Late Frasnian–Famennian Climates Based on Palynomorph Analyses and the Question of the Late Devonian Glaciations

Earth-Science Reviews 52Ž. 2000 121±173 www.elsevier.comrlocaterearscirev

Late Frasnian±Famennian climates based on palynomorph analyses and the question of the Late Devonian glaciations Maurice Streel a,), MarioÂÂ V. Caputo b, Stanislas Loboziak c, Jose Henrique G. Melo d a UniÕersiteÂÁ de Liege, SerÕices associes Â de Paleontologie, Â Paleobotanique Â et Paleopalynologie, Â Sart-Tilman Bat.ÃÁ B 18, B-4000 Liege, Belgium b UniÕersidade Federal do Para,ÂÂÂÂ Centro de Geologia, Campus UniÕersitario do Guama, AÕ. Perimetral SrN, Belem-PA, Brazil c U.S.T.L. UPRESA 8014 du C.N.R.S., Sciences de la Terre, F-59655, VilleneuÕe d'Ascq Cedex, France d PetrobrasÂÄrCenpesrDiÕexrSebipe, Cid. UniÕ., I. Fundao, 21949-900 Rio de Janeiro, RJ, Brazil Received 9 February 2000; accepted 27 July 2000

Abstract

Palynomorph distribution in Euramerica and western Gondwana, from the Latest Givetian to the Latest Famennian, may be explained, to some extent, by climatic changes. Detailed miospore stratigraphy dates accurately the successive steps of these changes. Interpretation is built on three postulates which are discussed: Euramerica at slightly lower latitudes than generally accepted by most paleomagnetic reconstructions; a conodont time-scale accepted as the most used available subdivision of time; and Late Devonian sea-level fluctuations mainly governed by glacio-eustasy. The Frasnian±Famennian timescale is also evaluated. The comparison, based on conodont correlations, between Givetian and most of the Frasnian miospore assemblages from, respectively, northern and southern Euramerica demonstrates a high taxonomic diversity in the equatorial belt and much difference between supposed equatorial andŽ. sub tropical vegetations. On the contrary, a similar vegetation pattern and therefore probably compatible climatic conditions were present from tropical to subpolar areas. A rather hot climate culminated during the Latest Frasnian when equatorial miospore assemblages reached their maximum width. The miospore diversity shows also a rather clear global Late Frasnian minimum which is also recorded during the Early and Middle Famennian but only in low latitude regions while, in high latitude, very cold climates without perennial snow may explain the scarcity of miospores and so, of vegetation. The Early and Middle Famennian conspicuous latitudinal gradient of the vegetation seems to attenuate towards the Late and Latest Famennian but this might be above all the result of the development, of cosmopolitan coastal lowland vegetations Ž.downstream swamps depending more on the moisture and equable local microclimates than on the probably adverse climates of distant hinterland areas. During that time, periods of cold climate without perennial snow cover and with rare vegetation may have alternated with less cold but wetter climates, thus giving rise to the development of mountain glaciers in high latitudes and explaining the jerking character of the global major marine regression. In high latitude regions, the development of an ice cap reaching sea level is only recorded by the end of the Latest Famennian, immediately below the DCB but, even if glacial evidences are not known at near the FFB, a shortŽ. 0.1 Ma? glaciation seems the best reasonable explanation of the major eustatic fall following the Kellwasser Event. The sudden growth and decay of a hypothetical

) Corresponding author. Tel.: q32-4-366-5498; fax: q32-4-366-5338. E-mail address: [email protected]Ž. M. Streel .

Earliest Famennian ice sheet can be explained by the reduction and, later, increase in greenhouse capacity of the atmosphere.

These changes in the atmospheric CO2 might have provoked changes in the mode of ocean-atmosphere operation. It may also be partly controlled by a volcanic paroxysm andror bolide impacts. The Hony microtektites represent the best known evidence of the impact of extraterrestrial bodies on Earth corresponding to the UKW, and they are immediately followed by a regression, suggested by the quantitative analysis of acritarch assemblages. In the paleo-tropical Late Famennian, a peat-forming vascular plant community occurs for the first time and makes possible quantitative palynology of autochthonous sediments allowing the recognition of different swamp and near-swamp characteristic miospores. The early Latest Famennian starts with a widespread transgression which could correspond to the melting phases of the hypothetical Late Famennian mountain glaciers. During the end-Famennian, the coastal lowland vegetation has a worldwide distribution from sub-polar to equatorial regions. The climate has become less cold in high latitudes but wetter than before probably because the midlatitude cyclonic activity allows sufficient polar transportation of moisture to form large snow cover. Extensive coastal glaciers developed in different Bolivian and Brazilian basins, well dated by miospores. Rapid climatic changes characterize the onset of glaciation. The cyclic nature of climate allowed even intertropical marine faunas to reach occasionally the subpolar regions. For the plant kingdom, the crisis which follows the Hangenberg Event was more severe than the Late Frasnian Crisis. q 2000 Elsevier Science B.V. All rights reserved.

