Event stratigraphy is used to help characterise the Anthropocene as a chronostratigraphic concept, based on analogous deep-time events, for which we provide a novel categorization. Events in stratigraphy are distinct from extensive, time-transgressive 'episodes' – such as the global, highly diachronous record of anthropogenic change, termed here an Anthropogenic Modification Episode (AME). Nested within the AME are many geologically correlatable events, the most notable being those of the Great Acceleration Event Array (GAEA). This isochronous array of anthropogenic signals represents brief, unique events evident in geological deposits, e.g.: onset of the radionuclide 'bomb-spike'; appearance of novel organic chemicals and fuel ash particles; marked changes in patterns of sedimentary deposition, heavy metal contents and carbon/nitrogen isotopic ratios; and ecosystem changes leaving a global fossil record; all around the mid-20th century. The GAEA reflects a fundamental transition of the Earth System to a new state in which many parameters now lie beyond the range of Holocene variability. Globally near-instantaneous events can provide robust primary guides for chronostratigraphic boundaries. Given the intensity, magnitude, planetary significance and global isochroneity of the GAEA, it provides a suitable level for recognition of the base of the Anthropocene as a series/epoch.
We synthesize research from complementary scientific fields to address the likely extent and duration of the proposed Anthropocene epoch. Ongoing intensification of human-forced climate change began in the mid-20th century, with steepening increases in greenhouse gases, ocean acidification, global temperature and sea level, along with the restructuring of Earth's biota. The resulting distinction between relatively stable Holocene conditions and those of the proposed Anthropocene epoch is substantial, irreversible, and likely to persist indefinitely. The still-rising trajectory of greenhouse gas emissions from the energy requirements of a growing global population is leading to yet greater and more permanent divergence of the Anthropocene from the Holocene Earth System. We focus here on the effects of the ensuing climate transformation and its impact on the likely duration of this novel state of the Earth System. Given the magnitude and rapid rise of atmospheric carbon dioxide (CO2), its long lifetime in the atmosphere, and the present disequilibrium in Earth's energy budget (expressed as the Earth's Energy Imbalance, or EEI), both temperatures and sea level must continue to rise – even if carbon emissions were lowered to net zero (where CO2 emissions = CO2 removals) – until the energy budget balance is eventually restored. Even if net zero were achieved immediately, elevated global temperatures would persist for at least several tens of millennia. The expected levels of warmth have not been seen since the early Late Pliocene, and interglacial conditions are likely to persist for at least 50,000 years from now under already-accumulated CO2 emissions and Earth's low eccentricity orbit. Continued increases in greenhouse gas emissions are likely to extend that persistence to around 500,000 years and will likely suppress the pronounced expression of Milankovitch cyclicity typical of the Pleistocene Epoch. This major perturbation alone is sufficient to justify the Anthropocene as an epoch terminating the Holocene Epoch; the wider effects of climate change in driving further, mostly irreversible, restructuring of the biosphere amplifies this distinction.
Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene.
One of the great debates about extinction is whether humans or climatic change caused the demise of the Pleistocene megafauna. Evidence from paleontology, climatology, archaeology, and ecology now supports the idea that humans contributed to extinction on some continents, but human hunting was not solely responsible for the pattern of extinction everywhere. Instead, evidence suggests that the intersection of human impacts with pronounced climatic change drove the precise timing and geography of extinction in the Northern Hemisphere. The story from the Southern Hemisphere is still unfolding. New evidence from Australia supports the view that humans helped cause extinctions there, but the correlation with climate is weak or contested. Firmer chronologies, more realistic ecological models, and regional paleoecological insights still are needed to understand details of the worldwide extinction pattern and the population dynamics of the species involved.
