which roles play the different controls on the basin stratigraphic evolution? How do clastics and carbonates reflect climatic processes? The diverse depositional realms provide archives of the dominant climate dynamics. Carbonate deposition is the product of biogechemical processes induced by increased alkalinity and salinity in the shallow water setting. Do the characterisation and quantification of sedimentary 3D facies distribution in outcrops provide reliable analogues for exploration, at both reservoir and regional scales?

10|2015 – 09|2018

Testing long-term controls of sedimentary basin architecture in the broken foreland

The spatial architecture of sedimentary facies in a basin exert a fundamental control over the patterns of fluid flow and determines the regional distribution of possible reservoirs and seal units. The distribution of sedimentary facies can be predicted to some extent by sequence stratigraphic theories. These models offer a conceptual framework to extrapolate facies distribution at a regional scale in 2D, ranging from continental to basinal. However, as soon the scale of observation increases, these models are not able to represent the geological complexity and facies variability in a realistic way. Furthermore, these concepts are rarely applied in 3D. Field studies reveal much more complex facies mosaics and patterns than predicted by 2D-models. Here, we will characterize the 3D facies distribution and sedimentary architecture evolution of a post-rift basin at different temporal and spatial scales prior to its evolution as a foreland basin. More specifically, the goal is to model the above mentioned parameters by coupling integrative seismic data, petrographic investigations of well logs, and outcropping sedimentary successions. Specific attention will be given to sedimentary discontinuities that often point to noteworthy events or record significant modifications of the environmental conditions, but also have the potential to affect fluid flow behavior and to compartmentalize reservoirs. Petrographic and geochemical analyses will be used to identify environmental parameters and assess diagenetic overprint in various limestone intervals. The outstanding quality of the sedimentary successions of several subbasins of the Salta Group (Yacoraite Formation) in NE Argentina offers a fantastic natural laboratory to study spatial facies variability in a postrift basin. The integration of facies analysis and stratigraphic units together with petrographic and geochemical studies on their bounding unconformities will provide data to test the role of extrinsic and autocyclic controls (tectonic, climate and sediment supply, inherited topography) on the stratigraphic successions. Constrained by stratigraphic and sedimentological information from field, well-log, and seismic data, numerical forward modeling will provide a valuable tool for testing stratigraphic correlations and the geological hypotheses controlling their occurrence. We will employ numerical modeling (DIONISOS, Petrel) to explore hypotheses concerning their occurrence and spatial distribution. This project will thus contribute to characterizing and quantifying sedimentary 3D facies distribution in outcrops (analogs for subsurface exploration) at basin and reservoir scales and to evaluate controls over their vertical and lateral stratigraphic architecture.

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

M.Sc. Wera SchmidtPotsdam University Prof. Dr. Maria MuttiPotsdam University Prof. Dr. Claudia GalliJujuy National University (ARG)

163-G 3.3

Anonymous — Fri, 25 Sep 2015 10:14:50 +0000

10|2018 – 09|2021

Lithospheric-scale 3D configuration of the Central Andes and adjacent forelands: constraints on along- and across-strike variations of density, temperature and strength

Lic. Constanza Rodriguez PicedaGFZ Potsdam Dr. Judith Bott (née Sippel)GFZ Potsdam Prof. Dr. Magdalena Scheck-WenderothGFZ Potsdam Prof. Dr. Claudia PrezziBuenos Aires University

There is a great variability in observed crustal deformation style and intensity from the subduction trench across the highest Andes to the foreland lows as well as from the Northern to the Southern Central Andes. Beside the subducting plate that exerts important controls on deformation through its (spatially and temporally) varying dynamics, it is the intrinsic physical properties of the overriding plate that govern the formation of zones of crustal strength and weakness. With this project we want to explore the present-day compositional, thermal and rheological configuration of the Central Andes and adjacent forelands on a lithospheric scale by means of data-driven 3D numerical models. While in the first project phase of StRATEGy this work package focused on the Northern Central Andes, this follow-up project will investigate lithological and related physical heterogeneities of the sediments, the crystalline crust, and the mantle of the Southern Central Andes. For this purpose, geological and geophysical observations such as seismic, seismological, gravity and thermal data will be integrated into consistent 3D models. These static models will be useful to constrain numerical thermo-mechanical experiments (such as planned in project G 3.2) that explore the stress-and-strain relationships across the entire subduction system.