Keywords: Late Frasnian±Famennian climates; palynomorph analyses; Late Devonian glaciations

1. Introduction Isaacson et al.Ž. 1999 , of Late Famennian and Tour- naisian ages; after Loboziak et al.Ž. 1993 , of late The Famennian Stage is bracketed by two main Latest Famennian age; after CaputoŽ. 1985 , of mid- crises and two events in the biosphere: the Late Famennian age. According to Veevers and Powell Frasnian Crisis and the Kellwasser Event near the Ž.1987 and Smith Ž 1997, p. 167 . , a glaciation might FrasnianrFamennian BoundaryŽ. FFB , the end- have occurred during the entire Famennian. Too Famennian Crisis and the Hangenberg Event near the often also, glaciation is confused with global cooling DevonianrCarboniferous BoundaryŽ. DCB . We con- ignoring the fact that, if glaciation requires cold sider a crisis in the biosphere to represent a rather climate, it also does require heavy snowfall. long time interval, during which the biodiversity Few contributions to the understanding of Devo- deteriorates, often resulting in a stepwise loss of nian climates rely on terrestrial vegetation data de- taxa. On the contrary, an event is considered to be a spite the fact that its impact on the biosphere was geological short-term perturbation compared to pre- very important during that periodŽ Tappan, 1982, ceding and succeeding time intervalsŽ Walliser, 1990; 1986; Algeo and Scheckler, 1998. . Indeed a massive Schindler, 1993. . Of course, the abruptness of a increase of land plant biomass from Middle Devo- short-term perturbation is difficult to establish in the nian to Early Carboniferous timesŽ. Berner, 1990 and geological pastŽ. Van Loon, 1999 and one can con- the increased rate of organic matter burial during sider that crises and events might be only two facets major transgression pulsesŽ. Caputo, 1994 is be- of the same phenomenon. lieved to explain the long-term shortage of atmo-

The proposed causes of crises and events are very spheric CO2 at this time. The reason of this scarcity diverse, and climate change is only one of them of information has to be found in the scattered and which we intend to focus onŽ other proposed causes poorly dated occurrences of plant megafossils in the are bolide impacts, tectonism, oceanic overturn, eu- geological record at this time. It is also the result of static fluctuations, etc. . The Famennian climate itself the continued misconception that even miospores, is often reduced to the question: glaciation or no produced by these land plants, are poorly correlated glaciation? According to DickinsŽ. 1993, p. 90 , with marine faunasŽ see for instance McGhee, 1996, BeckerŽ. 1993 and House Ž. 1996 , there was no p. 187. . glaciation during the Famennian and the Earliest We believe that land plant miospores, which are Carboniferous. After BoucotŽ. 1988, p. 223 , the much more abundant and widespread than land plant glaciation might be of Early Carboniferous age; after megafossils, can supply reliable quantitative data M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 123 with which to understand climate changes. They are witnessing to the development of the tree habit in generally found not only in continental deposits but lycophytes and progymnosperms, with changes in also in marine environments where they are deliv- the reproductive biology of the latter. Archaeopteris ered by wind and fluvial systems, and there, mixed is the most representative progymnosperm genus, with other palynomorphs and also with marine fos- whereas its iso- or micro-spore, Geminospora lemu- sils allowing accurate dating. Other palynomorphs rata, is among the most widespread miospores dur- include acritarchs, which represent the fossil part of ing this same timespan. They can be used to show the phytoplankton forming a base of the trophic the global distribution of this fossil group. Since the pyramid of oceanic ecosystems, and chitinozoans, end of Middle Devonian, Archaeopteris and G. which may represent eggs in the life cycle of a lemurata had an apparently wide range of tolerances, cryptic fossil group: the Achitinozoan animalB ŽParis ranging from paleo-equatorial to paleo-boreal lati- and Nolvak, 1999. . tudes and from seasonally dry to wet habitats Ž.Scheckler et al., 1999 . This homogeneity is explained by the position of Gondwana relative to 2. Middle Devonian to Frasnian phytogeography North America and Europe which set up potential and climates, a prerequisite for the interpretation monsoonal circulation pattern making the climate in of Late Frasnian±Famennian climates the deep tropics more savannah-like than everwet tropicalŽ. Bambach et al., 1999 . The entire Devonian was a time of profound The display of these data needs a suitable paleo- change both for terrestrial biotas and the physical geographic frame. We have to choose among many environment. However, the Middle Devonian and published maps based either on paleomagnetic or on Frasnian were particularly important epoch and age nonpaleomagnetic data.

