Discovered in 1988 by R. Oslisly and B. Peyrot, Elarmékora is a high terrace that, today, is situated 175 m above the Ogooué River in the historical complex of Elarmékora, attached to the Lopé ...National Park in Gabon, a World Heritage site since 2007. The site yielded a small lithic assemblage, including mainly cobble artefacts embedded within the 1 m thick alluvial material. Based on geomorphological and palaeoclimatological criteria, the preliminary dating suggested an age of 400 ka. However, Elarmékora could be a key site for Atlantic Central Africa if this lithic industry can be dated absolutely. In 2018 and 2019, two field trips were organized to collect surface samples as well as samples in vertical depth profiles with the aim of measuring their
-produced cosmogenic nuclide (
Be and
Al) content. Results suggest a surface abandonment between 730 and 620 ka ago representing a minimum age for the cobble artefacts. Concurrently, technological reappraisal of the artefacts suggests an atypical lithic industry that should, for the moment, be considered as 'undiagnostic' Earlier Stone Age. This age bracketing may be compared with a similar age range obtained for prehistoric occupations in Angola using the same approach. This age will place Elarmékora among the oldest evidence for the presence of hominins in western Central Africa and raises the question of a 'West Side Story' to early human dispersals in Africa. This article is part of the theme issue 'Tropical forests in the deep human past'.
Discovered in 1988 by R. Oslisly and B. Peyrot, Elarmékora is a high terrace that, today, is situated 175 m above the Ogooué River in the historical complex of Elarmékora, attached to the Lopé ...National Park in Gabon, a World Heritage site since 2007. The site yielded a small lithic assemblage, including mainly cobble artefacts embedded within the 1 m thick alluvial material. Based on geomorphological and palaeoclimatological criteria, the preliminary dating suggested an age of 400 ka. However, Elarmékora could be a key site for Atlantic Central Africa if this lithic industry can be dated absolutely. In 2018 and 2019, two field trips were organized to collect surface samples as well as samples in vertical depth profiles with the aim of measuring their
in situ
-produced cosmogenic nuclide (
10
Be and
26
Al) content. Results suggest a surface abandonment between 730 and 620 ka ago representing a minimum age for the cobble artefacts. Concurrently, technological reappraisal of the artefacts suggests an atypical lithic industry that should, for the moment, be considered as ‘undiagnostic’ Earlier Stone Age. This age bracketing may be compared with a similar age range obtained for prehistoric occupations in Angola using the same approach. This age will place Elarmékora among the oldest evidence for the presence of hominins in western Central Africa and raises the question of a ‘West Side Story’ to early human dispersals in Africa.
This article is part of the theme issue ‘Tropical forests in the deep human past’.
Based on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during ...the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the "AMOC-corrected" temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms.
We report the discovery of large accumulations of micrometeorites on the Myr-old, glacially eroded granitic summits of several isolated nunataks in the Victoria Land Transantarctic Mountains. The ...number (>3,500) of large (>400 μm and up to 2 mm in size) melted and unmelted particles is orders of magnitudes greater than other Antarctic collections. Flux estimates, bedrock exposure ages and the presence of almost equal to0.8-Myr-old microtektites suggest that extraterrestrial dust collection occurred over the last 1 Myr, taking up to 500 kyr to accumulate based on 2 investigated find sites. The size distribution and frequency by type of cosmic spherules in the >200-μm size fraction collected at Frontier Mountain (investigated in detail in this report) are similar to those of the most representative known micrometeorite populations (e.g., South Pole Water Well). This and the identification of unusual types in terms of composition (i.e., chondritic micrometeorites and spherulitic aggregates similar to the almost equal to480-kyr-old ones recently found in Antarctic ice cores) and size suggest that the Transantarctic Mountain micrometeorites constitute a unique and essentially unbiased collection that greatly extends the micrometeorite inventory and provides material for studies on micrometeorite fluxes over the recent (almost equal to1 Myr) geological past.
10Be and 36Cl Cosmic Ray Exposure (CRE) dating performed on river polished surfaces of river gorges in a mountain-to-sea river system in the French SW Alps highlights transient erosional events ...involving incision rates >10 mm a−1. These events took place during the last two major deglaciation phases following (1) the Last Glacial Maximum (LGM) at 16–14 ka, (2) the Younger Dryas at 8–11 ka, and during the warm and humid Holocene climatic optimum at 4–5 ka. These periods of high incision rates (3–>30 mma−1) alternated with periods of low incision rates (<1 mm a−1), which probably correspond to a long-term equilibrium between incision and relative uplift. The Alpine river staircase shape profiles evidence local and transient responses that are ascribed to cumulate disequilibrium after the long-time-spanned glaciations. After each glaciation, rivers rush down to get closer to their equilibrium profile. Incision is amplified both by the sediment discharge due to the erosion of moraines and by landslides triggered by the glacier retreat.
