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A biography and obituary of William G. Chaloner FRS (1928–2016)
Abstract
William G. (‘Bill’) Chaloner FRS (1928–2016) was one of the world’s leading palaeobotanists and palynologists. He developed a love of natural science at school which led to a penchant for palaeobotany at university. Bill graduated in 1950 from the University of Reading, and remained there for his PhD, supervised by Tom Harris, on the spores of Carboniferous lycopods. After completing his PhD in 1953, Bill undertook a postdoctoral fellowship in the USA. He returned to the UK and, in 1956, began a long and distinguished academic career at four colleges of the University of London. His first position was at University College London, where he continued to work on Paleozoic palaeobotany and palynology. His 1958 paper on the effects of fluctuating sea levels on Carboniferous pollen-spore assemblages proved highly influential. Bill moved to a Chair at Birkbeck College in 1972, began to use the scanning electron microscope and was elected a Fellow of The Royal Society in 1976. He is the only pre-Quaternary palynologist to have been given the latter honour. In 1979, Bill was appointed to the Chair of Botany at Bedford College where he began to apply plant fossil evidence to general scientific problems. He began to work on arthropod–plant interactions, fossil charcoal and growth rings in wood. Bill was awarded the Medal for Scientific Excellence by the American Association of Stratigraphic Palynologists in 1984. Bedford College and Royal Holloway College merged in 1985, and Bill moved to the amalgamated institution. Bill continued to investigate very diverse topics, and added the analysis of leaf stomata, global environmental change and molecular palaeontology to his portfolio. Following retirement in 1994, Bill continued his research and teaching at Royal Holloway, University of London. His final paper was published in 2016, bringing to an end a research career of 66 years.
... Over his career more than forty palaeobotanists and palynologists from around the world worked with him for long periods, including nearly thirty PhD and other students, postdocs, research assistants, and visiting researchers. The extent of Bill's influence, and the respect with which he was held among those who knew him, is reflected in the several tributes published in his lifetime (Collinson & Scott 1993;Traverse 1993) and since his death (Scott 2016a(Scott ,b,c, 2018aCollinson 2017;Pearson 2017;Scott & Crane 2018;Riding et al. 2020). ...
... He influenced not only their science, but also their approach to science, in which it was not only depth that was valued, but also breadth, creativity, and the importance of an open and enquiring mind. (Scott 2018b) and Fire -a very short introduction (Scott 2020). (Beerling, 2019) as well as the best-selling book The emerald planet: how plants changed Earth's history (Beerling, 2007), which formed the basis of the BBC TV series How to grow a planet. ...
William G. Chaloner, widely known as Bill, was a world leader in the study of plant fossils. He was a pioneer in the development of palaeopalynology and helped integrate studies of macroscopic plant fossils with investigations of fossil pollen and spores. His early work expanded our understanding of Carboniferous coal-forming plants and vegetation and his investigations on the changing distributions of fossil plants contributed to improved knowledge of biogeographic patterns during the late Paleozoic, including the concept of continental drift before it was widely accepted. Bill's relentless creativity demonstrated how the fossil record of plants could be exploited to reconstruct ancient climates. He also recognized that because certain structural features of fossil leaves directly record levels of the greenhouse gas carbon dioxide they are valuable ‘biosensors’ of ancient atmospheric composition allowing investigation of the link between the greenhouse effect and past warm climates. With his clear and critical mind and grasp of diverse subject matter, Bill was adept at distilling disparate information into a coherent and understandable whole. An engaging communicator, and an unfailingly supportive mentor, he inspired many young scientists during his five decades of service to colleges of the University of London.