Fig. 1. Paleophytogeographic reconstruction, after Streel et al.Ž. 1990, fig. 3b based on the Middle Devonian map of Heckel and Witzke Ž.1979 . Hatched area: Frasnian Archaeoperisaccus; black diamonds: G. lemurata. Miospore distribution after McGregorŽ. 1979 and Streel Ž.1986 . G. lemurata is also present, but not shown here, where Archaeoperisaccus is present. This is the map adopted throughout this paper. Geminospora has a worldwide distribution, Archaeoperisaccus distribution being centered on the equatorial belt. 124 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Miospores can help in selecting such a map by sitive rocksŽ. Witzke, 1990 and assumes a paleomag- using, for instance, the geographic distribution of netic pole which is slightly different from the rota- Archaeoperisaccus, a very distinct monolete mi- tional pole, a hypothesis, however, considered im- crospore, which was produced, during the Frasnian, probable by SmithŽ. 1997, p. 177 . Of course, the by a heterosporous plant that produced also the reliability of some paleomagnetic data may need to distinctive megaspore Nikitinsporites ŽMcGregor, be reevaluated. This reconstruction is partially 1969. . By comparison with the near-global distribu- matched by Boucot'sŽ. 1988 Late Devonian nonpale- tion of Geminospora, Archaeoperisaccus has a re- omagnetic reconstruction and is used by Vavrdova stricted distribution, a major control on its geo- and IsaacsonŽ. 1999 to display late Famennian graphic distribution being likely to have been the acritarch bioprovinces. limited transportation potential of the megaspore These maps differ from Scotese and McKerrow's within the limits of the corresponding ecological Ž.1990 paleomagnetic map Ž Fig. 2 . where the paleo- domainŽ. Marshall, 1996, p. 1136 . equator crosses through Hudson Bay and the west- Heckel and Witzke'sŽ. 1979 Middle Devonian ernreastern border of Europe. The inadequacy of the nonpaleomagnetic reconstructionŽ. Fig. 1 seems to latter reconstruction is obvious. A comparison with be the most appropriate map for displaying the Ar- late Quaternary vegetation maps shows that the mod- chaeoperisaccus distribution. It restricts the location ern-day vegetation is distributed more or less equally of Archaeoperisaccus microspores to a paleo-inter- on both sides of the equator, even during the LGM tropical belt situated between 358N and 208S, the Ž.Ž.Late Glacial Maximum time Adams et al., 1990 . paleo-equator crossing western North America near This is mainly the result of a similar thermoperi- the Alaskan border and eastern Europe near the odism in the equatorial beltŽ Went, 1953; Streel, UralsŽ. Streel et al., 1990, fig. 3 . This reconstruction 1962. . Indeed, the key characteristic of this belt is based on the distribution of paleoclimatically sen- today is not warmth or humidity, which can vary

