Hacia una teoría galáctica del catastrofismo terrestre

Abstract

The contemporary theories of terrestrial catastrophism are briefly reviewed. The role of Apollo-objects and some historical references to Tunguska-type cases are shortly described. Since the likely galactic origin of periodicities in the terrestrial record, the possibility that encounters with GMCs perturbed the Oort cloud is analyzed. The galactic orbits of the Sun and nearby GMCs were determined for the last 40 Myr. The result is that the Sun encountered probably Ori OBI and Mon OBI Clouds in coincidence with the dates of the Miocene and Eocene mass extinctions (see Figs.l, 2, 3 and 4). It is proposed that the Sun was for 250 Myr captive of a supercloud or association of GMCs (Gould's belt), of which the progenitors of Ori OBI and Mon OBI formed part. A computer simulation of Sun's orbit relative to the hypothetical cloud, to which the Sun would have been physically attached, is presented (see Figs. 5 and 6). The 25-30/13-15 Myr quasi-periodicities in the terrestrial record can be explained by the model.