The volume and grain-size of sediment supplied from catchments fundamentally control basin stratigraphy. Despite this, few studies have constrained sediment budgets and grain-size exported into an active rift and compared this to the characteristics of depositional stratigraphy. Here, we use the Gulf of Corinth as a natural laboratory to quantify the controls on sediment export within an active rift. We measured the hydraulic geometries, surface grain-sizes of channel bars and full-weighted grain-size distributions of river sediment at the mouths of multiple catchments draining the rift, which constitute 83% the Gulf’s drainage area. Results show that grain-size increases westward along the southern coast of the Gulf and that median and coarse-fraction of the sieved grain-size distribution are primarily controlled by bedrock lithology, with late Quaternary uplift rates exerting a secondary control. We also demonstrate that the median and coarse-fraction of the grain-size distribution are predominantly transported in bedload; however, typical sand-grade particles are transported as suspended load at bankfull conditions, suggesting disparate source-to-sink transit timescales for sand and gravel. Using this data, we derive both a Holocene sediment budget and a grain-size specific bedload discharged into the Gulf of Corinth using the grain-size measurements and previously published estimates of sediment fluxes and volumes. Finally, we demonstrate that at the scale of individual fault blocks, these sedimentary signals fundamentally control the nature of basin deposition, including the characteristics and architectures of hangingwall Gilbert deltas. Our results therefore highlight the importance of linking geomorphic and stratigraphic approaches in areas of active extension.

Environmental signals produced by changes in climate or tectonic regime are transferred and modified through sedimentary systems from source to sink. Sediment (and therefore signal) transfer in segmented systems is interrupted through sediment storage in e.g. lacustrine sinks. The Alpine orogen is a mountain chain characterized by high denudation rates that sources important rivers such as the Rhine river. This study focuses on the Aare river, a tributary to the Rhine, that originates in the Swiss High Alps. The course of the present-day Aare river is controlled by an overdeepened valley carved during the Pleistocene glaciations, and segmented by several lakes. We present a provenance dataset based on detrital garnet geochemistry from modern river sands, Pleistocene deposits from drill core samples and river terraces, a Pliocene river terrace, and the Miocene Molasse bedrock. We show that before the Pleistocene, i.e. before valley incision, detritus was transferred directly from the High Alps to the Rhine river plain. After the incision in the Pleistocene, the Aare river recycled the incised local Molasse bedrock. Today, the Aare river is in turn recycling those Pleistocene river terraces as well as the local bedrock. First-cycle detritus from the High Alps is instead stored in man-made and natural lakes. Our data shows that the “erosional engine” of sedimentary systems changes drastically in response to geomorphic reorganizations, and that provenance analysis is a prerequisite to locate the sediment source, as well as the origin of any environmental signal produced in that source.

Within the framework of a geoarchaeological project to reconstruct the environmental conditions in the hinterland of an archaeological excavation in Northern Lebanon a drilling core near to the Nahr-El-Jaouz river mouth was taken in 2022. The core exhibits a 10,50m thick succession of Holocene fluvial deposits. Sampling comprised more than 100 samples. Sedimentological techniques using grain size distributions and textural parameters were applied for the assessment of facies type and the conditions of sediment transport and deposition.

At a drilled depth of 10,00-10,50m gravelly sediments occurred representing the deltaic foreset followed by an alternating sequence of muds and sandy muds deposited directly at the river mouth or somewhat upstream (deltaic topset). The section above consisting of sandy to muddy sediments was formed by temporarily floods or stagnant water showing mainly suspension transport of the particles. The facial interpretation indicates a transition between a lagoonal environment of the topset and a distal floodplain far from the main river.

Most of the upper core (9,35m to the surface) shows sediments formed within a wetland environment. Frequent facial changes from distal to proximate floodplain positions with muddy and sandy deposits can be observed. Gravelly layers occur as occasional intercalations deposited by more turbulent floods of different reach and force.

The drill core indicates a former sea arm of several kilometres in length for the Nahr-El-Jaouz river mouth. Unfortunately, at present no age data from ¹⁴C analyses of taken charcoals or from OSL dating are available. These analyses are still in progress.

Hybrid beds or linked debrites are deposits that form under bi- or tri-partite flow conditions, involving transitions from turbulent to laminar flow conditions. Often, hybrid beds occur with distal or lateral flow transformation following significant entrainment of a muddy substrate and/or declining turbulent energy. Hybrid beds have been noted to make up significant proportions of deposits within basin-floor setting worldwide, most commonly within the distal fringes of lobe systems. The stratigraphic distribution of hybrid beds has been linked to the character of the supply slope and seafloor relief, where hybrid beds are invoked to develop during periods of disequilibrium in out-of-grade slopes.

The mechanisms of formation and evolution of flows that deposit hybrid beds have been significantly studied and debated over the past decades. The aim of this study is to utilize techniques not commonly used in this area, namely Laser-Diffraction Grain-Size Analysis and End-Member Modelling Analysis (EMMA) to undertake a detailed study of lateral and down-dip changes within targeted deposits, to interpret more accurately how and when turbulent to laminar fluctuations occur, as well as adding quantitative analysis to previously established qualitative models. Samples were taken from the Marnoso-Arenacea Formation, the Castagnola Formation, and the Gottero Formation.

Initial findings show significant correlation between grain-size distribution from similar facies across different formations. Despite variability in the median grain-size between formations, similar end members can be extracted from each, indicating deposition under similar flow conditions.