Dynamic of a lacustrine sedimentary system during late rifting at the Cretaceous‐Palaeocene transition: Example of the Yacoraite Formation, Salta Basin, Argentina

The architecture of lacustrine systems is the result of the complex interaction between tectonics, climate and environmental parameters, and constitute the main forcing parameters on the lake dynamics. Field analogue studies have been performed to better assess such interactions, and their impact on the facies distribution and the stratigraphic architecture of lacustrine systems. The Yacoraite Formation (Late Cretaceous/Early Palaeocene), deposited during the sag phase of the Salta rift basin in Argentina, is exposed in world-class outcrops that allowed the dynamics of this lacustrine system to be studied through facies analysis and stratigraphic evolution. On the scale of the Alemania-Met\ue1n-El Rey Basin, the Yacoraite Formation is organized with a siliciclastic-dominated margin to the west, and a carbonate-dominated margin to the east. The Yacoraite can be subdivided into four main \u2018mid-term\u2019 sequences and further subdivided into \u2018short-term\u2019 sequences recording high frequency climate fluctuations. Furthermore, the depositional profiles and identified system tracts have been grouped into two end-members at basin scale: (a) a balanced \u2018perennial\u2019 depositional system for the lower part of the Yacoraite Formation and (b) a highly alternating \u2018ephemeral\u2019 depositional system for the upper part of the Yacoraite Formation. The transition from a perennial system to an ephemeral system indicates a change in the sedimentary dynamics of the basin, which was probably linked with the Cretaceous/Tertiary boundary that induced a temporary shutdown of carbonate production and an increase in siliciclastic supply

Tectono-sedimentary evolution of the Plio-Pleistocene Corinth rift, Greece

The onshore central Corinth rift contains a syn-rift succession >3 km thick deposited in 5–15 km-wide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake-margin conditions and finally to sub-lacustrine turbidite channel and lobe complexes, and deep-water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development – Rift 1 from 5.0–3.6 to 2.2–1.8 Ma and Rift 2 from 2.2–1.8 Ma to present. Rift 1 developed as a 30 km-wide zone of distributed normal faulting. The lake was fed by four major N- to NE-flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from >1000 m to present-day sea level. The growth, linkage and death of normal faults during the two phases of rifting is interpreted to reflect self-organisation and strain localisation along co-linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike-slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at c. 400–600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt

Catchment drainage network scaling laws found experimentally in overland flow morphologies

The scaling relation between the drainage area and stream length (Hack's law), along with exceedance probabilities of drainage area, discharge, and upstream flow network length, is well known for channelized fluvial regions. We report here on a laboratory experiment on an eroding unconsolidated sediment for which no channeling occurred. Laser scanning was used to capture the morphological evolution of the sediment. High-intensity, spatially nonuniform rainfall ensured that the morphology changed substantially over the 16-hr experiment. Based on the surface scans and precipitation distribution, overland flow was estimated with the D8 algorithm, which outputs a flow network that was analyzed statistically. The above-mentioned scaling and exceedance probability relationships for this overland flow network are the same as those found for large-scale catchments and for laboratory experiments with observable channels. In addition, the scaling laws were temporally invariant, even though the network dynamically changed over the course of experiment

Rapid spatiotemporal variations in rift structure during development of the Corinth Rift, central Greece

The Corinth Rift, central Greece, enables analysis of early rift development as it is young (<5Ma) and highly active and its full history is recorded at high resolution by sedimentary systems. A complete compilation of marine geophysical data, complemented by onshore data, is used to develop a high-resolution chronostratigraphy and detailed fault history for the offshore Corinth Rift, integrating interpretations and reconciling previous discrepancies. Rift migration and localization of deformation have been significant within the rift since inception. Over the last circa 2Myr the rift transitioned from a spatially complex rift to a uniform asymmetric rift, but this transition did not occur synchronously along strike. Isochore maps at circa 100kyr intervals illustrate a change in fault polarity within the short interval circa 620-340ka, characterized by progressive transfer of activity from major south dipping faults to north dipping faults and southward migration of discrete depocenters at ~30m/kyr. Since circa 340ka there has been localization and linkage of the dominant north dipping border fault system along the southern rift margin, demonstrated by lateral growth of discrete depocenters at ~40m/kyr. A single central depocenter formed by circa 130ka, indicating full fault linkage. These results indicate that rift localization is progressive (not instantaneous) and can be synchronous once a rift border fault system is established. This study illustrates that development processes within young rifts occur at 100kyr timescales, including rapid changes in rift symmetry and growth and linkage of major rift faults

Architecture stratigraphique et flux sédimentaires sur la marge Sud du golfe de Corinthe (Grèce) : Analyse de terrain, modélisations expérimentales et numériques (Thèse soutenue le 2 février 2007)