The "Great Acceleration" of the mid-20th century provides the causal mechanism of the Anthropocene, which has been proposed as a new epoch of geological time beginning in 1952 CE. Here we identify key parameters and their diagnostic palaeontological signals of the Anthropocene, including the rapid breakdown of discrete biogeographical ranges for marine and terrestrial species, rapid changes to ecologies resulting from climate change and ecological degradation, the spread of exotic foodstuffs beyond their ecological range, and the accumulation of reconfigured forest materials such as medium density fibreboard (MDF) all being symptoms of the Great Acceleration. We show: 1) how Anthropocene successions in North America, South America, Africa, Oceania, Europe, and Asia can be correlated using palaeontological signatures of highly invasive species and changes to ecologies that demonstrate the growing interconnectivity of human systems; 2) how the unique depositional settings of landfills may concentrate the remains of organisms far beyond their geographical range of environmental tolerance; and 3) how a range of settings may preserve a long-lived, unique palaeontological record within post-mid-20th century deposits. Collectively these changes provide a global palaeontological signature that is distinct from all past records of deep-time biotic change, including those of the Holocene.
PALAEOECOLOGY AND PALAEOENVIRONMENTS OF LATE CEN‐OZOIC MAMMALS. TRIBUTES TO THE CAREER OF C. S. (RUFUS) CHURCHER, edited by Kathlyn M. Stewart and Kevin L. Seymour, 1996. University of Toronto Press, Toronto, 675 pp. ISBN 0–002–0072–87. Price US $75. EVOLUTION AND ECOLOGY; THE PACE OF LIFE, by K. D. Bennett, 1997. Cambridge University Press, Cambridge, England, 241 p. ISBN 0 521 39921 1 (paperback), price £16.95 or US$24.95; and ISBN 0 521 39028 1 (hardback), price £50.00 or US$69.95. THE MOLECULAR BIOLOGY OF GAIA, by George R. Williams, 1997. Columbia University Press, New York. ISBN 0–231–10512–6. Price: $52.00 (cloth). RICHARDSON'S GUIDE TO THE FOSSIL FAUNA OF MAZON CREEK, edited by Charles W. Shabica and Andrew A. Hay, 1997. Northeastern Illinois University, Chicago, xvi + 308 p. ISBN 0–925065–21–8, price US$95.00.
Abstract The Colter Formation, composed largely of pyroclastic flow, lahar, surge, and coarse air-fall deposits, provides evidence that volcanoes were active in Jackson Hole, Wyoming, from the early to middle Miocene (late-early Arikareean to late Barstovian land-mammal age, correlating with about 24 to 13 my ago). The formation is the only record of relatively continuous early and middle Miocene volcanism known from the northern Rocky Mountains. The distribution of the Colter, its varying thickness, and facies changes within it suggest that most vents were located in the vicinity of the presently active Teton Fault. An early episode of compressional-type volcanism, lasting from at least 24 to 18 my ago, is inferred from the lower 500 m of andesitic, trachytic, and latitic tuff and ignimbrite, which are newly defined as the Crater Tuff-breccia Member. Extensional-type volcanism apparently followed by 13 my ago, as interpreted from the overlying 1000 m of rhyolitic tuff, ignimbrite, and conglomerate, the Pilgrim Conglomerate Member. The change from regional compression to extension between 18 and 13 my ago coincides with the development of the Mid-Tertiary unconformity in the northern Rockies, but the unconformity is less prominent in Jackson Hole than in southwestern Montana. The more complete depositional sequence in Jackson Hole probably is due to proximity of volcanoes that produced abundant detritus. Downfaulting, possibly as the magma chamber emptied, preserved the section. Additional movements along the Teton Fault since about 9.4 my ago tilted the Colter Formation westward and stepfaulted it into at least three major blocks that dropped eastward up to 1000 m per block.
Most species on planet Earth have specific ecological ranges. In the near surface of the oceans, planktonic foraminifera define water masses that are warm in the tropics, and cold in polar regions. Tropical rainforests have trees and animals that are distinct from those in warm temperate or cold temperate zones. The fauna and flora of Australia are distinct from those of the Americas. These natural patterns, defined by factors such as latitudinal changes in surface temperature and rainfall, or geographical isolation, have evolved over millions, sometimes tens of millions of years. Now this natural pattern is being overprinted by the actions of a single species, Homo sapiens , which has made the whole Earth its ecological range, and some parts of nearby space too. The human ancestral pattern of gradually increasing impact on the Earth can be traced in the stratigraphic record for nearly 3 million years, and in its later and more pervasive phases may serve to help define a biostratigraphical signal for the Anthropocene Epoch.
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