... He rose through the ranks of academe to Reader, via Senior Lecturer. Roger immediately began to train PhD students, the first of these being Bernard Owens, extending the knowledge of the stratigraphical distribution of Carboniferous miospores (Owens 1963;Owens and Burgess 1965;Neves and Owens 1966;Riding et al. 2020). The concerted efforts to document the stratigraphical distributions of British Carboniferous miospores by several of Roger's research students led to the publication of biozonations (Neves et al. 1972(Neves et al. , 1973Owens et al. 1977) which provided a significant contribution to the enduring standard zonal scheme of Clayton et al. (1977). ...
This paper reviews climate and vegetation history for tropical Asia for the last three million years prior to the Holocene, comparing the history for India and Southeast Asia for the later Pliocene, and Pleistocene, paying emphasis to the last glacial maximum. The Pliocene witnessed the demise of humid tropical forests across India, which were replaced at least in the north by open grasslands, which supported a diverse fauna, elements of which migrated to Java during the Early Pleistocene. The suggestion that the fauna migrated along a “savanna corridor” is dismissed since although there are many semi-evergreen Indochinese plant taxa in Java, there are no representatives of Indochinese deciduous forests, suggesting that there may have been a corridor of semi-evergreen forests, but not deciduous forests or savanna. During Pleistocene glaciations, there was an expansion of desert and savanna vegetation at the expense of deciduous and evergreen forests across the Indian subcontinent, whereas in Southeast Asia, rain forests remained along the equator, with fire-climax pine forest at northern subequatorial latitudes, followed by savanna to the north in Indochina, but with the expansion of seasonal evergreen and deciduous forests to the south, across the emergent Java Sea and Java. It is suggested that widespread Pleistocene megafauna may have considerably modified vegetation across the region compared to today.
Keywords: Marine palynology; Savanna corridor; Homo erectus; Homo sapiens; Last glacial maximum; Megafauna; Sequence-biostratigraphy
Obituary for Professor Bernard Owens.
The Brassington Formation of the Pennines is the most extensive onshore Miocene succession in the UK. It is preserved as outliers in Lower Carboniferous Limestone. During the Cenozoic, central England underwent uplift, with erosion of post-Mississippian strata from the Pennine axis in the Peak District. The Brassington Formation is hence significant in reconstructing Cenozoic geological history. It is non-marine, derived from Triassic sandstone and of Mid–Late Miocene age. The c. 60 outliers occur in three clusters over c. 220 km². They are remnants of a sedimentary prism at least 75 m thick and with a volume of c. 10 km³. Suffosion of bedrock, conditioned by aggressive precursor fluids of hypogenic origin, was the major control on subsidence. The calculated volume of the fills in the Bees Nest and Green Clay outliers is 3.7–5.0 × 10⁶ m³. Referenced to a sub-Miocene surface at c. 450 m OD in pre-subsidence times, the original volume of this subsidence complex was c. 21.8 × 10⁶ m³ and the aggregated volume of the Late Neogene White Peak palaeokarst was at least 0.66 km³. Subsidence was concomitant with Pliocene uplift of the Pennine Axis, suggesting suffosion accommodation of 3 × 10⁶ m³ per km² or 244 m³ per annum.
Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angiosperms is still uncertain. Here we report model-based reconstructions for ancestral flowers at the deepest nodes in the phylogeny of angiosperms, using the largest data set of floral traits ever assembled. We reconstruct the ancestral angiosperm flower as bisexual and radially symmetric , with more than two whorls of three separate perianth organs each (undifferentiated tepals), more than two whorls of three separate stamens each, and more than five spirally arranged separate carpels. Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms.