10|2015 – 09|2018

3D lithosphere-scale density and thermal structure of the Central Andean foreland basins

Since the late Oligocene, the intracontinental Chaco-Paraná basin system evolved contemporaneously with the adjacent Andean fold-and-thrust belt. Consequently, four characteristic foreland depozones with different sediment thickness have developed, including (from west to east) wedge-top, foredeep, forebulge, and backbulge depositional environments. In places, very young sedimentary sequences directly overlie basement rocks in the E, while toward the orogen, they cover several kilometres of Paleozoic and Mesozoic sediments. Geophysical data provides local information on the depth to the Moho and the lithosphere-asthenosphere-boundary (LAB); accordingly, the crust and lithosphere thin from ~43 km and ~120 km in the north-eastern parts of the Chaco-Paraná basin to ~35 km and ~80 km, respectively, in the central parts. Towards the Andean orogen in the west, crustal thicknesses increase to more than 60 km and the LAB deepens to more than 150 km. Despite the abundance of geological and geophysical data, there is currently no regionally consistent 3-dimensional representation of the entire lithosphere in the region. Such a model depicting the main compositional heterogeneities of the sediments, the crystalline basement, and the lithospheric mantle has recently been developed for the Central Andes and will be critical for unraveling the long-term evolution of the foreland basin. Based on geological maps, well-logs, and seismic data made available to StRATEGy from industry and our Argentine partner E. Rossello, regional thickness variations of main tectonostratigraphic units will be integrated in a 3D structural model in the framework of PhD project. Subsidence rates and spatiotemporal shifts of depocentres will be cast in terms of phases of increased Andean tectonic loading. The models developed in this project will provide boundary conditions for petroleum-potential assessment in project [G 3.1] and a regional tectonic framework for project [G 3.4]. Furthermore, these models will allow rheological heterogeneities to be distinguished, particularly crustal zones of mechanical weakness, representing important constraints for large-scale numerical thermo-mechanical models developed in projects [G 3.2].

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

Intermediate

Dr. Christian MeeßenGFZ Potsdam Dr. Judith Bott (née Sippel)GFZ Potsdam Prof. Dr. Magdalena Scheck-WenderothGFZ Potsdam Prof. Dr. Claudia PrezziBuenos Aires University

163-G 3.2

Anonymous — Fri, 25 Sep 2015 10:14:10 +0000

10|2018 – 09|2021

The nature of the North-South change of the magnitude of tectonic shortening in Central Andes at Altiplano-Puna latitudes: a thermomechanical modeling approach

Prof. Dr. Stephan SobolevGFZ Potsdam Dr. Andrey BabeykoGFZ Potsdam Prof. Dr. Laura GiambiagiCuyo National University (ARG)M.Sc. Michaël PonsGFZ Potsdam

The first order features of the Central Andes tectonics are change of tectonic styles and magnitude of tectonic shortening from Altiplano to Puna latitudes. While causes of the change of tectonic styles were successfully investigated by comprehensive thermomechanical modeling in the first phase of the [G 3.2] StRATEGy project, the cause of change of shortening magnitude remains poorly understood. Our working hypothesis is that difference in strength of the upper plate that caused difference in tectonic styles also resulted in different rates of trench roll-back. To test this hypothesis and investigate other possibilities, in the new phase of the project we intend to extend our current models to the west including subducting Nazca plate. This will require more than doubling of the modeling area. We will build our models using experience of the first project phase and as previously will first run high-resolution 2D models along the Altiplano and Puna cross-sections and finally full 3D model including the entire region. To do that we will incorporate the updated versions of 3D thermomechanical codes LAMEM and ASPECT and 3D model of the lithospheric structure in the Central Andes developed in the partner project [G 3.3] and its extension.