Fig. 2. Paleophytogeographic reconstruction based on the Late Devonian map of Scotese and McKerrowŽ. 1990, fig. 16 . Hatched area: Frasnian Archaeoperisaccus distribution as in Fig. 1. This map is not used because the Archaeoperisaccus distribution is shown to be limited by the equator line on its southern side, which is unlikely. M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 125 considerably from tropical savannahs to rainforests; Ž.1979 reconstruction, the equatorial belt was thus rather, it is the relative constancy of conditions, i.e., centered on northwestern Canada and western USA, the comparatively low level of environmental fluctu- as well as on eastern Europe, a single province called ationsŽ. Meyerhoff et al., 1996, p. 3 . If the Frasnian here northern Euramerica. Southern Euramerica was Archaeoperisaccus distribution was dependent on the centered on eastern Canada and USA and on western same climatic factors, its locationŽ. Fig. 2 only on Europe, representing a tropical beltŽ a subtropical the northern side of the equatorial lineŽ implied by belt on northern Africa. . Scotese and McKerrow'sŽ.. 1990 map is unlikely. Of Avkhimovitch et al.Ž. 1993 show the correlation course, during no time interval of the past there is Ž.Fig. 3 , based on conodonts, between Givetian and evidence for a perfect latitudinal biotic distribution most of the Frasnian miospore assemblages from, owing to the complex interactions of varied longitu- respectively, northern and southern Euramerica. dinal barriersŽ. Meyerhoff et al., 1996, p. 5 . How- These assemblages are poorly correlatable on the ever, the bipolar distribution of various biotas basis of miospores themselvesŽ Loboziak and Streel, normally appears as at least three distinct zones, 1981; Streel and Loboziak, 1996. because these including two polar-centered biotic units, one boreal miospore assemblages are rather different. On the and one austral, and at least one unit lying between contrary, the presence of 12 Givetian-Frasnian the polar units. Of course, the absence of a boreal miospore-events in the same order of occurrence in belt in Heckel and Witzke'sŽ. 1979 reconstruction western EuropeŽ. southern Euramerica , Northern results from the absence of northerly continents. The Africa and BrazilŽ.Ž western Gondwana indicates Fig. inadequacy of Scotese and McKerrow'sŽ. 1990 map 4. similar changes in vegetation composition and is also obvious from the distribution of Famennian therefore probably similar climatic conditions rang- and lowermost Tournaisian marine deposits yielding ing from tropical to subpolar areasŽ Streel et al., RugosaŽ. Poty, 1999, fig. 1 , which is not centered on 1990, fig. 1.Ž . It contradicts as did also Paris and the equator of this map but rather on a parallel some Robardet, 1990, p. 206.Ž. Van der Voo's 1988 Late 158 to the north. According to Heckel and Witzke's Devonian paleomagnetic reconstruction which esti-

Fig. 3. Correlation chart between southern and northern Euramerican miospore zonations after Avkhimovitch et al.Ž. 1993, fig. 4 modified . ) sconodont data in northern Euramerica; for conodont data in southern Euramerica, see correlation conodont-miospore in Streel et al. Ž.1987 . The detailed correlation is possible by conodonts, not really by miospore assemblages, which are different in southern and northern Euramerica. 126 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 4. Correlation, within western Gondwana, between two boreholes, respectively, from subpolarŽ. Brazil and subtropical Ž. Libya regions, after Streel et al.Ž 1990, fig. 1. Used with the permission of the Geological Society Publishing House. . Seventeen species are designated by capital letter. Miospore zonation from tropical southern EuramericaŽ. western Europe after Streel et al. Ž. 1987 . Single arrows indicate the miospore-events, which have the same order of occurrence in western Europe, Libya and Brazil. Double arrows indicate condensed portions of the sections. mates an ocean 3000 km wide between Euramerica equatorial. vegetations seem to have extended their and Gondwana. range into higher latitudes from Givetian to Frasnian The homogeneity of miospore assemblages from Ž.Fig. 5 . Morphologically elaborate miospores char- paleo-tropical to paleo-subpolar regions was even acteristic of western Gondwana almost disappear at more obvious during the Frasnian than during the the end of the Givetian, paralleling the faunal trend GivetianŽ.Ž Streel et al., 1990, fig. 2 . Tropical non- towards cosmopolitanism which had started in the M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 127

Fig. 5. Quantitative distribution of various miospore classes in different regions of western Gondwana and southern Euramerica, after Streel et al.Ž 1990, fig. 2. Used with the permission of the Geological Society Publishing House. . Note that percentages are of specimens, not of species.Ž. a Morphologically simple Ž smooth or finely sculptured, one-layered . miospores, Ž b±e . morphologically elaborate miospores, Ž. b occurring in all regions,Ž. c never found in Gondwana, Ž. d only found in Gondwana, Ž. e only found in Brazil Ž ParanaÂ Basin . . In western Gondwana, the amount of Gondwanan taxaŽ. d is decreasing Ž Brazil . or disappearing Ž North Africa . from the Late Givetian upwards.