The objective of the present work is to characterize sediment supply dynamics within the Plio-Pleistocene Corinth Rift using an integrated approach based on field observations and analyses, experimental modeling and numerical modeling. Detailed sedimentological, structural and biostratigraphical studies on the southern coast of the rift provide a tectono-stratigraphic model within a well-constrained climatic and eustatic setting. Stratigraphic simulations (DIONISOS) are used to validate this model, to quantify the sediment supply and to discuss the relative role of four controlling factors on stratigraphic architecture (sediment flux, water flux, subsidence, eustasy). Finally, a geomorphological experimental approach has been developed to study the relative role of factors (rainfall, uplift rate.....) that control sediment supply and their record within the sedimentary signal.L'objectif de ce travail est de caractériser l'évolution du flux sédimentaire sur la marge sud du golfe de Corinthe, avec un aller-retour entre données de terrain, modélisations expérimentales et modélisations numériques. L'acquisition de données de terrain a permis d'établir l'évolution tectono-sédimentaire du rift de Corinthe dans le contexte climatique et eustatique bien contraint du Plio-Pléistocène. Les simulations numériques stratigraphiques (DIONISOS) ont ensuite permis de valider ce modèle d'évolution, de quantifier les flux sédimentaires et de discuter des facteurs de contrôle de l'architecture stratigraphique à différentes échelles de temps et d'espace. Les modélisations expérimentales ont enfin permis de discuter des facteurs de contrôle des flux sédimentaires et de leurs enregistrements dans les corps sédimentaires

Architecture stratigraphique et flux sédimentaires sur la marge sud du golfe de Corinthe (Grèce) (analyse de terrain, modélisations expérimentales et numériques)

L objectif de ce travail est de caractériser l évolution du flux sédimentaire sur la marge sud du golfe de Corinthe, avec un aller-retour entre données de terrain, modélisations expérimentales et modélisations numériques. L acquisition de données de terrain a permis d établir l évolution tectono-sédimentaire du rift de Corinthe dans le contexte climatique et eustatique bien contraint du Plio-Pléistocène. Les simulations numériques stratigraphiques (DIONISOS) ont ensuite permis de valider ce modèle d évolution, de quantifier les flux sédimentaires et de discuter des facteurs de contrôle de l architecture stratigraphique à différentes échelles de temps et d espace. Les modélisations expérimentales ont enfin permis de discuter des facteurs de contrôle des flux sédimentaires et de leurs enregistrements dans les corps sédimentaires.The objective of the present work is to characterize sediment supply dynamics within the Plio-Pleistocene Corinth Rift using an integrated approach based on field observations and analyses, experimental modeling and numerical modeling. Detailed sedimentological, structural and biostratigraphical studies on the southern coast of the rift provide a tectono-stratigraphic model within a well-constrained climatic and eustatic setting. Stratigraphic simulations (DIONISOS) are used to validate this model, to quantify the sediment supply and to discuss the relative role of four controlling factors on stratigraphic architecture (sediment flux, water flux, subsidence, eustasy). Finally, a geomorphological experimental approach has been developed to study the relative role of factors (rainfall, uplift rate.....) that control sediment supply and their record within the sedimentary signal.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

A Lacustrine Record for the Cretaceous–Paleogene Boundary—Yacoraite Fm., (Northwest Argentina)

The Yacoraite Fm. (Salta rift basin, Argentina) consists of a mixed carbonate–siliciclastic lacustrine succession, interbedded with volcanic ash layers and organised in four third-order stratigraphic sequences. It is one of the few sites in South America that encompass the Cretaceous–Paleogene (K–Pg) transition, the position of which remains debated. Here, samples were collected along a depocentral stratigraphic section that was previously dated by zircon and carbonate U-Pb geochronology. The consistency between zircon and carbonate U-Pb ages, together with an accurate petrographic analysis, allowed the selection of carbonates potentially preserving the original geochemical signature. Accordingly, C-O stable isotopes were analysed from microbialites, oncoids, ooids and lacustrine cements. The available depositional age model from zircon geochronology defined the stratigraphic interval, potentially including the K–Pg transition. Within this interval, carbonates provided negative δ13C values consistent with the negative C anomaly recorded in various K–Pg sites elsewhere. Additionally, spherical particles resembling spherulites related to meteorite impacts were found in two samples. Accordingly, the K–Pg transition could be placed at the top of the second stratigraphic sequence. These findings encourage further investigation of the Yacoraite Fm. to gain insights into the response of South American terrestrial settings to the K–Pg palaeoenvironmental crisis

Sedimentary record of tectonic and climatic erosional perturbations in an experimental coupled catchment-fan system

International audienceThis article deals with the stratigraphic record of a climatic or tectonic perturbation of an experimental coupled catchment-fan system. Following Bonnet & Crave's results (2003), which suggest that it is possible to differentiate between climatic or tectonic causes of surface uplift of an erosional topography from the record of sediment flux output, we design a new experimental device to test this proposition in the sedimentary signal. This device allows the study of a coupled erosion- sedimentation system at the laboratory scale for given and changing uplift and rainfall rates. On the basis of experimental results, we propose a methodology to study alluvial fan architecture from large-scale geometries to stacking pattern and sequence analysis. In these experiments, the erosional perturbation resulting from climate or tectonic forcing induces a typical dynamic in terms of both sediment supply and the ratio between the sediment and water supply, which controls the transport capacity. The four possible forcings (rainfall rate and uplift rate increase or decrease, respectively) then result in unique dynamics of the combined parameters such as the fan slope, apex aggradation, mean sedimentation rate, grain size distribution, bed thickness and frequency and facies stacking. We first analyse large-scale geometries (onlap, toplap, downlap or truncation) and then fine-scale sedimentological features (fining, thinning, coarsening, thickening) in order to discriminate the nature of the forcing. This conceptual model could be adapted to real world alluvial fans in order to recognize and separate the driving mechanisms from each other