10|2015 – 09|2018

Controls of Cenozoic foreland-deformation patterns

The Andean foreland demonstrates a pronounced N-S oriented differentiation in the style and magnitude of deformation and the nature of sedimentary basins. East of the Altiplano-Puna plateau and the Eastern Cordillera, a wedge-shaped, ~250-km-wide thin-skinned fold-and-thrust belt defines the eastern border of the orogen, which then transitions into the contiguous Chaco-Paraná foredeep. The spatial extent of the fold-and-thrust belt in Bolivia correlates with thick Paleozoic units, in which a series of Silurian, Devonian, and Carboniferous detachments define the basal decollément of the orogenic wedge. However, south of approximately 24°S, these mechanically weak layers thin and eventually disappear, and the thin-skinned style of deformation is replaced by the thick-skinned deformation of Santa Barbara and Sierras Pampeanas broken forelands. The gradual increase of the wavelength of foreland structures from north to south is accompanied by a decrease in accumulated shortening, a decrease in the width of orogenic plateau, and increasing lithospheric temperature. North-south trends are also evident in other key aspects of the South Central Andes, such as the N-S directed passage of Juán Fernandez Ridge during last 26 Ma and the widening of the magmatic arc and the start of an ignimbrite flare-up in the Puna. These observations suggest intimate relationships between style and intensity of deformation involving both shallow and deep lithospheric structures and processes. Supported by the results of numerous field observations, large-scale numerical thermomechanical modeling provides a valuable tool for testing geological and geodynamical hypotheses that are built on the apparent correlations between the different phenomena observed in the Central Andes. Previous 2D-models of the Central Andes already attempted to quantify some of these correlations. Recent progress in numerical modeling techniques, however, allows for an extension of this research towards 2.5- and 3D-lithospheric models. We will study the Andes from ca. 18 to 35°S, integrating the characteristics of the Nazca plate and the Andean foreland. Our numerical modeling will incorporate spatially varying age and geometry of the Nazca plate and thickness of the overriding South American plate to better constrain interplate stress transfer. Both deep and shallow model geometries and structures will be constrained by new data gathered in the framework of this initiative. Our project is tightly coupled with two other modeling projects: [G 3.3] on the 3D structural and thermal reconstruction of the evolution of the Chaco-Paraná Basin. The two projects, which cover somewhat different scales and/or locations, will exchange their input data and results, thus providing valuable constraints for each individual effort. Other important regional constraints are expected from field-studies planned in project [G 3.4], aimed at revealing long-term controls of sedimentary basin architecture in the brokenforeland realm.

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

Dr. Sibiao LiuGFZ Potsdam Prof. Dr. Stephan SobolevGFZ Potsdam Dr. Andrey BabeykoGFZ Potsdam Dr. Javier QuinterosGFZ Potsdam apl. Prof. Dr. Frank KrügerPotsdam University Dr. José MescuaMendoza University Prof. Dr. Laura GiambiagiCuyo National University (ARG)

163-G 3.1

Anonymous — Fri, 25 Sep 2015 10:13:20 +0000

10|2018 – 09|2021

Quantification of Central Andes growth and erosion in relation to sedimentation in the Neuquén and Colorado basins - a source-to-sink approach

Lic. Román FealGFZ Potsdam Dr. Robert OndrakGFZ Potsdam Prof. Dr. Matias GhiglioneBuenos Aires University (ARG)Prof. Dr. Laura GiambiagiCuyo National University (ARG)Prof. Manfred Strecker, Ph.D.Potsdam University

This project follows a source to sink approach relating Central Andes growth with sedimentation in Neuquén and Colorado basins. The working hypothesis is that tectonic mountain growth produces large volumes of eroded rocks and subsidence in the foreland basins that catches those sediments. While contractional tectonics accelerates subsidence rates of foreland basins, periods of neutral tectonics produce low to no accommodation space in the retroarc. On those cases, large portion of sediments will bypass the continent toward the offshore basins, therefore controlling overburden and petroleum generation. The idea is to compare the Central Andes (34°-42°SL) changing tectonics and exhumation rates - source region - with sedimentation rates and volumes of sediments in the Neuquén foreland basin to determine if there is an inverse correlation to the Colorado offshore basin - sink basins - for periods to be defined during data acquisition. In particular, we will test the hypothesis by calculating sedimentation rates in the Colorado offshore basin from available basin models. Sedimentation rates in the Neuquén basin and tectonic and exhumation in the Central Andes can be summarized from a plethora of publicly available data. We will study paradigmatic localities in the Neuquén basin to recognize the appearance of highly condensed stratigraphic sections representing periods of neutral tectonics. Lab analysis will be conducted in order to better constrain and characterize those periods of potential sediment bypass towards the offshore which is of significance for the evolution of the petroleum potential of the region. The project will also contribute to the partner projects [G 3.2] and [G 3.3] by providing data from the sedimentary cover of the region.