GivetianŽ. Boucot, 1988; Sablock, 1993 and corre- rapidly from a subtropical to polar positionŽ Scotese sponded to the development of a rather hot climate et al., 1999, p. 100. . and an extended carbonate platform belt which reached paleolatitudes up to 458SŽ Heckel and 3. Evaluation of an accurate Late Frasnian± Witzke, 1979.Ž during the Frasnian the Awarm modeB Famennian timescale of Frakes et al., 1992. . Miospores are known also in regions other than Palynomorphs cannot help much in defining a Euramerica and western Gondwana, e.g., China and timescale because their biozones are rarely based on Australia, but these have their own history that is evolutionary lineages. Ziegler and SandbergŽ 1990, beyond the scope of the present contribution. For 1994.Ž. ; Sandberg and Ziegler 1996 and Ziegler and instance, during the Late Devonian, the Indo± WeddigeŽ. 1999 have proposed that conodonts can Australian±Antarctic region of Gondwana moved be used for that purpose, each conodont zone averag- 128 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 6. Chronostratigraphy, geochronology and standard conodont zones of Givetian to Early Carboniferous, after Sandberg et al.Ž 1997, fig. 2. Used with the permission of the first author.Ž. . Sub-ages of the Famennian after Streel et al. 1999 . Only the Kellwasser and the Hangenberg events are concerned by this paper. The other events, which do not correspond to major biotic crises, are only shown to help correlation. M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 129 ing about a half million years in duration. We are aware of course that evolutionary events cannot be demonstrated to occur at the same rate in any stratigraphic intervalŽ see also Fordham, 1992 for discussion. . But in order to subdivide the Late Devonian Epochs, the conodont-based scale is the most often used and, moreover, its subdivision in time units makes the calibration of events easierŽ. Fig. 6 . Originally, Late Devonian conodont zonal boundaries were dated backwards from a starting point of 0 Ma at the DCB. Ties to the radiometric time scale were avoided because of the often controversial dat- ingsŽ. McGhee, 1996, p. 7 proposed for the DCB Ž.Sandberg et al., 1997 . The finding, by Claoue-LongÂ et al.Ž. 1992, 1993 , of a new, biostratigraphically controlled zircon fission-track date of 353.2 Ma from a bentonite layer deposited just above the base of the Earliest Carboniferous sulcata Zone led Sandberg and ZieglerŽ. 1996 to redate the DCB to 354 Ma. Recently, Tucker et al.Ž. 1998 claimed to have obtained new U±Pb zircon dates from a series of volcanic ashes closely tiedŽ supposed better than before.Ž. to biostratigraphic zones. 1 The Late Fa- Fig. 7. Diversity of miospore species in the Devonian. Data from mennian new data, which are assumed by Tucker et Richardson and McGregorŽ. 1986 . Modified from Boulter et al. Ž. Ž Ž. 1988 , after McGhee 1996, fig. 4.24 redrawn. Used with the al. 1998 to date the Fa2d part of the Belgian scale, permission of the author. . The diversity of miospore species i.e., the Late expansa conodont Zone, are not con- shows a maximum during the Givetian and the Frasnian and a firmed by facts. They are based on a palynological rather dramatic drop between the Frasnian and the Famennian. analysis of the Carrow Formation of the Piskahegan Group in southern New Brunswick made by McGre- gor and McCutcheonŽ. 1988 . However, these authors i.e., within the Latest marginifera Zone, thus 4 to 5 could not really distinguish between their millions years older than the DCB.Ž. 2 The new pusillites±lepidophyta ZoneŽ. Fa2d and flexuosa± Early Frasnian data are claimed by Tucker et al. cornuta ZoneŽ. Fa2c . Indeed, one single specimen of Ž.1998 to characterize the punctata to Late hassi one species only Ž Retispora lepidophyta?, pl. 2, figs. conodont Zones. It is based on an unpublished deter- 15, 16. has been found which might indicate the mination by them of P. punctata from the Chat- pusillites±lepidophyta Zone. But, with our present tanooga Shale at Little War Gap, east Tennessee experience of the R. lepidophyta MorphonŽ Stee- Ž.USA , formerly attributed by Dennison and Boucot mans et al., 1996. , we believe that this specimen Ž.1974 to the Eifelian on the basis of brachiopod most probably belongs to R. cassicula Žnow R. data. However, the presence of the brachiopod macroreticulata. which first occurs in the Latest Leiorhynchus limitare in the Tioga tuffaceous beds marginifera conodont Zone in BelgiumŽ Streel and at the base of the Chattanooga Shale still supports an Loboziak, 1996, text-fig. 3. . In the absence of R. Eifelian ageŽ a late Eifelian age according to P. lepidophyta, the single specimen of V. pusillitesŽ V. Sartenaer, personal communication, December 1999. . pusillites sensu lato, pl. 3, fig. 7. might belong to the Consequently, we believe that the Late Famennian pusillites±fructicosa Zone of Richardson and Ahmed Ž.363.6"1.6 Ma and Early Frasnian Ž 381.1"1.3 Ž.1988 , the base of which is in the uppermost part of Ma.