Based on two decades of research, The Late Devonian Mass Extinction reviews the many theories that have been presented to explain the global mass extinction that struck the earth over 367 million years ago, considering in particular the possibility that the extinction was triggered by multiple impacts of extraterrestrial objects.

The primary goal of this dissertation is to increase understanding of the so-called Late Devonian mass extinction through the use of stable isotope geochemistry. Despite decades of research, the timing, cause(s), and extent of the events surrounding this devastating interval in Earth history remain poorly understood. One of the best places to study the Devonian period is the Lennard Shelf in the Canning Basin of Western Australia. This region contains extensive, well-preserved exposures of Middle and Upper Devonian (Givetian, Frasnian, and Famennian) carbonate reefal platforms and slopes that are ideal for geochemical analyses. A significant amount of information could be learned about the Late Devonian mass extinction in the Canning Basin if we had a detailed chronostratigraphic framework of platform to basin strata and a better understanding of the paleoenvironmental conditions during the Upper Devonian. This research aims to use stable isotope chemostratigraphy to help build a high resolution chronostratigraphy and examine any environmental changes leading up to and following the F-F boundary that may have contributed to Devonian extinction events in the Canning Basin. This dissertation is divided into two parts; the first concerns my research on the Late Devonian mass extinction while the second is ancillary and documents my astrobiology research rotation. Part 1 contains introductory and concluding remarks as well as three chapters written as scientific manuscripts that have been, or will soon be, submitted for journal publication. The first of these three chapters examines the local and global controls on carbon isotope chemostratigraphy in the Lennard Shelf system to validate the use of secular variations as a chronostratigraphic tool for regional and global correlations. The next chapter provides a detailed, expanded view of the F-F boundary and constrains the pattern of carbon isotope perturbations across said boundary at the intra-zonal scale. The third scientific chapter broadens focus from the F-F to the entirely of the Upper Devonian and presents the first carbon isotope composite curve from Western Australia that is used to test the global nature (timing and extent) of Late Devonian events and examine the relationship between carbon isotope fluctuations, faunal turnover, and changes in the paleoenvironment (sea level, climate, ocean chemistry, paleogeography). Results from Part 1 not only have implications for re-evaluating one of the "Big Five" mass extinctions in the Phanerozoic, but are also relevant to studies in astrobiology and have additional applications in the oil and gas industry. The final chapter of my dissertation, which is in Part 2, concerns interdisciplinary, astrobiology work done during summer quarter, 2014, that was devoted to analyzing the relationship between astronomy and geology circa 1770-1810. This chapter is included in my dissertation as partial fulfillment of my dual-title astrobiology degree.

The invasion of land by ocean-dwelling plants and animals was one of the most revolutionary events in the evolution of life on Earth, yet the animal invasion almost failed—twice—because of the twin mass extinctions of the Late Devonian Epoch. Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a blow that almost drove them back into the sea. If those extinctions had been just a bit more severe, spiders and insects—instead of vertebrates—might have become the ecologically dominant forms of animal life on land. This book examines the profound evolutionary consequences of the Late Devonian extinctions and the various theories proposed to explain their occurrence. Only one group of four-limbed vertebrates exists on Earth, while other tetrapod-like fishes are extinct. This gap is why the idea of "fish with feet" seems so peculiar to us, yet such animals were once a vital part of our world, and if the Devonian extinctions had not happened, members of these species, like the famous Acanthostega and Ichthyostega, might have continued to live in our rivers and lakes. Synthesizing decades of research and including a wealth of new discoveries, this accessible, comprehensive text explores the causes of the Devonian extinctions, the reasons vertebrates were so severely affected, and the potential evolution of the modern world if the extinctions had never taken place.

The invasion of land by ocean-dwelling plants and animals was one of the most revolutionary events in the evolution of life on Earth, yet the animal invasion almost failed—twice—because of the twin mass extinctions of the Late Devonian Epoch. Some 359 to 375 million years ago, these catastrophic events dealt our ancestors a blow that almost drove them back into the sea. If those extinctions had been just a bit more severe, spiders and insects might have become the ecologically dominant forms of animal life on land. This book examines the profound evolutionary consequences of the Late Devonian extinctions, which shaped the composition of the modern terrestrial ecosystem. Only one group of four-limbed vertebrates now live on Earth while other tetrapod-like fishes are extinct. This gap is why the idea of “fish with feet” seems so peculiar yet these animals were once a vital part of our world.

The Late Devonian and Permian-Triassic intervals are among the most dynamic episodes of Earth history, marked by large secular changes in continental ecosystems, dramatic fluctuations in ocean oxygenation, major phases of biotic turnover, volcanism, bolide impact events, and rapid fluctuations in stable isotope systems and sea level. This volume highlights contributions from a broad range of geological sub-disciplines currently striving to understand these critical intervals of geologically rapid, global-scale changes.* Provides updated, current models for the mid-Late Devonian and Permian-Triassic mass extinction episodes* Highlights several new analytical approaches for developing quantitative datasets* Takes an integrated approach presenting datasets from a broad range of sub-disciplines

Picture a world of dog-sized scorpions and millipedes as long as a car; tropical rainforests with trees towering over 150 feet into the sky and a giant polar continent five times larger than Antarctica. That world was not imaginary; it was the earth more than 300 million years ago in the Carboniferous period of the Paleozoic era. In Carboniferous Giants and Mass Extinction, George R. McGhee Jr. explores that ancient world, explaining its origins; its downfall in the end-Permian mass extinction, the greatest biodiversity crisis to occur since the evolution of animal life on Earth; and how its legacies still affect us today. McGhee investigates the consequences of the Late Paleozoic ice age in this comprehensive portrait of the effects of ancient climate change on global ecology. Carboniferous Giants and Mass Extinction examines the climatic conditions that allowed for the evolution of gigantic animals and the formation of the largest tropical rainforests ever to exist, which in time turned into the coal that made the industrial revolution possible—and fuels the engine of contemporary anthropogenic climate change. Exploring the strange and fascinating flora and fauna of the Late Paleozoic ice age world, McGhee focuses his analysis on the forces that brought this world to an abrupt and violent end. Synthesizing decades of research and new discoveries, this comprehensive book provides a wealth of insights into past and present extinction events and climate change.

"Comprises articles stemming from the March 2013 international conference at London's Natural History Museum. Researchers across geological, geophysical, and biological disciplines present key results from research concerning the causes of mass extinction events"--