•Mountain gorges incision history is documented using CRE dating.•The gorges result from transient erosional events with incision rates >10 mm a−1.•High incision during the two last major deglaciation phases (LGM) at 16–14 ka, the Younger Dryas at 8–11 ka.•High incision during the warm and humid Holocene climatic optimum at 4–5 ka.•Periods of low incision rates (<1 mm a−1) for long-term equilibrium between incision and uplift.
We have previously shown that toll-like receptor-4 (Tlr4) is involved in obesity-induced inflammation in adipose tissue (AT). However, less is known about the role of Tlr2 in this process. To ...determine the involvement of this receptor in obesity-induced inflammation, we utilized male Tlr2
−/− mice that were backcrossed onto a mouse model of diet-induced obesity (DIO). Mice were fed either low-fat control (LFD) or high-fat diet (HFD)
ad libitum for 16 weeks. Despite negligible differences in body weight or energy intake, Tlr2
−/− mice were protected from HFD-induced adiposity as was evident by reduced epididymal fat pad weight and carcass lipid content. Corresponding with these effects was a blunted accumulation of F4/80-positive macrophages in AT of Tlr2
−/− mice. Furthermore, transcript abundance of proinflammatory mediators, including monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNFα) and nitric oxide synthase-2 (NOS2) in AT of Tlr2
−/− mice, was lower or less responsive to DIO. There were no significant differences in serum markers of insulin sensitivity (data not shown). However, adipocytes derived from stromal vascular cells (SVCs) isolated from AT of Tlr2
−/− mice had considerably greater basal and insulin-stimulated glucose uptake as compared with those obtained from Tlr2
+/+ mice. Furthermore, the absence of Tlr2
−/− precluded the induction of insulin resistance by zymosan A (ZymA) but not by palmitate. These data indicate that Tlr2 may be directly involved in HFD-induced inflammation and may also regulate basal and insulin-stimulated glucose uptake in adipocytes.
The ~400‐km‐long Talas‐Fergana Fault is one of a series of major right‐lateral strike‐slip faults that cross the Tien Shan Range. This fault has been recognized as active in the late Holocene and ...accommodates part of the deformation induced by the ongoing Indo‐Asian collision. The kinematics and the role of this strike‐slip fault are poorly understood with no large earthquakes reported in the instrumental or historical catalogs, and no well‐constrained geological slip‐rate estimates. Here we used high‐resolution satellite imagery to present a first detailed analysis of the fault segmentation. We identified nine geometric segments based on strike variations for the Talas‐Fergana Fault. Along the Kyldau segment, through morphological analyses of an offset alluvial fan and the application of multiple dating methods (10Be, 26Al, 36Cl, luminescence, and radiocarbon), we calculated a late Quaternary slip rate ranging from 2.2 to 6.3 mm/year. This rate is higher than the geodetic measurements, but the discrepancy can be partly explained if the Talas‐Fergana Fault accommodates shortening by counterclockwise rotation around a vertical axis. Paleoearthquakes identified by trenching indicate that at least two primary surface ruptures (and possibly a third) occurred in the past 3,800 years, and that no large earthquake has ruptured the Kyldau segment since at least 420 years B.P. (possibly within the last 2,700 years), making this fault segment a potential candidate to generate an earthquake with M > 7 in the near future.
Key Points
The 400‐km‐long Talas‐Fergana Fault (TFF) can be subdivided into nine geometric segments
A first geological slip rate of 2.2–6.3 mm/year is constrained by geochronological dating of an alluvial fan
The TFF may be associated with counterclockwise rotations around a vertical axis. This model reconciles geodetic and geologic slip rates
In the Argentera massif (French Southern Alps), large active landslides develop along strike of an active corridor of dextral strike-slip faults revealed by shallow ongoing seismicity. Glacially ...polished bedrock outcrops are offset by right-lateral strike-slip faults. Gravitational structures appear to be spatially connected to these active faults. Dating using the in situ-produced 10Be cosmogenic nuclide performed on glacial, tectonic and gravity surfaces. The late glacial–interglacial Holocene transition is constrained by 10Be ages between 12 and 15ka obtained on glacially polished surfaces. The main tectonic activity closely post-dates the main deglaciation event and is constrained by 10Be ages of 11 and 7–8ka obtained on fault scarps. Three successive periods of landsliding are recognized, at 11–12, 7–9 and 2.5–5.5ka. These Holocene ages were obtained on right-lateral strike-slip fault scarps indicating that recent Alpine tectonics are expressed by transcurrent movements. The discussed close age relationship between deglaciation and a tectonic pulse may suggest that post-glacial rebound and enhanced pore water pressure do influence seismogenic tectonic activity. Gravitational destabilizations at 11–12 and 7–9ka are coincidental with the main tectonic activity, and suggest tectonic shaking as a landslide trigger. The third gravitational destabilization at 2.5–5.5ka could be attributed either to slope weakness resulting from multiple low-magnitude earthquake events, as currently revealed by the seismic activity or to climatic causes during the wetter optimum climatic period. These early and middle Holocene ages coincide with a phase of large landslide throughout the Alps scale which suggests that these large gravitational mass movements could be related to combined effects of intense tectonic activity and transitions form cold and dry period to warm and wetter phase.
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