Uncovering the Ediacaran phosphorus cycle.

Phosphorus is a limiting nutrient that is thought to control oceanic oxygen levels to a large extent. A possible increase in marine phosphorus concentrations during the Ediacaran Period (about 635-539 million years ago) has been proposed as a driver for increasing oxygen levels. However, little is known about the nature and evolution of phosphorus cycling during this time.

Seawater-buffered diagenesis, destruction of carbon isotope excursions, and the composition of DIC in Neoproterozoic oceans.

Carbonate sediments of nonglacial Cryogenian (659 to 649 Ma) and early Ediacaran (635 to 590 Ma) age exhibit large positive and negative δC excursions in a shallow-water marine platform in northern Namibia. The same excursions are recorded in fringing deep-sea fans and in carbonate platforms on other paleocontinents. However, coeval carbonates in the upper foreslope of the Namibian platform, and to a lesser extent in the outermost platform, have relatively uniform δC compositions compatible with dissolved inorganic carbon (DIC) in the modern ocean.

Earthquake lubrication and healing explained by amorphous nanosilica.

During earthquake propagation, geologic faults lose their strength, then strengthen as slip slows and stops. Many slip-weakening mechanisms are active in the upper-mid crust, but healing is not always well-explained. Here we show that the distinct structure and rate-dependent properties of amorphous nanopowder (not silica gel) formed by grinding of quartz can cause extreme strength loss at high slip rates.