February Geology and GSA Today media highlights

Paleoecology reconstruction from trapped gases in a fulgurite from the late Pleistocene of the Libyan Desert
Rafael Navarro-González, Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares, Laboratorio de Quimica de Plasmas y Estudios Planetarios, México City DF 04510, México; et al. Pages 171-174.

Lightning is a transient atmospheric event that can be petrified when it strikes the ground, heating, melting, and fusing the sand in soils to form glass tubes known as fulgurites. Fulgurites found in the Libyan Desert, the hyperarid core of the Saharan Desert, indicate that the region received rain in the past. The discovery of gases such as carbon dioxide (CO2), carbon monoxide (CO), and nitric oxide (NO) trapped in glassy bubbles of fulgurites has provided clues on the ecological environment at the time of lightning strike. The gases are not of atmospheric origin but rather are the result of the oxidation of organic matter present in the soil. Isotopic analysis of the gases further reveals that the organic matter was produced by plants that adapted to live in hot and arid zones. The timing of fulgurite formation was obtained for the first time by thermoluminescence dating, indicating that the event took place 15,000 years ago, in the late Pleistocene. The results imply that the semiarid Sahel region, which is currently located at 17°N, reached at least to 24°N at that time. The results also demonstrate that fulgurite gases and luminescence geochronology can be used in quantitative paleoecology.

Formation of the 1300-km-wide intracontinental orogen and postorogenic magmatic province in Mesozoic South China: A flat-slab subduction model
Zheng-Xiang Li, University of Western Australia, School of Earth and Geographical Sciences, Tectonics Special Research Centre, Crawley WA 6009, Australia; et al. Pages 179-182.

In a soon-to-be dinosaur-infested continent covered by calm sea water, a mountain belt emerged out of water and swept from one end of the continent almost to the other like a weather front. Where the mountain belt had just swept through, newly emerged mountain ranges again submerged into a shallow sea, only to re-emerge soon afterward as volcanos started to erupt over the continent. All this happened in a time interval of 100 million years in South China. New evidence suggests that such dramatic continental-scale vertical movements were caused by horizontal subduction of an oceanic plateau, which may have occurred more often in Earth’s history than people have realized.