Impact cratering and the evolution of planetary surfaces in the solar system – The Chicxulub impact

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Impacts of asteroid and comets constitute major geologic processes shaping the
surfaces and evolution of planetary bodies. Impacts produce deep transient
cavities, with excavation to deep crustal levels, fragmentation, and removal of
large rock volumes. Formation of complex craters involves high pressures and
temperatures resulting in intense deformation, fracturing and melting. Here, we
analyze the crater-forming impacts and their effects on the Earth´s climate,
environment and life-support systems, in relation to the Cretaceous/Paleogene
(K/Pg) boundary. The boundary represents one of the major extinction events in
the Phanerozoic, which affected about 75 % of species. It is marked by a clay
layer globally distributed that is characterized by anomalous contents of
iridium and platinum group elements, marking the occurrence of a large bolide
impact. Studies have examined the age, stratigraphic correlations and
composition of the boundary layer, establishing a genetic association to the
Chicxulub impact in the Yucatan peninsula in the Gulf of Mexico. The Chicxulub
crater is a ~200 km diameter structure with peak ring and multi-ring morphology.
Impact generated a transient cavity some 20-25 km deep resulting in intense
deformation and shaking, which is recorded in the breccias and debris flow
deposits in the Gulf of Mexico and Caribbean Sea area. Impact was on a shallow
carbonate platform and resulted in huge tsunamis and in injection of CO2 and
sulfur components into the atmosphere. Effects of impacts in the environment and
climate of the Earth have been intensely investigated, mainly in relation to the
mass extinction, where the affectation in the evolution patterns was profound
and long-lasting. Effects of the K/Pg impact on the ecosystems extended for a
long period of several millions of years. The disappearance of large numbers of
species including complete groups severely affected the biodiversity and
ecosystem composition in the marine and continental realms.