Africa is experiencing a renewed natural resource boom. Heightened demand for the continent’s vast reserves of critical minerals and metals for green energy and technological applications, as well as its ability to serve oil and gas markets in a time of geopolitical turmoil, have triggered increased international interest and investment in African resource sectors. As in previous commodity booms, resource-rich African governments are articulating a desire to leverage natural resource wealth for economic growth and human development. Yet this promise also brings peril, as natural resource endowments have in the past generally failed to translate into improved living standards and economic growth for most resource-rich African states. Whether “this time will be different” for developmental outcomes will be shaped not just by resource endowments, but critically, by the interplay between global geopolitical dynamics, domestic political institutions, and local governance processes.
The JPL rover Perseverance's investigations of Jezero crater's floor reveal that the ultramafic S & eacute;& iacute;tah formation and the overlying mafic M & aacute;az formation are deformed into a broad, low-amplitude structural dome. Mastcam-Z stereo images processed into digital outcrop models, together with RIMFAX ground-penetrating radar profiles, were used to reconstruct the three-dimensional stratal geometry of both units along a SW-NE transect across a southern domain of the dome called south S & eacute;& iacute;tah. Measurements from 3-D reconstructions show a progression from sub-horizontal layers in the central parts of the dome to dips <20 degrees away from the dome on its flanks, with M & aacute;az and underlying S & eacute;& iacute;tah layers dipping concordantly. RIMFAX profiles and imaging around the dome confirm that limb dips are continuous into the subsurface and form a flat-crested composite quaquaversal fold structure. S & eacute;& iacute;tah rocks in the fold core are up to 17 m higher than adjacent M & aacute;az lava flows, despite stratigraphically underlying them, a relationship attributed to structural uplift. Fold geometry, wavelength (similar to 1 km), and amplitude (similar to 30-50 m), match models of forced folding produced by inflation of shallow igneous intrusions. The most likely cause is the emplacement of a sill or laccolith beneath the crater floor, generating elastic bending of the overlying layers. This intrusion-driven uplift explains S & eacute;& iacute;tah's elevated position, constrains the deformation history of Jezero's crater floor units post-emplacement of the S & eacute;& iacute;tah and M & aacute;az formations, and supports a significant role for shallow magmatic intrusion in shaping intracrustal structures on Mars.
The contributions of potential drivers of uplift and erosion in subduction zone forearcs over geologic time remain unknown. Proposed drivers include coseismic and interseismic earthquake cycle deformation associated with upper-plate forearc faults and the underlying subduction interface. The Hikurangi subduction zone (HSZ), along the eastern North Island of Aotearoa New Zealand, provides a unique location to examine these controls, given both along-strike variations in subduction zone coupling, as well a record of vertical motion from modern and prehistoric earthquakes on forearc faults and the plate interface. There, the Palliser-Kidnappers coastline (PKC) obliquely parallels the plate boundary in proximity to a number of forearc faults and spans a transitional boundary between currently locked and freely slipping portions of the subduction interface. Using digital topographic analysis and catchment-averaged erosion rates from cosmogenic Be-10, we examined the geomorphology of the HSZ forearc to evaluate connections between plate coupling and forearc erosion and uplift. In general, we find overall low concentrations of Be-10 and consequently high rates of erosion that mimic coastal uplift along the PKC, with high rates (>1 mm year(-1)) of erosion concentrated in the south near Cape Palliser. There, the southern Aorangi Range exposes deeper basement terrane rocks that are incised by the steepest fluvial drainages along the PKC, with positive correlation between normalised channel steepness (k(sn)), erosion rate and Late Pleistocene-Holocene uplift rates from marine terraces. Our findings indicate the highest forearc uplift rates occur above the narrow, locked portion of the HSZ, in an area near offshore oblique contractional deformation on the Palliser-Kaiwhata fault.
Quantification of black carbon on snow in the Cascade Range is needed due to increasing wildfire intensity and frequency. Here, the benzenepolycarboxylic acid (BPCA) molecular method was used to measure dissolved black carbon (DBC) in snow, nearby rivers, streams, and supraglacial melt collected in 2022 and 2023 from Mount Baker and Mount Rainier. The average DBC concentration in snow was 9 +/- 4 mu g-C/L and 10 +/- 6 mu g-C/L in stream, river, and supraglacial meltwater samples. The DBC method provides black carbon source identification via BPCA characterization. DBC concentrations and BPCA proportions were compared to modeled smoke deposition from the Navy Aerosol Analysis and Prediction System reanalysis model. In both years, total deposition from May through October was approximately 670 mg/m2. However, early season smoke deposition (May through July) was four times higher in 2023 than 2022, indicating seasonal variability in the timing of deposition. Dry deposition accounted for over 80 percent of total late season smoke deposition (August through October) in both 2022 and 2023, while wet deposition accounted for 75 and 30 percent of total early season deposition in 2022 and 2023, respectively. The largest smoke deposition events on Mount Baker coincided with precipitation events and enrichment of benzenepentacarboxylic acid, a marker of biomass burning, in snow. Using the Snow, Ice, and Aerosol Radiative model, we estimated an average albedo of 0.68 +/- 0.03. The resulting instantaneous radiative forcing attributable to the presence of BC in snow ranged from 3 to 16 W/m2, with an average of 7.47 +/- 3.3 W/m2.
Prior research on the value relevance of sales has produced mixed results, largely because it is difficult to isolate the information content of sales. Using a unique dataset of interim sales disclosures by retail firms, this study demonstrates that stock market investors react strongly to these stand-alone sales announcements, and that the value relevance of sales information arises primarily from growth in same-store sales (SSS). In a decomposition analysis, we find that interim sales disclosures provide more information to the market than earnings announcements and other disclosure events. We also find that interim SSS growth predicts a firm's future earnings and operating cash flows. Overall, this study presents new evidence on the value relevance of sales and contributes to the ongoing debate about whether U.S. retail companies should continue to provide interim sales disclosures.
