Probing the hydrothermal system of the Chicxulub impact crater

The ~180-km-diameter Chicxulub peak-ring crater and ~240-km multiring basin, produced by the impact that terminated the Cretaceous, is the largest remaining intact impact basin on Earth. International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364 drilled to a depth of 1335 m below the sea floor into the peak ring, providing a unique opportunity to study the thermal and chemical modification of Earth’s crust caused by the impact. The recovered core shows the crater hosted a spatially extensive hydrothermal system that chemically and mineralogically modified ~1.4 × 105 km3 of Earth’s crust, a volume more than nine times that of the Yellowstone Caldera system. Initially, high temperatures of 300° to 400°C and an independent geomagnetic polarity clock indicate the hydrothermal system was long lived, in excess of 106 years

Globally distributed iridium layer preserved within the Chicxulub impact structure

The Cretaceous-Paleogene (K-Pg) mass extinction is marked globally by elevated concentrations of iridium, emplaced by a hypervelocity impact event 66 million years ago. Here, we report new data from four independent laboratories that reveal a positive iridium anomaly within the peak-ring sequence of the Chicxulub impact structure, in drill core recovered by IODP-ICDP Expedition 364. The highest concentration of ultrafine meteoritic matter occurs in the post-impact sediments that cover the crater peak ring, just below the lowermost Danian pelagic limestone. Within years to decades after the impact event, this part of the Chicxulub impact basin returned to a relatively low-energy depositional environment, recording in unprecedented detail the recovery of life during the succeeding millennia. The iridium layer provides a key temporal horizon precisely linking Chicxulub to K-Pg boundary sections worldwide

Phase-averaged scanning stereoscopic PIV measurement for classification of vortex regime of synthetic jet in cross flow

A synthetic jet is one of flow control devices that can topologically disturb surrounding flow field by adding periodic injection and suction of surrounding fluid using an oscillating membrane through an orifice. This device can be applied to the downsized fluid machinery without a net mass injection of fluid for the simplified structure. In this study, the phase-averaged three-dimensional flow structures of the synthetic jet in laminar cross flow were measured by the phaselocked scanning stereoscopic PIV. The synthetic jet has a round orifice with a diameter of D = 1.0 mm. Stokes number and dimensionless stroke length were ranged from 6.3 to 12.7 and from 2.67 to 16.0, respectively. Reynolds number of the cross flow based on channel height was 1300. The vortex structure of the synthetic jet in cross flow was drastically changed depending on these parameters. According to the measured 3D vortex structure, the parameter map for the classification of vortex regime was obtained