10|2015 – 09|2018

Tectono-stratigraphic evolution of the intermontane Salta basin and Chaco-Paraná foreland basin: characterization and evolution of petroleum potential

The evolution of the inter-mountain Salta basin is related to the evolution of the Central Andes. An intracontinental rift was formed by extensional processes and subsequently filled by up to 5500 m sediments from the Neocomian to the Paleogene intercalated by minor volumes of magmatic rocks. This complex constitutes the Salta group. Paleoenvironmental analysis reveals depositional history controlled by tectonic and climatic changes. Deformation of the basin began at the end of the Eocene and resulted in a rapid transition from a rift basin to a foreland basin filled by synorogenic continental deposits. The Chaco-Paraná Basin comprises the undeformed Chaco-Parana plain to the east, and the Subandes, Sierras Pampeanas, and the ranges of the Santa Barbara System to the west. The basin comprises >10 km of sediments spanning the Silurian to the Present. It is asymmetric, with a total stratigraphic thickness of Cenozoic rocks >7.5 km deposited at the western margin that thin eastward. Deformation of the Subandes and the Salta Basin developed since the Eo-Oligocene; and is characterized mainly by in-sequence, thin-skinned thrusting that includes ramp anticlines and passive roof duplexes separated by thrust faults and synclines, although Plio-Pleistocene out-offsequence thrusting has also been reported. The Subandes are home to several major gas discoveries during the last 20 years. The Chaco-Paraná foreland basin, as a frontier exploration area, has a high resource potential (some assessments attribute almost one third of Argentina’s total unconventional hydrocarbon potential to this basin), although exploration concepts are largely unproven. By combining 3D petroleum system modeling techniques with detailed source rock and petroleum-accumulation information, volumetric assessments of petroleum potential can be produced at different scales for basin wide assessments of the possible resource potential. We plan to investigate the evolution of the inter-mountain Salta basin and the Chaco-Parana Basin to deconvoluting its burial and thermal histories as well as source rock maturation, petroleum generation, migration, accumulation and leakage. A detailed basin modeling study is planned which integrates the tectono-stratigraphic evolution, timing of major unconformities, spatiotemporal migration of depocenters, source-rock occurrence and type to elucidate the hydrocarbon generation and migration history of this basin. Special focus will be put on the climatic and tectonic processes operating in the sediment source areas to determine the main variables and forcing conditions controlling the stratigraphic architecture and the distribution of source rocks. Within this context including all information available on the crustal evolution of the NW of Argentina is a pre-requisite. Especially the buildup of the Andes, and fault reactivation and thrusting along the basin margins are important factors in controlling both the burial as well as the maturation and petroleum migration histories. This project will provide an integrated and concise description of the evolution of Salta and Chaco-Parana basin petroleum systems. The project will cooperate closely with projects [G 3.3] and [G 3.4] to define boundary conditions for basin modeling and detailed description of the tectono-stratigraphic and sedimentary evolution of the basin.

Working Package:

WP3 - Basin Modeling

Temporal Process:

Long Term

Intermediate

Dr. Ricardo Ruiz MonroyGFZ Potsdam Dr. Robert OndrakGFZ Potsdam Prof. Dr. Magdalena Scheck-WenderothGFZ Potsdam Prof. Dr. Eduardo RosselloBuenos Aires University (ARG)Prof. Dr. Brian HorsfieldGFZ Potsdam

163-G 2.3

Anonymous — Fri, 25 Sep 2015 10:12:05 +0000

10|2018 – 09|2021

Depositional and exhumation history of the Cretaceous Lomas de Olmedo rift basin

M.Sc. Willemijn van KootenPotsdam University apl. Prof. Edward Sobel, Ph.D.Potsdam University Dr. Cecilia Del PapaCórdoba University (ARG)Dr. Alejandro BandeTectpetrol S.A. Buenos Aires (ARG)Dr. Daniel StarckTecpetrol A.S. Buenos Aires (ARG)Prof. Dr. Patricio PayrolaSalta University (ARG)

The Salta Rift in NW Argentina is an intracontinental rift with thick syn- and post-rift deposits that have been extensively explored for petroleum. The Lomas de Olmedo and the Tres Cruces sub-basins are E-W and N-S trending portions of the rift, respectively. The majority of the former sub-basin lies in the subsurface, to the east. The transition zone between these rift segments outcrops ~20 km east of Humahuaca, where the thick Cianzo syncline provides stunning exposures of the entire syn- and post-rift section. The Hornocal fault bounds the syncline and formed the northern margin of the rift. Published structural mapping and unpublished apatite fission track data show that the Cretaceous Hornocal normal fault has been inverted in the Miocene. There are prominent angular unconformities in the syncline that separate syn- and post-rift strata; these appear to delineate growth strata associated with the fault. Therefore, this locality provides an excellent opportunity to study proximal rift-margin sedimentary deposits as well as to study the exhumation history of the adjacent rift shoulder. We plan to conduct zircon (U-Th)/He thermochronology to constrain the Cretaceous exhumation of the rift shoulder. We will also examine post-rift, Cenozoic reactivation of structures using apatite fission track thermochronology. In the basin, the syn-rift sequence reportedly contains carbonate nodule-bearing paleosols. We will analyze these using both stable isotopes for paleoclimate analysis and U/Pb dating for age control. Stratigraphic, sedimentologic, provenance, and structural studies will characterize the basin fill. We plan to examine along-strike variations of rift shoulder exhumation with the aid of subsurface data from the Lomas del Olmedo sub-basin to the east.

