Oceanic Extinction Research Articles

Multisphere Tectonics of the Earth System

AbstractThe fundamental theoretical framework of the Multisphere Tectonics of the Earth System is as follows: (1) It intends to extend the geotectonic studies from the crustal and lithospheric tectonics to the multisphere tectonics of the Earth system as a whole. (2) The global dynamics driven by both the Earth system and the cosmic celestial system: solar energy, multispheric interactions of the Earth system and the combined effects of the motions of celestial bodies in the cosmos system are the driving forces of various geological processes. (3) The Continent‐Ocean transformation theory: the continent and ocean are two opposite yet unified geological units, which can be transformed into each other; neither continent nor ocean will survive forever; there is no one‐way development of continental accretion or ocean extinction; the simple theory of one‐way continental accretion is regarded as invalid. (4) The continental crust and mantle are characterized by multiple layers, with different layers liable to slide along the interfaces between them, but corroboration is needed that continents move as a whole or even drift freely. (5) The cyclic evolution theory: the development of Earth's tectonics is not a uniform change, but a spiral forward evolution, characterized by a combination of non‐uniform, non‐linear, gradual and catastrophic changes; different evolutionary stages (tectonic cycles) of Earth have distinctive global tectonic patterns and characteristics, one tectonic model should not be applied to different tectonic cycles or evolutionary stages. (6) The structure and evolution of Earth are asymmetric and heterogeneous, thus one tectonic model cannot be applied to different areas of the world. (7) The polycyclic evolution of the continental crust: the continental crust is formed by polycyclic tectonics and magmatism, rather than simply lateral or vertical accretion. (8) The role of deep faults: the deep fault zones cutting through different layers of the crust and mantle usually play important roles in tectonic evolution. For example, the present‐day mid‐ocean ridge fault zones, transform fault zones and Benioff zones outline the global tectonic framework. Different tectonic cycles and stages of Earth's evolution must have their own distinctive deep fault systems which control the global tectonic framework and evolutionary processes during different tectonic cycles and stages. Starting from the two mantle superplumes Jason (Pacific) and Tuzo (Africa), the study of the evolutionary process of the composition and structure of the crust and mantle during the great transformation and reorganization of the Meso‐Cenozoic tectonic framework in China and the other regions of Asia is a good demonstration of theory of Multisphere Tectonics of the Earth System.

Contributors

Contributors

NOxproduction and rainout from Chicxulub impact ejecta reentry

AbstractThe Chicxulub impact 66.0 Ma ago initiated the second biggest extinction in the Phanerozoic Eon. The cause of the concurrent oceanic nitrogen isotopic anomaly, however, remains elusive. The Chicxulub impactor struck the Yucatán peninsula, ejecting 2 × 1015 kg of molten and vaporized rock that reentered globally as approximately 1023microscopic spherules. Here we report that modern techniques indicate that this ejecta generates 1.5 × 1014moles of NOx, which is enough to cause the observed nitrogen enrichment of the basal layer. Additionally, reentry‐based NO production would explain the anomalously heavy isotopic composition of the observed nitrogen. We include N, O, N2, O2, and NO species in simulations of nonequilibrium chemically reacting flow around a reentering spherule. We then determine the net production of NO from all the spherules and use turbulence models to determine how quickly this yield diffuses through the atmosphere. Upon reaching the stratosphere and troposphere, cloud moisture absorbs the NOxand forms nitric acid. We model this process and determine the acidity of the resulting precipitation, which peaks about 1 year after the impact. The precipitation ultimately reaches the upper ocean, where we assume that the well‐mixed surface layer is 100 m deep. We then model the naturally occurring carbonate/bicarbonate buffer and determine the net pH. We find that insufficient NOxreaches the ocean to directly cause the observed end‐Cretaceous oceanic extinction via acidification and buffer removal. However, the resulting nitrates are sufficient to explain the concurrent nitrogen isotopic anomaly and facilitate an end‐Cretaceous algae bloom.