Ž. dates given by Tucker et al. 1998 are poorly the Ellicott Formation or in the lowermost part of the constrained biostratigraphically and, thus, for the Cattaraugus Formation in New York StateŽ. USA , time being, we prefer to adopt Sandberg and Ziegler's 130 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Ž.1996 chronology, that is 354 Ma for the DCB, 364 gorŽ. 1986 , the diversity of characteristic miospore Ma for the FFB and 369 Ma for the base of the species computed to the Stage levelŽ McGhee, 1996, Frasnian Stage. This is in line with Gradstein and fig. 4.24. clearly shows a maximum during the Give- OggsŽ. 1996 age and duration of the Famennian tian and the Frasnian and a rather dramatic drop Stage. from the Frasnian to the FamennianŽ. Fig. 7 . How- Since formal subdivisions of the Famennian age ever, according to Boulter et al.Ž. 1988 and Ray- have not yet been defined by the IUGS Subcommis- mond and MetzŽ. 1995, fig. 3 , also based on sion on Devonian Stratigraphy, we will use here the Richardson and McGregor'sŽ. 1986 data, but consid- following four sub-agesŽ. Streel et al., 1999 : Early ering genera rather than species at a substage level, Famennian, defined at the base of the Early triangu- miospore diversity shows a rather clear Late Fras- laris Zone and composed of seven conodont zones; nian-Middle Famennian minimumŽ. Fig. 8 . Middle Famennian, defined at the base of the Early More recent northern Euramerican data from rhomboidea Zone and composed of four conodont northwestern CanadaŽ. Braman and Hills, 1992 and zones; Late Famennian, defined at the base of the eastern EuropeŽ. Avchimovitch et al., 1993 clearly Latest marginifera Zone and composed of seven confirm a diversity crisis during the Late Frasnian to conodont zones, and Latest FamennianŽ. or Strunian , Middle Famennian timespan. The northwestern defined at the base of the Late expansa Zone and Canadian dataŽ. Fig. 9 are the most interesting be- composed of four conodont zonesŽ. Fig. 6 . cause the complete miospore assemblage is given Žincluding morphologically simple, smooth or finely sculptured, one-layered species which are seldom 4. The Late Frasnian Crisis used to characterize assemblages. . Eighty-five taxa have last occurrencesŽ. LO taxa and only 14 first The Late Frasnian Crisis is often cited as one of occurrencesŽ. FO taxa in the Late Frasnian to Middle the major crises in the history of life on Earth. Famennian intervalŽ 46 LO against 5 FO in the Late Probably three-quarters of all animal species, more Frasnian, less than 2 Ma in duration, and 39 LO than half of all the generaŽ. Sepkoski, 1986 , more against 9 FO in the Early and Middle Famennian, than a fifth of all the familiesŽ. Sepkoski, 1982 did altogether 5 Ma in duration. . The eastern European not survive this crisis. The temporal duration of the dataŽ. Fig. 10 only concern the biostratigraphically Late Frasnian Crisis has been, and still is, the subject characteristic miospores and, therefore probably, the of considerable hot debate. However, a careful anal- diversity loss across the FFB is much less obvious ysis of available dataŽ. McGhee, 1996 demonstrates Ž42 taxa have last occurrences and 39 first occur- that the Late Frasnian diversity crisis is clearly not a rences in the Late Frasnian to Middle Famennian single instantaneous event as it occurs over 3.0 Ma at timespan: 20 LO against 10 FO in the less than 2 least, the main pulse of the extinction spanning about Ma-long Late Frasnian and 22 LO against 29 FO in 2.0 Ma, from the base of the Early rhenana Zone to the 5 Ma-long Early and Middle Famennian. . The the base of the Middle triangularis Zone. Often diversity minimum seems to be on the Frasnian side mentioned is the mass extinction of rugose corals rather than on the Famennian side of the transitional Ž.ŽSorauf and Pedder, 1986 and brachiopods Balin- timespan. ski, 1996; Copper, 1998; Racki, 1998a,b. . However, McLarenŽ. 1988, p. 2 , when invoking an Ainstan- the most devastating diversity loss occurs in the taneous eventB at the FFB, mentioned a major break linguiformis Zone, which might be of 0.3 Ma in in miospore development at that time. He cited durationŽ. Sandberg et al., 1988 and is herein re- Richardson and McGregorŽ. 1986 in support of his ferred toŽ. see below as the Kellwasser Event. view, clearly referring to the oÕalis±bulliferusr torquata±gracilis Assemblage Zone boundary illus- 4.1. Miospores trated by these authorsŽ Richardson and McGregor, 1986, fig. 3. in the Latest Frasnian strata of New Considering undifferentiated northern and south- York StateŽ. USA , and where at least 10 species ern Euramerican data from Richardson and McGre- seem to have first occurrences at the same time M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 131

