Mesozoic sedimentary cover sequences of the Congo Basin in the Kasai region, Democratic Republic of Congo

The Congo Basin represents one of the largest and least studied continental sedimentary basins in the world. The stratigraphy of cover sequences across the basin is poorly resolved and a somewhat simple stratigraphy has generally been applied with gross subdivision of the Mesozoic-Cenozoic cover sequences into a number weakly correlated units. Although these subdivisions are useful for broad, regional-scale correlations, investigation of drill cores and outcrop in the shallow, southern Kasai part of the basin, from Tshikapa to Kabinda, reveals considerable facies, provenance and thickness variations, suggesting a more complex depositional and stratigraphic history than previously recognized. This study now permits the subdivision of the sedimentary cover in the Kasai portion of the Congo Basin into five distinct depositional sequences consisting of (1) P1: Permo-Carboniferous glacio-lacustrine deposits correlative to the Lukuga Group; (2) J1: Jurassic-age arid to semi-arid laminated shales and siltstones and aeolian sandstones, interpreted as ephemeral lake and sand dune sequences with interspersed loess deposits and rare fluvial channel sequences (considered part of the historic Lualaba-Lubilash Supergroup—the lacustrine facies likely correlates with the Stanleyville Group, DRC and the Continental Intercalar Group, Angola); (3) C1 & C2: Lower Cretaceous locally heavy mineral-rich fluvial sandstone deposits and variably present basal conglomerate (correlated to the Loia Group, DRC and the Calonda Formation, Angola); (4) C3 & C4: Upper Cretaceous conglomerates of alluvial fan origin that grade upward into laminated shales and siltstones or well-sorted and rounded, fined grained sandstones representative of a semi-arid to arid depositional setting dominated by ephemeral lakes and small aeolian dunes, (equated to the Kwango Group, DRC and Angola) and (5) T1: fluvial, aeolian and lacustrine sediments of Paleogene age (correlated with portions of the Kalahari Group). The results convincingly suggest that this part of the Congo Basin is more structurally complex than previously appreciated, with multiple fault-bounded basement highs and depocenters that strongly influenced regional sedimentation patterns. Prolonged and sporadic displacement appears to have taken place along these faults, leading to heavily bisected basin morphology with uneven thickness and depth distributions between sequences. The deposition of Cretaceous sequences was coeval with two episodes of kimberlite emplacement, the first at ~120–130 Ma in northern Angola, and the second at ~70–80 Ma in the DRC, with gravel horizons within the Cretaceous fluvial successions (C1 and C3) known for their alluvial diamond concentration. The models developed provide a regional context for evaluation of alluvial diamond source areas and prospectivity

Ezetimibe added to statin therapy after acute coronary syndromes

BACKGROUND: Statin therapy reduces low-density lipoprotein (LDL) cholesterol levels and the risk of cardiovascular events, but whether the addition of ezetimibe, a nonstatin drug that reduces intestinal cholesterol absorption, can reduce the rate of cardiovascular events further is not known. METHODS: We conducted a double-blind, randomized trial involving 18,144 patients who had been hospitalized for an acute coronary syndrome within the preceding 10 days and had LDL cholesterol levels of 50 to 100 mg per deciliter (1.3 to 2.6 mmol per liter) if they were receiving lipid-lowering therapy or 50 to 125 mg per deciliter (1.3 to 3.2 mmol per liter) if they were not receiving lipid-lowering therapy. The combination of simvastatin (40 mg) and ezetimibe (10 mg) (simvastatin-ezetimibe) was compared with simvastatin (40 mg) and placebo (simvastatin monotherapy). The primary end point was a composite of cardiovascular death, nonfatal myocardial infarction, unstable angina requiring rehospitalization, coronary revascularization ( 6530 days after randomization), or nonfatal stroke. The median follow-up was 6 years. RESULTS: The median time-weighted average LDL cholesterol level during the study was 53.7 mg per deciliter (1.4 mmol per liter) in the simvastatin-ezetimibe group, as compared with 69.5 mg per deciliter (1.8 mmol per liter) in the simvastatin-monotherapy group (P<0.001). The Kaplan-Meier event rate for the primary end point at 7 years was 32.7% in the simvastatin-ezetimibe group, as compared with 34.7% in the simvastatin-monotherapy group (absolute risk difference, 2.0 percentage points; hazard ratio, 0.936; 95% confidence interval, 0.89 to 0.99; P = 0.016). Rates of pre-specified muscle, gallbladder, and hepatic adverse effects and cancer were similar in the two groups. CONCLUSIONS: When added to statin therapy, ezetimibe resulted in incremental lowering of LDL cholesterol levels and improved cardiovascular outcomes. Moreover, lowering LDL cholesterol to levels below previous targets provided additional benefit