The Brassington Formation is the most extensive Miocene sedimentary succession onshore in the UK. Because of its unique position at the margin of NW Europe, the pollen from this lithostratigraphical unit provides evidence on the development of vegetation affected by North Atlantic currents and hypothesized atmospheric circulation changes during the Middle to Late Miocene climate cooling. Palynostratigraphy suggests that the uppermost Kenslow Member of the Brassington Formation is not coeval. Previously, all occurrences of the Kenslow Member were assumed to be contemporary. The oldest pollen assemblage is from the more southern Bees Nest Pit, which represents a subtropical conifer-dominated forest of late Serravallian age (c. 12 Ma). A younger assemblage was observed from the more northern Kenslow Top Pit; this indicates that a subtropical mixed forest was present during the early Tortonian (11.6–9 Ma). The shift from a conifer-dominated to a mixed forest was related to precipitation. Although the total precipitation did not change between the two assemblages, the younger assemblage had more uniform rainfall throughout the year. The diachronous nature of the Kenslow Member means that the depositional model of the Brassington Formation needs revising, and this will have implications for Neogene to recent uplift of the southern Pennines.
Fire has been an important part of the Earth system for over 350 Myr. Humans evolved in this fiery world and are the only animals to have used and controlled fire. The interaction of mankind with fire is a complex one, with both positive and negative aspects. Humans have long used fire for heating, cooking, landscape management and agriculture, as well as for pyrotechnologies and in industrial processes over more recent centuries. Many landscapes need fire but population expansion into wildland areas creates a tension between different interest groups. Extinguishing wildfires may not always be the correct solution. A combination of factors, including the problem of invasive plants, landscape change, climate change, population growth, human health, economic, social and cultural attitudes that may be transnational make a re-evaluation of fire and mankind necessary. The Royal Society meeting on Fire and mankind was held to address these issues and the results of these deliberations are published in this volume.
This article is part of the themed issue ‘The interaction of fire and mankind’.
Living with fire is a challenge for human communities because they are influenced by socio-economic, political, ecological and climatic processes at various spatial and temporal scales. Over the course of 2 days, the authors discussed how communities could live with fire challenges at local, national and transnational scales. Exploiting our diverse, international and interdisciplinary expertise, we outline generalizable properties of fire-adaptive communities in varied settings where cultural knowledge of fire is rich and diverse. At the national scale, we discussed policy and management challenges for countries that have diminishing fire knowledge, but for whom global climate change will bring new fire problems. Finally, we assessed major fire challenges that transcend national political boundaries, including the health burden of smoke plumes and the climate consequences of wildfires. It is clear that to best address the broad range of fire problems, a holistic wildfire scholarship must develop common agreement in working terms and build across disciplines. We must also communicate our understanding of fire and its importance to the media, politicians and the general public.
This article is part of the themed issue ‘The interaction of fire and mankind’.
Al and Betty Traverse in the Botanischer Garten , Berlin, Germany in August 1987.
Professor Alfred (‘Al’) Traverse passed away following a long illness at 90 years of age on September 15th 2015 at Juniper Village, State College, Pennsylvania, USA. With his death, the twin sciences of palaeobotany and palynology have lost one of their most influential and productive of practitioners and teachers. He had a stellar student career, was a coal petrologist, an industrial palynologist and held parallel positions in the Episcopal (Anglican) church. However he is principally defined by his 30-year tenure as a professor at The Pennsylvania State University (Penn State) from 1966 to his full retirement in 1996. Al was an incredibly diverse scientist; the topics of his numerous research papers are highly eclectic. He demonstrated a truly polymathic approach to palaeobotany and palynology. Most notably, he published two editions of the only single-author textbook ever published in English on pre-Quaternary palynology. This short article seeks to celebrate and document Al’s fascinating, fulfilling, long and productive life, hence it is designated as both a biography and an obituary. The authors have drawn on their collective memories, Al’s publications, online information and other obituaries such as Anonymous (2015) and Rich & Strother (2015).