10|2015 – 09|2018

The influence of inherited extensional structures on the growth of basement-cored ranges and their foreland basins

The reactivation of pre-existing normal faults during subsequent contractile deformation can exert a profound influence on both exhumation of ranges and sedimentary basin formation. This topic has been addressed in the well-exposed, arid intermontane basins and ranges of NW Argentina as well as more humid sectors of the broken foreland farther east. However, the more humid eastern flank of the Sierras Pampeanas has been less well-studied, despite its simpler structural history. In the Tucumán and Choromoro basins, structures that deform the foreland basins as well as their sedimentary thicknesses have been well analyzed using industry seismic reflection data. However, to date, a quantitative source-to-sink approach has not been applied in this area. Therefore, we will integrate thermochronology, structural data, and provenance and basin analysis to test whether Cretaceous normal faults exert a first-order control on the pattern and magnitude of Cenozoic contractile deformation in basement-cored ranges as well as subsidence patterns in the adjacent foreland basins. The ages of the largely continental foreland-basin fill remain imprecisely constrained, with the exception of the strata corresponding to the Middle Miocene Paraná marine transgression, reflecting both the difficulty of dating non-marine sequences and the poor outcrop quality. To address this problem, we will constrain depositional ages by dating interbedded volcanic ashes using either zircon U/Pb or 40Ar/39Ar dating. Furthermore, we will collect sandstone samples for detrital zircon geochronology using LA-ICP-MS to provide maximum depositional ages. Together, this approach will enable us to derive realistic models of flexural basin subsidence, especially in the vicinity of spatially disparate basement uplifts. Reconstructions of range exhumation and sediment deposition will be accomplished by using apatite fission-track dating on detrital sandstones to determine changes in lag time. Where possible, we will conduct double dating (fission track and U/Pb) to better constrain a local versus distal source for these sediments. We will also extend the database of basement thermochronologic data in Sierra Aconquija and the Cumbres Calchaquies to evaluate the timing and magnitude of exhumation of both Cretaceous and Cenozoic structures. These two ranges are along strike from each other and bound the Tucumán and Choromoro basins, respectively used thermochronology to delineate the extent of Cretaceous rift structures within these ranges. As the Sierra Aconquija was strongly exhumed in the Neogene while the Cumbres Calchaquíes were primarily exhumed during the Cretaceous, this region provides an ideal setting to examine the influence of pre-existing normal faults on Cenozoic evolution.

Working Package:

WP2 - Tectonics

Temporal Process:

Long Term

Dr. Sebastian Zapata HenaoPotsdam University apl. Prof. Edward Sobel, Ph.D.Potsdam University Dr. Cecilia Del PapaCórdoba University (ARG)

163-G 1.4

Anonymous — Fri, 25 Sep 2015 10:10:18 +0000

10|2018 – 09|2021

Sources and transformation of organic carbon in the fold and thrust belt of the NW Argentinian pre-cordillera

M.Sc. Sophia DoschGFZ Potsdam Dr. Dirk SachseGFZ Potsdam Prof. Dr. Niels HoviusGFZ Potsdam Dr. Luis PalazzesiNational Museum of Sciences (ARG)Dr. Ricardo SzupianyNational University of the Littoral (ARG)Dr. Francisco LatosinskiNational University of the Littoral (ARG)

Organic carbon mobilized from soils (biospheric carbon) as well as from sedimentary rocks (petrogenic carbon) in orogenic ranges is now being recognized as a major component of the Earth’s carbon cycle. Long-term burial of modern biospheric carbon in oceanic sinks results in a removal of CO₂from the atmosphere, whereas oxidation of petrogenic carbon would add CO₂ to the atmosphere, hence impacting the long-term evolution of climate. However, our understanding of the processes controlling mobilization and potential oxidation of this carbon during transport, redeposition and remobilization downstream is limited, preventing a quantitative assessment of organic carbon fluxes and their changes over time.

