THE VERTICAL DISTRIBUTION OF THE ALLUVIAL CHEMO-FACIES OF BOUMERZOUG WADI, CONSTANTINE, NORTHEASTERN ALGERIA: PALEOENVEROMENTAL SIGNIFICANCE AND CLIMATE EVOLUTION

The authorities of Constantine city have been working on the redevelopment and calibration of the Rhumel and Boumerzoug wadis since 2015. The latter calebrage works caused great damage to the banks, thus affecting the Quaternary geological formations in place (alluvial terraces, flood plains). A multidisciplinary research project based on a geomorphological and sedimentological approach was quickly set up to create a scientific data base before their total destruction and loss of physical traces all along the wadis. The present study focuses on the sedimentological and geochemical analysis of the alluvial deposits of Boumerzoug wadi in order to describe the sediments, to reconstitute their nature, and to interpret both the climatic evolution and the paleo-environments of the region. Sedimentological and geochemical results confirm the succession of deposition cycles linked to progressive climate change.

Mars and the ESA Science Programme - the case for Mars polar science

Current plans within the European Space Agency (ESA) for the future investigation of Mars (after the ExoMars programme) are centred around participation in the Mars Sample Return (MSR) programme led by NASA. This programme is housed within the Human and Robotic Exploration (HRE) Directorate of ESA. This White Paper, in response to the Voyage 2050 call, focuses on the important scientific objectives for the investigation of Mars outside the present HRE planning. The achievement of these objectives by Science Directorate missions is entirely consistent with ESA’s Science Programme. We illustrate this with a theme centred around the study of the Martian polar caps and the investigation of recent (Amazonian) climate change produced by known oscillations in Mars’ orbital parameters. Deciphering the record of climate contained within the polar caps would allow us to learn about the climatic evolution of another planet over the past few to hundreds of millions of years, and also addresses the more general goal of investigating volatile-related dynamic processes in the Solar System.

Erosion of the Himalaya-Karakoram recorded by Indus Fan deposits since the Oligocene

The Cenozoic erosion history of the Himalaya-Karakoram, which is a function of tectonically driven uplift and monsoon climatic evolution in South Asia, remains elusive, especially prior to the Miocene. Here, we present a multiproxy geochemical and thermochronological analysis of the oldest samples available from the Arabian Sea, which we used to investigate the erosion history of the Himalayan and Karakoram orogenic system. The Indus Fan records rapid and sustained erosion of the Himalayan-Karakoram mountains from before 24 Ma (ca. 30) to ca. 16 Ma concurrent with changing provenance from the Indian (Himalayan) and Eurasian plates. Our data, combined with previous studies of younger Indus Fan deposits, indicate that the mid-to-late Cenozoic erosion history of the Himalayan-Karakoram mountains is overall consistent with a vigorous monsoonal climate from the late Oligocene to middle Miocene and with changes in global climate in the late Miocene, whereas erosion and deposition are relatively insensitive to changes in sources and rock erodibility. Although tectonic processes were active throughout, we suggest that the erosional signatures of the Himalayan-Karakoram mountains from the Indus Fan largely preserve a record of climate changes since the Oligocene.

Central Asian modulation of Northern Hemisphere moisture transfer over the Late Cenozoic

Earth’s climatic evolution over the last 5 million years is primarily understood from the perspective of marine mechanisms, however, the role of terrestrial feedbacks remains largely unexplored. Here we reconstruct the last 5 million years of soil moisture variability in Central Asia using paleomagnetism data and isotope geochemistry of an 80 m-thick sedimentary succession at Charyn Canyon, Kazakhstan. We identify a long-term trend of increasing aridification throughout the period, along with shorter-term variability related to the interaction between mid-latitude westerlies and the Siberian high-pressure system. This record highlights the long-term contribution of mid-latitude Eurasian terrestrial systems to the modulation of moisture transfer into the Northern Hemisphere oceans and back onto land via westerly air flow. The response of Earth-surface dynamics to Plio-Pleistocene climatic change in Central Asia likely generated terrestrial feedbacks affecting ocean and atmospheric circulation. This missing terrestrial link elucidates the significance of land-water feedbacks for long-term global climate.

Climate changes across Oceanic Anoxic Event 1a: new data from the Boreal realm

<div><span>Our understanding of the climatic evolution during the early Cretaceous in general, and the Oceanic Anoxic Event 1a (OAE-1a) in peculiar, is widely derived from the investigation of Tethyan localities, leaving large uncertainties about their significance on a global scale. In this study, we have performed high-resolution clay-mineral assemblage analyses in the upper Hauterivian to lower Aptian of the </span><span>North Jens-1 core, located in the Danish central graben that was part of the Boreal realm. High amount of detrital Kaolinite is observed throughout the core, indicating the presence of a local, kaolinite-rich source. A long-term decline in Kaolinite content is occurring from the lower Hauterivian to the lowermost, pre-OAE-1a Aptian, followed by a sharp rise within the OAE-1a. This trend is similar to the one observed in the Tethyan realm, indicating a supra-regional climatic evolution from humid conditions in the late Hauterivian toward drier conditions in the latest Barremian – earliest Aptian, followed by renewed humid conditions during the unfolding of OAE-1a. Precise timing of climate change during the OAE-1a differs however in between the Tethyan and Boreal realm. Shift toward humid conditions coincides hence with the onset of OAE-1a (segment C3) in the Tethyan realm, followed by a return to drier conditions in the second half of OAE-1a. In the Boreal realm, the onset of OAE-1a is characterized by a relatively dry climate, followed by the installation of humid climate during the mid-OAE-1a (segments C4-C5) that persists through the remainder of the early Aptian. Across latitudinal belts, there is thus a non-linear change in precipitation pattern during the unfolding of OAE-1a. Similar observations have been made for other OAEs, suggesting more complex weathering feedback mechanism during hyperthermal events than generally assumed.</span></div>

Central Asian Modulation of Northern Hemisphere Moisture Transfer Over the Late Cenozoic

Earth’s climatic evolution over the last 5 million years (Myr) is primarily understood from the perspective of marine mechanisms. While changes in ocean circulation go a long way towards explaining the transport of moisture onto the continents, the role of terrestrial feedbacks in the opposite direction remain largely unexplored. Here we reconstruct the last 5 Myr of rainfall variability in Central Eurasia from an 80 m-thick sedimentary succession at Charyn Canyon, Kazakhstan. Charyn Canyon lies at the centre of the world’s largest land mass and at the present-day transition between the mid-latitude westerlies and Siberian high-pressure system. Our record provides the first opportunity to interrogate long-term interactions between mid-latitude westerly and high latitude climate systems over the Eurasian continent. This missing terrestrial link highlights the significance of land-water feedbacks for long-term global climate.