Alfred Traverse was born on the 7th of September (Labor Day) 1925 at St. James Anglican rectory in Port Hill, Prince Edward Island, Canada. He was always known as Al to everyone, and was the son of the Reverend A. Freeman Traverse, a priest in the Episcopal church. His mother was Pearle Akerley Traverse, who was a dietician and schoolteacher. In 1926 the Traverse family moved to Lucknow in southern Ontario, and then to Allegan, Michigan, USA in 1928. Al never moved back to Canada, and he became a naturalised United …
Pollen and spores are ubiquitous, and preserve exceptionally well. This, with their great structural diversity, offers exceptional opportunities for integrating findings from studies of both recent and fossil material, and for developing new insights into pathways and processes of diversification. This volume brings together novel approaches from such diverse fields as palaeobotany, ontogeny, molecular biology, and systematics. Three main issues are discussed: the evidence provided by the fossil record, the contribution of ontogenetic data, and methods of systematic analysis. The information provided will be of great interest and relevance to such disparate disciplines as vegetational history, geology, plant taxonomy, and plant evolution.
Introduction
In the Mediterranean region, several studies have been devoted to the distribution of pollen in coastal marine areas (Rossignol, 1961; Koreneva, 1971; Rossignol & Pastouret, 1971; Belfiore et al., 1981; Brun, 1983). Other studies have tried to understand the pollen rain in mountain areas where peat bogs are excellent pollen recorders (Reille, 1975; Beaulieu, 1977). However, little is known about how much of the pollen produced in high and middle altitudes is transported to the area of sedimentation near the shoreline, and how it is transported.
The region of Calvi in Corsica is typical of Mediterranean climatic conditions, where mountains rise to 2000 m a short distance (20 km) from the coast, with rather humid climate at the top (near 2000 mm precipitation, concentrated during the cold season; Simi, 1964), and rather dry climate (near 700 mm precipitation) near the coast. Autumn, winter, or spring high rainfall on the top and on steep slopes (Fig. 5.1) produces huge and violent floods (Guilcher, 1979), which carry large stones that accumulate on the narrow coastal plain and which also deliver fine material to the sea. During the dry season (summer) the rivers are at minimum flow and often vanish in the coarse sediments of the coastal plain. Two small rivers enter the sea near Calvi, the Fiume Secco and the Ficarella (Fig. 5.1).
Raging wildfires have devastated vast areas of California and Australia in recent years, and predictions are that we will see more of the same in coming years, as a result of climate change. But this is nothing new. Since the dawn of life on land, large-scale fires have played their part in shaping life on Earth.
Andrew Scott tells the whole story of fire's impact on our planet's atmosphere, climate, vegetation, ecology, and the evolution of plant and animal life. It has caused mass extinctions, and it has propelled the spread of flowering plants.
The exciting evidence we can now draw on has been preserved in fossilized charcoal, found in rocks hundreds of millions of years old, from all over the world. These reveal incredibly fine details of prehistoric plants, and tell us about climates from deep in earth's history. They also give us insight into how early hominids and humans tamed fire and used it.
Looking at the impact of wildfires in our own time, Scott also looks forward to how we might better manage them in future, as climate change has an increasing effect on our world.
This volume is a collection of papers presented to Professor Tom Barnard by former students, colleagues and friends to mark thirty-two years of teaching and research in micropalaeontology at University College London. This period represents the major part of Tom Barnard's career with microfossils, which actually began rather earlier, but in 1949 his first postgraduate students were registered. Since then some 150 students have worked for higher degrees studying foraminifera, ostracods, calcareous nannofossils, dino of Research flagellates and palynomorphs, in company with a series Assistants and Visiting Scientists. The nature of micropalaeontology at 'UC' under Tom Barnard has always been unashamedly biostratigraphical. As a result many students have entered and continue to enter the petroleum industry, not least of all because their mentor has always had a pragmatic view of academic research and its direction. Despite this emphasis, with a particular attention to Mesozoic foraminifera, a major investigation of Recent Caribbean foraminiferal faunas has been carried out and most recently MSc classes have worked with material from the continental shelf of southern Africa. Work with Mesozoic ostracods was initiated in 1956 and during the past decade a growing number of students have concentrated on calcareous nannofossils. A book sum marising the results of biostratigraphical work with nannofossils is at present in the press (Lord, A. R. (ed. ) A stratigraphical index of calcareous nanno fossils. Chichester: Ellis Horwood).