We aim to understand sources and transformation of organic carbon originating from the NW Argentinian foothills of the Andes and deposited in the fold and thrust belt over various geological timescales. Fingerprinting the organic material using organic-geochemical, stable and radiogenic isotope-based approaches, we investigate organic carbon in modern soils, intramontane sedimentary basins and modern rivers draining the Andes along steep climatological gradients. Using these tools we aim to identify the tectonic and climatic drivers and estimate organic carbon fluxes and assess their importance on longer geological timescales.

10|2016 - 09|2019

Climatic, biotic and geomorphic drivers of the isotopic composition of terrestrial organic matter transported through fluvial systems draining the NW Argentinian Andes

The key question which this project aims to answer is how tectonic processes such as mountain-range uplift affect atmospheric circulation patterns and enforce subsequent hydrological changes. The NW Argentine Andes are an ideal location to study these processes, due to unique and characteristic circulations patterns associated with the South American Low Level Jet (SALLJ) as part of the SAMS, which were established as a consequence of the topographic growth of the Andean orogen. Based on our previous studies, the imprint of these circulation patterns on modern stable water-isotope ratios is reasonably well understood. Here, we plan to conduct catchment investigations to understand and provide a sound base to decipher the development of such tectonically forced hydrological patterns during the geological past. In particular, we will study terrestrial climate archives in the intermontane basins along and across the NW Argentine Andes representing different episodes of range uplift and orographic-barrier formation during the last 10 Ma. As a paleohydrological proxy, we will employ the hydrogen stable isotope composition of leaf wax lipids (δDwax), which has been shown to record the δD values of meteoric plant-source water as well as terrestrial evapotranspiration, to identify changes in moisture source area (i.e. before and after the establishment of the SALLJ), and to record the onset of aridity in the basins of the orogen interior. In addition, the stable carbon-isotope composition of these compounds (δ¹³C_wax) will be analyzed to assess changes in vegetation cover from C3 to aridity adapted C4 plants. By taking this approach into the spatial domain, i.e. using multiple terrestrial archives from different basins along (N-S) and across (E-W) the Andes, we will identify past dynamics of atmospheric processes and asses these changes in the context of mountain-range uplift. The PhD candidate will focus on understanding the isotopic characteristics of leaf waxes and their climatic and biotic (i.e. vegetation distribution) drivers in modern catchments. By studying the modern hydrological gradient across (E-W) and along (N-S) the orogen and its imprint on leaf-wax stable isotope ratios, we will develop a sound base to apply this proxy on a variety of terrestrial climate archives from the last 10 Ma.

Working Package:

WP1 - Climate

Temporal Process:

Long Term

Dr. Marisa RepaschGFZ Potsdam Dr. Dirk SachseGFZ Potsdam Prof. Dr. Achim BrauerGFZ Potsdam Dr. Luis PalazzesiNational Museum of Sciences (ARG)

WP(3): Basin Modeling

Anonymous — Fri, 25 Sep 2015 09:56:09 +0000

The Andes exhibit first-order, along-strike variations in morphotectonic provinces, width, and deformation style. Allmendinger and Gubbels (1996) have suggested that the shortening style of the whole system might be controlled by the north-to-south variations in the lithospheric mechanical properties, which are sensitive to temperature and lithology. This inference was subsequently confirmed by thermo-mechanical modeling¹, emphasizing how mechanical weakening and failure of the foreland sedimentary cover drastically affect the rate and style of tectonic deformation and explain extensive understhrusting of the foreland in the Subandes. It is not known if these processes are promoted by increased rainfall or sedimentation rates, but in this context, it has been suggested that hydrocarbon maturation may have influenced the onset of the thin-skinned tectonics in the Subandes².