Fig. 8. Diversity of Middle Silurian through Late Devonian land plants using various diversity measurements: the dotted line represents the standing diversity of miospore genera at interval boundaries, taken from data by Richardson and McGregorŽ. 1986 ; the solid lines represent the mean generic richness of plant megafossil genera in each interval after KnollŽ. 1986 or data compiled by Raymond and Metz Ž. 1995 . After Raymond and MetzŽ. 1995, fig. 3 redrawn . The use of a sub-stage scale allows showing that the drop in miospore and plant megafossil taxa starts within the Frasnian.

immediately below the FFBŽ. Fig. 11 . But more served miospores have been collected from the Bri- recently, it became evident through the conodont quetterie de Beaulieu section. This section displays a study by OverŽ. 1997 that the torquata±gracilis rather detailed miospore zonal subdivisionŽ Loboziak Assemblage Zone first occurs in the lower part of the et al., 1983. within Zone AIVB and shows the base of Hanover Shale below the entry of the conodont the succeeding Zone AVB Ž.Fig. 13 . Zone AIVB has Palmatolepis linguiformis Žlikely within the range of some similarity, in miospore composition, with the Palmatolepis juntianensis comparable with the Fras- Latest Frasnian C. deliquescens±V. eÕlanensis Zone nian Montagne Noire conodont zonation of Klapper Žthe DE Zone comprising the AS and GS Subzones, and Foster, 1993. . Besides, there was a large sam- after Avkhimovitch et al., 1993. , described in eastern pling gap in the New York State section below this Europe, which characterizes the equatorial belt at level because the oÕalis±bulliferus Assemblage Zone that same timeŽ. Fig. 3 . The base of this zone, last occurs in the Rhinestreet Shale, three lithostrati- starting with the entry of Cymbosporites acan- graphic units below the Hanover Shale, i.e., in the thaceus, corresponds to the Late rhenana conodont hassi or jamieae conodont ZonesŽ. Fig. 12 . The Zone in eastern EuropeŽ Obukhovskaya et al., in dramatic end Frasnian change in New York State press. . The uppermost part of Zone AIVB is dated section is a sampling, and maybe also a fossil preser- with acritarchsŽ. Loboziak et al., 1983 known from vation, artifact, the younger assemblage starting with the transitional Late rhenana±linguiformis Zones poorly preserved materialŽ Richardson and Ahmed, ŽMartin, 1993, fig. 9; Bultynck and Martin, 1995, 1988, p. 545. . Fig. 2. . Zone AVB is characterized by the first entry In the Hydrequent FormationŽ Boulonnais, north- of three species Ž Knoxisporites dedaleus, K. cf. hed- ern France. , the Late Frasnian does not show any eratus and Diducites Õersabilis. of which only one major break in the succession of corresponding as- Ž.K. dedaleus starts at the base of the torquata- semblages. Samples with abundant and well-pre- gracilis Assemblage Zone of Richardson and Mc- 132 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

GregorŽ. 1986 . Eighteen species gradually disappear from Zone AIVB to the beginning of Zone AVB. Two and 25 gradually appear in the interval spanning species Ž Diducites poljessicus and Grandispora gracilis. marking the base of the torquata-gracilis As- semblage Zone of Richardson and McGregorŽ. 1986 occur within Zone AIVB. Therefore, the sharp turnoverŽ. Fig. 11 illustrated by Richardson and Mc- GregorŽ. 1986, fig. 3 cannot be observed in the Boulonnais area. The Latest Frasnian is characterized by a miospore assemblageŽ the C. deliquescens±V. eÕlanensis Zone. from eastern Europe which, excep- tionally during the Frasnian, is rather similar both in equatorial and tropical regions suggesting that the equatorial climatic belts had reached a maximum width in the Latest Frasnian.

4.2. Land plants

According to Boulter et al.Ž. 1988 and Raymond and MetzŽ. 1995, figs. 2 and 3 , the diversity of land plant genera at substage boundaries also shows a clear Late Frasnian±Middle Famennian minimum Ž.Fig. 8 . The number of genera and number of investigated localities are rather low for this interval but statistical tests suggest that poor sampling does not cause the observed diversity minimumŽ Raymond and Metz, 1995, table 6. . It is not possible, however, to discriminate between the Late Frasnian and the Early±Middle Famennian data so that no conclusion can be drawn for the time being.