Occasionally (and fortunately), circumstances and timing combine to allow an individual, almost singlehandedly, to generate a paradigm shift in his or her chosen field of inquiry. William R. (Bill) Evitt (1923-2009) was such a person. During his career as a palaeontologist, Bill Evitt made lasting and profound contributions to the study of both dinoflagellates and trilobites. He had a distinguished, long and varied career, researching first trilobites and techniques in palaeontology before moving on to marine palynomorphs. Bill is undoubtedly best known for his work on dinoflagellates, especially their resting cysts. He worked at three major US universities and spent a highly significant period in the oil industry. Bill's early profound interest in the natural sciences was actively encouraged both by his parents and at school. His alma mater was Johns Hopkins University where, commencing in 1940, he studied chemistry and geology as an undergraduate. He quickly developed a strong vocation in the earth sciences, and became fascinated by the fossiliferous Lower Palaeozoic strata of the northwestern United States. Bill commenced a PhD project on silicified Middle Ordovician trilobites from Virginia in 1943. His doctoral research was interrupted by military service during World War II; Bill served as an aerial photograph interpreter in China in 1944 and 1945, and received the Bronze Star for his excellent work. Upon demobilisation from the US Army Air Force, he resumed work on his PhD and was given significant teaching duties at Johns Hopkins, which he thoroughly enjoyed. He accepted his first professional position, as an instructor in sedimentary geology, at the University of Rochester in late 1948. Here Bill supervised his first two graduate students, and shared a great cameraderie with a highly motivated student body which largely comprised World War II veterans. At Rochester, Bill continued his trilobite research, and was the editor of the Journal of Paleontology between 1953 and 1956. Seeking a new challenge, he joined the Carter Oil Company in Tulsa, Oklahoma, during 1956. This brought about an irrevocable realignment of his research interests from trilobites to marine palynology. He undertook basic research on aquatic palynomorphs in a very well-resourced laboratory under the direction of one of his most influential mentors, William S. Bill Hoffmeister. Bill Evitt visited the influential European palynologists Georges Deflandre and Alfred Eisenack during late 1959 and, while in Tulsa, first developed several groundbreaking hypotheses. He soon realised that the distinctive morphology of certain fossil dinoflagellates, notably the archaeopyle, meant that they represent the resting cyst stage of the life cycle. The archaeopyle clearly allows the excystment of the cell contents, and comprises one or more plate areas. Bill also concluded that spine-bearing palynomorphs, then called hystrichospheres, could be divided into two groups. The largely Palaeozoic spine-bearing palynomorphs are of uncertain biological affinity, and these were termed acritarchs. Moreover, he determined that unequivocal dinoflagellate cysts are all Mesozoic or younger, and that the fossil record of dinoflagellates is highly selective. Bill was always an academic at heart and he joined Stanford University in 1962, where he remained until retiring in 1988. Bill enjoyed getting back into teaching after his six years in industry. During his 26-year tenure at Stanford, Bill continued to revolutionise our understanding of dinoflagellate cysts. He produced many highly influential papers and two major textbooks. The highlights include defining the acritarchs and comprehensively documenting the archaeopyle, together with highly detailed work on the morphology of Nannoceratopsis and Palaeoperidinium pyrophorum using the scanning electron microscope. Bill supervised 11 graduate students while at Stanford University. He organised the Penrose Conference on Modern and Fossil Dinoflagellates in 1978, which was so successful that similar meetings have been held about every four years since that inaugural symposium. Bill also taught many short courses on dinoflagellate cysts aimed at the professional community. Unlike many eminent geologists, Bill actually retired from actively working in the earth sciences. His full retirement was in 1988; after this he worked on only a small number of dinoflagellate cyst projects, including an extensive paper on the genus Palaeoperidinium. © 2016 National Environment Research Council (NERC)-British Geological Survey (BGS).
