Meteorite impacts as responsible for lunar retreat deceleration in the Cambrian boundary. Proterozoic clues and the role of Puncoviscana rhythmites data, northwestern Argentina.

LÓPEZ DE AZAREVICH, V.; AZAREVICH, M.B.

Resúmenes XIV RAS: Explorando la Patagonia

AAS

Lugar: La Plata; Año: 2014; p. 160 - 161

Statistical analyses with Fast Fourier Transforms (FFT) carried out on tidal rhythmites from ElatinaFormation-Australia (620 Ma, Sonett et al. 1996, and literature therein) allowed calculation of an Earth-Moondistance of 3.709 e08 meters. Results obtained on Puncoviscana Formation?s rhythmite sequences in NWArgentina (523 Ma, López de Azarevich, 2010; López de Azarevich et al., 2010) determined a separation of3.7608 e08 m between the Earth and the Moon with less than 5% error.The calculated lunar retreat is 6.48 cm/yrfor Ediacaran-Early Cambrian range. Results highlight a slightly deceleration of the lunar retreat from thecalculated value of 7.01 cm/yr from rhythmite data of the 900 Ma Big Cottonwood sequences together withthose from Elatina Formation during the current research. Deceleration was in order of 0.5 cm/year previous toPuncoviscana sedimentation, evidenced by an inflection point in the lunar retreat graphic (Fig. 1).This astronomic configuration of the Earth-Moon system was consequence of great magnitude episodeoccurred within the celestial alignment in the 100 Ma time span among deposition of Elatina (Ediacara,Australia) and Puncoviscana (Neoproterozoic-Early Cambrian, Argentina) sequences. A major astronomicepisode is registered on Earth by that time due to collision of the Beaverhead (600 Ma), Acraman (590 Ma) andSpieder (~570 Ma) meteorites (Compston et al. 1987; Grieve 1991). The impact craters are allocated in USA andSouth Australia respectively. Acraman generated a 160 km-diameter crater, Spider and Beaverhead were muchsmaller with 13 and 15 km-diameter (Grieve, 1991).