High resolution <sup>40</sup>AR/<sup>39</sup>AR chronostratigraphy of the Late Cretaceous El Gallo Formation, Baja California del Norte, Mexico — Paul Randall Renne (1991) | RDL Network
Laser probe 40 Ar/ 39 Ar analyses of individual sanidine grains from four tuffs in the alluvial Late Cretaceous (Campanian) El Gallo Formation yield statistically distinct mean dates ranging from 74.87±0.05 Ma to 73.59±0.09 Ma. The exceptional precision of these dates permits calculation of statistically significant sediment accumulation rates that are much higher than passive sediment loading would cause, implying rapid tectonically induced subsidence. The dates bracket tightly the age of important dinosaur and mammalian faunas previously reported from the El Gallo Formation. The dates support an age less than 73 Ma for the Campanian/Maastrichtian stage boundary, younger than indicated by several currently used time scales. Further application of the single grain 40 Ar/ 39 Ar technique may be expected to greatly benefit stratigraphic studies of Mesozoic sedimentary basins and contribute to calibration of biostratigraphic and magnetostratigraphic time scales.
Carl C. Swisher, José Manuel Grajales-Nishimura, Alessandro Montanari, Stanley V. Margolis, Philippe Claeys, Walter Álvarez, Paul Randall Renne, Esteban Cedillo-Pardoa, F. J. Maurrasse, Garniss H. Curtis, Jan Smit, Michael McWilliams
Discussion(0)
No comments yet. Be the first to comment.