The term “spore” has been applied to single-celled and small multi-cellular propagules from a wide range of organisms. When the cell walls of these spores are encountered as fossils, there is no secure criterion of morphology for separating all algal spores from those of all vascular plants; nor of separating all pollen grains from micro- and isospores of vascular plants. The application of the term sporopollenin not merely to all these spores and pollen grains but also to kerogen and organic material in meteorites is questionable because of the biological origin implicit in the term. We need to know whether fossil organic matter other than spore and pollen exines has similar - or distinct - physico-chemical characteristics. Fossil spore wall material from diverse sources shows minor differences in physical properties such as specific gravity. Flotation on a density gradient may be one means of segregating such spores when differences of morphology alone are not sufficiently characteristic.
The conventional approach to Tertiary palaeobotany and the analysis of the climatic implications of floristic change is based on an assumption of relative stability of the taxon/climate relationship. The observed pattern of migration of land plant taxa has largely overshadowed the recognition of changes which may have accompanied migration, in species tolerance and in the phenotypic response of plant structure to environmental constraints. Some features of plants are tightly controlled by the genotype (i.e. are conservative), while others are less so, and in that sense are designated as showing phenotypic plasticity. A series of morphological features of plants (the width and character of growth rings in wood, leaf physiognomy and stomatal density) range from being conservative to plastic in the response that they show to environmental change. The nature of the response (both immediate, phenotypic and gradual genotypic evolutionary adaptation) is reviewed.
In characterizing Chester A. Arnold, the single word that best describes both the man and the scientist is substantial. He was substantial in appearance-a tall, large man whose presence was always felt despite his reticence. His physical size was exceeded by the stature of his contributions to paleobotany; his interests ranged from the Paleozoic to the Tertiary. His impacts upon his colleagues and students were substantive-his terse, measured comments always impaled the moment. Arnold played a critical role in the growth of paleobotany into a major discipline in the United States by way of his introductory textbook on paleobotany (1947) and his numerous fundamental paleobotanical contributions, mainly on Devonian, Mississippian, and Pennsylvanian floras. Arnold was honored by his receipt of the Silver Medal of the Birbal Sahni Institute of Paleobotany (India) and of the Distinguished Service Award of the Paleobotanical Section of the Botanical Society of America and by the naming of several paleobotanical taxa for him.
Marie Charlotte Carmichael Stopes was one of the most remarkable women of the twentieth century. She will be remembered more for her work in pioneering the defense of women's rights and birth control than for her contributions to paleobotany. Three aspects of her research on fossil plants are relevant to the development of that subject in North America; her revision of the Carboniferous "Fern Ledges" flora of New Brunswick, Canada; her work on the origin of coal balls; and her studies on coal petrology.
Mathematical representations of the cellular organization and dimensions of Spongiophyton Krausel, a Middle Devonian thallophyte were projected by means of a computer to simulate patterns of development and organization. Extrapolation of the cellular patterns observed on the surface of the fossil may be compared with those derived from living plants of which the ontogeny can be directly observed. Spongiophyton is compared in this respect with the growth of Protosalvinia (an Upper Devonian plant of enigmatic affinity), Pellia (a thallose liverwort) and Cutleria (a brown alga). The growth pattern of Spongiophyton developed by computer shows a closer similarity to that of the pseudoparenchymatous alga Cutleria than to the truly parenchymatous Pellia or the fossil Protosalvinia. Computer simulations of the growth process throw light on the affinity of Spongiophyton which cannot be derived from direct observation of the fossil. Broader applications of computer simulations of tissue organization and gross morphology are suggested with regard to the study of living and fossil plants.
