Institutskolloquium

Eslem Ben Arous

Putting a Pin in the Map!’: recent developments in ESR Dating for the Middle Stone Age of West Africa by Eslem Ben Arous; PACEA Research Unit - University of Bordeaux (Pessac, France), MPI-EVA and MPI-GEA

Abstract:

West Africa remains one of the least chronologically constrained regions of the African continent for the Pleistocene, despite its importance for understanding the diversity, dispersal, and evolution of human populations across Africa. This talk presents recent results from the application of electron spin resonance (ESR) dating to optically bleached quartz from Middle Stone Age archaeological contexts in West Africa. It will address the potential of ESR dating to establish chronological constraints for archaeological deposits in Côte d’Ivoire and Senegal, with particular attention to the challenges associated with assessing age uncertainties.

The new ESR results help fill an important chronological gap in the region, providing age estimates for archaeological contexts that have previously been difficult to date and contributing to the development of a Pleistocene chronological framework. Beyond individual sites, these results highlight the potential of improved chronologies to reshape our understanding of human evolution and population dynamics in West Africa. Rather than viewing West Africa as a geographical gap in the African Palaeolithic record, increasingly robust chronological frameworks suggest that part of this apparent absence may reflect limited archaeological research and dating rather than an absence of human.

Dr. Glenn Gaetanni Woods Hole Oceanographic Institution

Experimental constraints on the damp peridotite solidus and potential temperature of the oceanic mantle

Oceanic crust forms as mantle peridotite ascends and partially melts beneath Earth’s global system of oceanic spreading centers. Two factors control the depth at which melting begins: mantle temperature and the pressure-temperature conditions that define the peridotite solidus. Geophysical detection of partial melt combined with experimental determination of the solidus can be used to estimate the temperature of mantle beneath ridges. A major uncertainty, however, derives from the fact that “nominally anhydrous” minerals comprising peridotite contain small amounts of hydrogen that significantly lowers the peridotite solidus. This shifts the onset of partial melting to greater depths and, thereby, alters both the volume of mantle involved and the maximum extent of partial melting. While it is widely recognized that the melting point of “damp” peridotite is dramatically lower than the truly anhydrous solidus, the influence of the 50–200 μg/g H₂O thought to be present in the oceanic upper mantle has been difficult to quantify experimentally. To address this, we developed a new experimental approach that uses olivine spheres ~300 µm in diameter as hygrometers, taking advantage of rapid hydrogen diffusion in olivine to accurately determine hydrogen concentrations present in high‑pressure melting experiments. We used this approach to quantify the solidus temperature for peridotite containing ~145 μg/g dissolved H₂O at 1.0 to 2.5 GPa. Our results show that the damp peridotite solidus is significantly hotter than previously estimated. When these new experimental constraints are combined with geophysical observations of partial melt beneath the East Pacific Rise, they imply that current estimates of mantle potential temperature beneath fast‑spreading ridges should be increased by approximately 60 °C. This upward revision has implications for how we interpret melt generation, mantle dynamics, and thermal structure beneath mid‑ocean ridges – topics central to ongoing research in mantle geochemistry and geodynamics.

Digital Characterization of Fracture Networks and Fluid Flow Behaviour in Rocks: New Methods and Applications by Raghubeer Rai, Department of Geology and Geophysics, Indian Institute of Technology Kharagpur (India)

Abstract:

Fracture networks play a fundamental role in controlling fluid flow through geological materials. Their geometrical, topological, and spatial characteristics influence the hydraulic properties and directional flow behaviour of fractured rocks. Quantitative characterization of these features helps establish the relationship between fracture network properties and fluid flow.

This talk presents digital approaches, including image-based analysis, for characterizing fracture networks and fracture surface roughness, with an emphasis on their implications for fluid flow behaviour in rocks. It will first introduce the application of Gray Level Co-occurrence Matrix (GLCM)-based image analysis to quantify the textural anisotropy of fracture networks and investigate its relationship with permeability anisotropy. The talk will then explore Fourier-based characterization of fracture roughness and its evolution in thermally treated sandstone from the Gondwana Supergroup, Chhattisgarh, India.

By bringing together image-based statistical analysis and quantitative fracture-surface characterization, the presentation will highlight how digital methods can provide insights into fracture network properties and their implications for understanding fluid flow in fractured geological systems.

More information to follow

More information to follow

More information to follow