Charles L. Drake

Terminal cretaceous environmental events.

The geologic record of terminal Cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10,000 to 100,000 years. The available geologic evidence favors a mantle rather than meteoritic origin for these elements. These results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event.

The Cretaceous-Tertiary Transition

The fossil sequences from cores across the Cretaceous-Tertiary boundary show a, range of transition times and transition time intervals depending on the fossil indicators and the location of the site. These variations, together with the pattern of iridium distribution with depth at some sites, differences in total amounts of iridium, variations in noble metal abundances normalized to extraterrestrial concentrations, the depositional effects that might be expected in a reducing environment, and the clay mineralogy of the boundary layer clays, put into question the interpretation that an extraterrestrial event was the cause of the faunal changes and the iridium anomaly in the vicinity of the Cretaceous-Tertiary transition. It seems more likely that an explanation for the changes during the transition will come from continued examination of the great variety of terrestrial events that took place at that time, including extensive volcanism, major regression of the sea from the land, geochemical changes, and paleoclimatic and paleoceanographic changes.

The Earth and Planetary Sciences

During the last two decades the earth sciences community has become persuaded that the earth is a dynamic body; an engine driven by its internal heat. The major surface manifestation of this dynamism has been fragmentation of the earths outer shell and subsequent relative horizontal movement of the pieces on a large scale. The driving force is convection within the earth, but much remains to be learned about the nature of the convection and the composition of the earths interior. The other terrestrial planets show evidence of once having been hot, but their surfaces suggest long-term stability and lack evidence of continuing convection.

Dynamic deformation of quartz and feldspar: clues to causes of some natural crises

Abstract Indications of natural catastrophes and crises are preserved in some geologic strutures and in the stratigraphic record, emphasizing the dynamic nature of the Earths evolution. The crises may result either from exogenic or endogenic energy sources. Distinguishing between these sources is a complex, multidisciplinary problem in the Earth sciences. Shock deformation by impact has been well-studied both in shock recovery experiments and in known impactites, but only recently has the possibility of generation of shock waves by high-temperature internal explosions been seriously considered. An optically based reconaissance survey of microstructures in quartz and feldspar in some explosive silicic volcanics suggests that they may have been induced by dynamic deformation at high temperature; in some respects the character of the microstructures differs greatly from those induced by room temperature shock, whereas in others the differences are subtle. Results from recent shock recovery experiments on quartzite preheated to 440 ° and shocked to 28 GPa support this contention. For two classic Cretaceous/Tertiary sections at Gubbio, Italy, it is shown that shock mosaicism and shock lamellae occur over a 4 m interval, bisected by the boundary, in a pattern approximately correlatable with an independently established iridium enrichment. These data are incompatible with any single event and are most plausibly interpreted as reflecting a period (∼ 0.5 my) of intense, probably episodic, volcanism with a culmination at the K/T transition. Multiple dynamic events may also account for macroscopic and microscopic structures developed during the evolution of the Vredefort structure, South Africa.

Geology in China

During the International Geological Congress in Sydney, Australia, August 1977, The People9s Republic of China (PRC) was admitted to membership in the International Union of Geological Sciences, and the way was open for earth scientists in China to take part in international activities sponsored by the IUGS and its affiliated and associated organizations for the first time since 1949. To understand better how they might take part in some of these activities, the Geological Society of. China invited the President of IUGS, Professor Rudolph Trumpy to lead a mission to visit China for a month and to explain to them how international research was organized and how they might participate. The mission represented IUGS and its Commissions and Committees; International Geological Congress, Commission for the Geological Map of the World, the International Geological Correlation Programme, International Geodynamics Project, and it included the Geological Society of London, and the Geological Society of. America. It soon became apparent that to understand the activities in the geological sciences in the PRC. now and in the past, one must view them in the context of the political climate and bureaucratic fashions, a phenomenon not completely unknown to us in the West. Thus there have been peaks and valleys in geological activity that correspond to the current political philosophy.

Cretaceous/Tertiary extinctions we know the answer, but what is the question?

Much progress has been made in our understanding of the Cretaceous/Tertiary (K/T) and other extinction events throughout Phanerozoic time. Scenarios for the K/T extinctions have been outlined. Suggested exogenic causes include a large asteroid impact or a number of smaller impacts over a year or soon both continental and oceanic terranes, or a comet shower of six to ten impacts over a 1- to 3-m.y. period. Suggested endogenic causes include the environmental effects of a major sea level regression and intense global volcanism.

Gravitational circulation in the upper mantle: Implications for crustal and mantle evolution

Abstract Officer and Drake (1983) have given an quantitative description of upper mantle convection and related plate dynamics in which the principal driving force is the longitudinal density gradient within the upper mantle between the spreading ridge and the subduction zone. The principal objective, here, is to consider an additional component of flow in the upper mantle between the warmer and less dense spreading ridge and the cooler and more dense deep continental regions.

The President's Page: Building the Geodynamics Project

The President of the American Geophysical Union from 1948 to 1953 specialized in zoology as an undergraduate and received his doctorate in paleontology, although he is best known for his work in sedimentation and structural geology. Perhaps the election of a man with this background was a harbinger of things to come, since recent findings in geology and geophysics have led to a model of the earth in which it is apparent that the data from seismology, paleontology, paleomagnetism, sedimentology, geochemistry, structural geology, and other subdisciplines of the earth sciences are related in a very intimate way. Before his death in 1965 this man, Walter Bucher, wrote a paper entitled ‘The Third Confrontation’ in which he recognized that the earth sciences were in for a major upheaval. Bucher noted that twice before there had been major confrontations between geologists and geophysicists. The first, in 1899, came when Kelvin estimated the age of the earth to be between 20 and 40 m.y., a concept that was distressing to geologists and paleontologists. The second, early in this century, concerned the origin of ocean basins, which, in the eyes of the foremost geologists of the day, were sunken or collapsed continents. This concept was geophysically unappealing.