A new type of fossil spore tetrad, Didymosporites scotti gen. et sp. nov. is described from the Dinantian and Namurian (Carboniferous) of Ireland, Scotland, and England. The spores always occur in the form of a tetrad composed of two large (presumably fertile) and two minute (presumably abortive) spores, all with cutinized walls. Reasons are given for regarding these as the megaspores of the coenopterid fern Stauropteris burntislandica; their distribution indicates a far wider range in time and space than that previously known for this species. Their occurrence as adhering tetrads suggests that Stauropteris burntislandica 'shed' its megaspores still enclosed in the sporangiumIan interesting analogy with both Lepidocarpon and the seeds of Pteridosperms.
Preface to Vegetation-climate-atmosphere interactions: past, present and future, the proceedings of a Discussion Meeting held at the Royal Society. Organized and edited by D. J. Beerling, W. G. Chaloner and F. I. Woodward.
The contributions of James (Jim) M. Schopf (1911-1978) to the development of upper Carboniferous and Permian paleobotany, palynology, and coal geology are among the most influential of the mid-twentieth century. Jim's scientific endeavors reached far beyond this scope and extended from the Precambrian to the Pleistocene. His research papers provided many of the integrated benchmarks upon which his and subsequent generations have built. Jim Schopf was respected for his rigorous standards of scholarship and for his candor. He was also one of our most generous and helpful colleagues, and his wise counsel aided many. His graduate studies at the University of Illinois, Urbana, overlapped with pioneering research in the Coal Division, Illinois State Geological Survey (1934-1943). He served with the U.S. Bureau of Mines at Pittsburgh (1943-1947) and the U.S. Geological Survey (1947-1978). In 1949, Jim Schopf established the Coal Geology Laboratory at Ohio State University, Columbus, which became an important center for coal research and scientific exchange- and a special attraction for visiting paleobotanists, palynologists, and coal geologists. The Schopf home was also noted for its gracious hospitality and lively discussions of current research issues. Schopf was especially known as a gregarious and ardent "field tripper," one with a remarkable ability to discover fossil-plant deposits. One of his special challenges was the paleobotany of the Antarctic (1960-1978), in cooperation with the Institute of Polar Studies at Ohio State University. He received many honors, including the Gilbert H. Cady Award of the Coal Geology Division of the Geological Society of America, Mary Clark Thompson Medal of the National Academy of Sciences, and the Paleontological Society Medal. Mt. Schopf in Antarctica was named in honor of his contributions to Antarctic science.
Charcoal is produced by pyrolysis of plant material and its occurrence in the fossil record can be broadly equated with the incidence of palaeowildfire. The past record of such naturally occurring fire, and tha availability of the biomass which represents its fuel, put two constraints on oxygen levels. For combustion of plant material to occur at all requires that the atmospheric oxygen did not drop below a threshold of 13%. Increasing inflammability of plant material at higher oxygen levels suggests that 35% would be a ceiling above which plant biomass would ignite and burn so readily as to be incompatible with sustained forest growth. As we have more or less continuous fossil evidence of forest trees from the Late Devonian onwards, and a similarly sustained record of fossil charcoal from that time to the present (Cope, 1984), this constraints oxygen levels between 13% and 35% over that period (Rabash and Langford, 1968; Watson et al., 1978). However, further experimental work is required to establish the validity of these oxygen values under appropriate conditions and also to sharpen the certainty by which we can discriminate between fusain produced by pyrolysis, and inert wood degradation products produced by other (? biogenic) means. We discuss experiments directed at attempting to establish the validity of physical parameters by which pyrolytically produced fusain can be characterized. The most convincing evidence of pyrolysis hitherto recognised is the apparent homogenization of xylem cell walls, as seen under SEM. Work on charcoal from both wildfires and laboratory wood charring under controlled conditions confirms the homogenization as seen under both SEM and TEM. Controlled temperature experiments show that a further rise in temperature causes the cell walls, initially homogenized, to crack and separate along the site of the middle lamella, giving the charcoal a characteristic fibrous texture. Both of these distinctive phases of response to pyrolysis can be observed in fossil charcoals.
