2009 Chapters (Layout Features)

Mega Tsunami of the World Oceans: Chevron Dune Formation, Micro-Ejecta, and Rapid Climate Change as the Evidence of Recent Oceanic Bolide Impacts

Gusiakov, Viacheslav; Abbott, Dallas Helen; Bryant, Edward A.; Masse, W. Bruce; Breger, Dee Lewis

This paper deals with the physical and environmental effects resulting from oceanic impacts by sizable comets, and the rates and risks associated with such cosmic impacts. Specifically, we investigate two sets of probable oceanic impact events that occurred within the last 5,000 years, one in the Indian Ocean about 2800 BC, and the other in the Gulf of Carpentaria (Australia) about AD 536. If validated, they would be the most energetic natural catastrophes occurring during the middle-to-late Holocene with large-scale environmental and historical human effects and consequences. The physical evidence for these two impacts consists of several sets of data: (1) remarkable depositional traces of coastal flooding in dunes (chevron dunes) found in southern Madagascar and along the coast of the Gulf of Carpentaria, (2) the presence of crater candidates (29-km Burckle crater about 1,500 km southeast of Madagascar which dates to within the last 6,000 years and 18-km Kanmare and 12-km Tabban craters with an estimated age of AD 572±86 in the southeast corner of the Gulf of Carpentaria), and (3) the presence of quench textured magnetite spherules and nearly pure carbon spherules, teardrop-shaped tektites with trails of ablation, and vitreous material found by cutting-edge laboratory analytical techniques in the upper-most layer of core samples close to the crater candidates. Although some propose a wind-blown origin for V-shaped chevron dunes that are widely distributed around the coastlines of the Indian Ocean and in the Gulf of Carpentaria, we have evidence in favor of their mega tsunami formation. In southern Madagascar we have documented evidence for tsunami wave run-up reaching 205 m above sea-level and penetrating up to 45 km inland along the strike of the chevron axis. Subtly the orientation of the dunes is not aligned to the prevailing wind direction, but to the path of refracted mega-tsunami originating from Burckle impact crater. The results of our study show that substantive oceanic comet impacts not only have occurred more recently than modeled by astrophysicists, but also that they have profoundly affected Earth’s natural systems, climate, and human societies. If validated, they could potentially lead to a major paradigm shift in environmental science by recognizing the role of oceanic impacts in major climate downturns during the middle-to-late Holocene that have been well documented already by different techniques (tree-ring anomalies, ice-, lake- and peat bog-cores).