Other decisive factors in the location and evolution of sedimentary basins in the Andean realm include co-varying changes in magmatism and the geometry of the subducting slab³. Variations in the latter lead to horizontal translation of the ~100-km-deep zone of slab dehydration and mantle-wedge melting⁴ and/or frontal tectonic erosion, which can also account for migration of the arc towards the foreland⁵. Slab flattening has been attributed to changes in buoyancy due to subduction of oceanic crust thickened by aseismic ridges⁶. A diagnostic feature of this process might be the occurrence of a foreland-ward shift in magmatic activity culminating with a magmatic lull. Basement faulting in the foreland, far from the plate boundary, may also occur, although its diagnostic value is disputed. The oblique subduction of the Nazca plate and the Juán Fernandez Ridge, may thus have led to a spatiotemporal migration of deformation, uplift, and basin formation. However, this scenario has never been fully tested. Additional aspects, such as the thermo-mechanical evolution of the subduction zone and associated dehydration processes in different segments with variable subduction angles may fundamentally impact upper-plate deformation, magma formation and emplacement (with implications for metallogenesis, see WP4), variations in the temperature field of the foreland basin, and thus the generation of hydrocarbons. Collectively, all these issues are well represented by the different evolutionary stages of the hydrocarbon-bearing Chaco-Paraná basin in NW Argentina and SE Bolivia.

The Chaco-Paraná Basin has been developing since the Eo-Oligocene; it comprises the undeformed Chaco-Parana plain to the east, and the Subandes, Sierras Pampeanas, and the ranges of the Santa Barbara System to the west. Crustal thicknesses of 42 km and 32-35 km have been inferred for the eastern Paraná and Chaco basins, respectively. Because of a highvelocity upper-mantle lid and a lack of a resolvable low-velocity zone (at least down to 200 km), the Paraná Basin has been regarded as “cratonic” in character⁷. In the Chaco Basin, on the contrary, upper-mantle S-wave velocities are low, indicating an “asthenospheric” character. In line with this, S receiver function analysis suggests a shallowing of the lithosphere-asthenosphere boundary from ~120 km in the NE Chaco-Paraná Basin to ~80 km in the central Chaco-Paraná Basin⁸. A W-to-E transect across the foreland reveals four juxtaposed depozones that can be distinguished based on sediment-fill geometries, average elevation, and Bouguer gravity anomalies. These zones include (1) the 1- to 3-km thick Cenozoic deposits in the Subandes, (2) a 3- to 4-km thick foredeep prism that tapers toward the eastern Chaco Plain, (3) a thin veneer of Quaternary alluvium forming the forebulge, and (4) a thin (0.5 km) accumulation of sediment in the back-bulge zone.

The Chaco-Paraná basin comprises >10 km of sediments spanning the Silurian to the Present. It is asymmetric, with a total stratigraphic thickness of Cenozoic rocks >7.5 km deposited at the western margin⁹ that thin eastward. The Subandes of the Chaco-Paraná foreland basin are characterized by mainly in-sequence, thin-skinned thrusting that includes ramp anticlines and passive roof duplexes^10,11 separated by thrust faults and synclines, although Plio-Pleistocene out-of-sequence thrusting has also been reported¹². The main decollement dips ~3°W and involves Silurian shales¹³. Intermediate detachment levels in Devonian shales generate lift-off structures and decoupling of the lower and upper structural levels¹⁴. Estimated total shortening in the Subandes is between 67 and 100 km^15,16.

The Subandes are home to several major gas discoveries during the last 20 years. Basin-wide assessments of resource potential are based on a variety of techniques. Production/analogue based assessments¹⁷ use existing or analogue based production-rate curves to estimate ultimate recoverable resources. Volumetric or in-place methods¹⁸ use available data on source-rock quality, type, extent, and maturity to derive estimates of potential volumes of undiscovered petroleum resources. By combining 3D petroleum system modeling techniques with detailed source rock and petroleum-accumulation information, volumetric assessments of petroleum potential can be produced at different scales. Recent publications on basin-wide generated, migrated, accumulated, and lost petroleum masses show how dynamic basin evolution is linked to the present-day resource potential¹⁹, for both conventional and unconventional petroleum resources.

Temporal Process:

Long Term

Work Package:

WP3 - Basin Modeling

Bibliography:

¹ Babeyko et al., 2006; ² Babeyko and Sobolev, 2005; ³ Jordan et al., 1983; ⁴ Folguera et al., 2001; ⁵ Kay et al., 2005; ⁶ e.g. Gutscher et al., 1999; ⁷ Snoke and James. 1997; ⁸ Heit et al., 2007; ⁹ Uba et al., 2005; ¹⁰ Kley et al., 1999; ¹¹ McQuarrie, 2002; ¹² Uba et al., 2009; ¹³ Kley et al., 1999; ¹⁴ Hernándes and Echavarria, 2009; ¹⁵McQuarrie, 2002; ¹⁶ Barke and Lamb, 2006; ¹⁷ Charpentier and Cook, 2012; ¹⁸ White and Gehman, 1979; ¹⁹ Berbesi et al., 2012

WP(2): Interplay between tectonics & inherited crustal inhomogeneities

Anonymous — Fri, 25 Sep 2015 09:54:40 +0000

The region east of the 6000 m high Puna plateau and the Eastern Cordillera of NW Argentina is characeterized by a wedge-shaped ~250-km-wide fold-and-thrust belt, which defines the eastern border of the orogen and transitions into the unrestricted Chaco-Paraná foredeep. The spatial extent of the fold-and-thrust belt correlates with thick Paleozoic units that provide the basal decollement of the wedge¹. South of 24°S, however, these mechanically weak layers thin out and disappear, and the thinskinned style of deformation terminates^2,3. Instead, normal faults and transfer structures of the Cretaceous Salta Rift or Paleozoic metamorphic fabrics have accommodated shortening during the Cenozoic^4-9. The reactivated, inherited anisotropies have produced discrete ranges that occur both along the eastern flank of the plateau and far to the east within the otherwise undeformed foreland¹⁰. Virtually all of the ranges in the so-called “broken foreland” of the Sierras Pampeanas and the Santa Barbara System are bounded by faults that have been active during the Cenozoic, but range uplifts have been highly disparate in time and space, and there is no clear deformation front as in the foreland fold-and-thrust belt to the north. The gradual increase in the wavelength of foreland structures from north to south is accompanied by decreasing amounts of shortening and plateau width, but increasing lithospheric temperatures, suggesting a close relationship between structural inheritance and the style and intensity of deformation, even at the level of deep lithospheric structures¹¹.

At the foundation of understanding the tectonic and sedimentary processes in foreland realms lie the crucial questions of which structures may rupture, what magnitude of shaking can occur, how seismicity and climate change might affect the surface-process regime in the near future, and what aspects of the long-term geomorphic and depositional characteristics influence resource generation. While we can place bounds on the answers to the seismicity related questions in plate-boundary settings, the full array of earthquake ruptures, long-term tectonic deformation, interaction between faults, and depositional systems that may be generated in broken foreland settings may mask the desired answers, largely because we do not understand the basic processes that govern them.

These complex aspects of broken foreland regions are very well expressed in the Andean foreland. Some ranges in the broken foreland constitute large, tectonically active fault blocks^12,13 or anticlines that have formed over blind thrusts, such as the growing anticlines west of the town of Salta that were associated with a M6.3 earthquake in February, 2010¹⁴. The diachronous nature of long-term range uplift and deformation of intermontane basins is mirrored by the seemingly random occurrence of earthquakes associated with basement faults¹⁵, the manifestations of paleo-earthquakes¹⁶, and on longer timescales, the evolution of regional unconformities and disconnected depocenters. A further complication includes the potential for changes in climatic boundary conditions to influence the surface process system, particularly as the growth of orographic barriers can change atmospheric circulation and rainfall patterns. In this context, there appears to be a relationship between sediment removal and ensuing changes in crustal stresses along the E flank of the Central Andes¹⁷. Potential fault reactivation resulting from associated stress changes within and along basin margins may follow the removal of the sedimentary load, further complicating the evolution of foreland deformation, subsidence patterns, sediment transport, and ultimately, the representation of orogenic processes in the foreland stratigraphic records. Such complex relationships have not been elucidated by coupling landscape evolution and large-scale thermo-mechanical models that would allow for a detailed 3D characterization of the present-day state of the lithosphere¹⁸.

Temporal Process:

Long Term

Work Package:

WP2 - Tectonics

Bibliography:

¹ Echavarria et al., 2003; ² Kley and Monaldi, 2002; ² Ramos et al., 2002; ⁴ Grier et al., 1991; ⁵ Kley and Monaldi, 2002; ⁶ Kley et al., 2005; ⁷ Carrera et al., 2006; ⁸ Hongn et al., 2007; ⁹ Hain et al., 2011; ¹⁰ Mon and Salfity, 1995; ¹¹ Babeyko and Sobolev, 2005; ¹² Meigs and Nabelek, 2010; ¹³ Costa and Vita-Finzi, 1996; ¹⁴ LINK: http://earthquake.usgs.gov/earthquakes/dyfi/events/us/2010tfc3/us/; ¹⁵ Alvarado and Beck, 2006; ¹⁶ Costa and Vita-Finzi, 1996; ¹⁷ Pingel et al., 2013 ; ¹⁸ Scheck-Wenderoth and Maystrenko, 2008