4.3. Acritarchs

Although TappanŽ. 1971, fig. 1 clearly shows that acritarch diversity collapses at the DCB, and not at the FFB, McGheeŽ. 1996 used the diversity evaluation of acritarchsŽ including Prasinophycean green algae.Ž at a poor resolution level, i.e., the Epoch see

Fig. 9. Composite stratigraphic ranges of miospores across the FFB, conodont and miospore Zonation, from western Canada, after Braman and HillsŽ. 1992, text-fig. 5 modified . The loss in miospore diversity obviously starts in the Late Frasnian. Eighty- five taxa have last occurrencesŽ. LO taxa and only 14 first occurrencesŽ. FO taxa in the Late Frasnian to Middle Famennian intervalŽ 46 LO against 5 FO in the Late Frasnian which has less than 2 Ma in duration, and 39 LO against 9 FO in the Early and Middle Famennian which have altogether 5 Ma in duration. . M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 133

Fig. 10. Composite stratigraphic ranges of selected miospores across the FFB and miospore Zonation from eastern Europe, after Avkhimovitch et al.Ž. 1993, fig. 3 modified . These eastern European data only concern the biostratigraphically characteristic miospores and, therefore, the diversity loss across the FFB is less obvious than in Fig. 9. Forty-two taxa have last occurrences and 39 first occurrences in the Late Frasnian to Middle Famennian timespanŽ 20 LO against 10 FO in the less than 2 Ma-long Late Frasnian and 22 LO against 29 FO in the 5 Ma-long Early and Middle Famennian. .

Fig. 11. Distribution of characteristic miospores across the FFB from the Old Red Sandstone Continent and adjacent regions, after Richardson and McGregorŽ. 1986, fig. 3 modified . Ten taxa seem to have first occurrences, at the same time, immediately below the FFB. This is a sampling, and maybe also a fossil preservation, artifact. 134 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 12. Generalized latest Givetian, Frasnian and Early±Middle Famennian chrono-and litho-stratigraphy of western New York State and correlation between two independent conodont zonations after OverŽ. 1997, fig. 1 modified. Used with the permission of the author . Conodont zonations: narrow right column after KlapperŽ. 1988 , other data after Ziegler and Sandberg Ž. 1990 . Miospore zonation after Richardson and McGregorŽ. 1986 . The correlation conodontrmiospore illustrates the importance of the gap between the torquata±gracilis and the oÕalis±bulliferus assemblage-zones.

Tappan and Loeblich, 1972, p. 206 for genera diver- that the dramatic decline of acritarchs occurs near sity; Tappan and Loeblich, 1973, p. 215 for species the end of the FamennianŽ. Fig. 14 , not near the diversity.Ž . He claims, as many others Stanley, 1984, FFB. p. 207; Schindler, 1993, p. 117; Klapper et al., 1993, p. 435; Walliser, 1995, p. 234; Schulke,È 1998, p. 93. , 4.4. Chitinozoans that the phytoplankton was drastically reduced in the Late Frasnian Crisis. Despite these assertions, paly- Following their Silurian acme, the specific diver- nologistsŽ Bouckaert et al., 1972; Vanguestaine, sity of chitinozoans declined progressively from the 1986; Martin, 1993; Strother, 1996. have confirmed Lochkovian onwards and ended with the extinction M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 135

Fig. 13. Distribution of characteristic miospores, acritarchs and miospore zonation from the Hydrequent Formation in the Boulonnais area Ž.northern France , after Loboziak et al. Ž 1983, fig. 1 modified . . Conodont correlation after Obukhovskaya et al. Ž. in press . Acritarchs E. media and V. occultata are known from the transitional Late rhenana±linguiformis conodont Zones The FFB is unknown between the base of miospore zone V and the Ste Godeleine Fm. Eighteen species gradually disappear and 25 gradually appear in the interval spanning from Zone AIVB to the beginning of Zone AVB. Two species Ž.Diducites poljessicus and Grandispora gracilis that mark the base of the torquata±gracilis Assemblage Zone of Richardson and McGregorŽ. 1986 occur within Zone AIVB. of the group in the Latest Famennian. It is worth Ž.ŽSandberg et al., 1988 and ammonoids House, 1985, noting that the Achitinozoan animalsB survived the 1989. are most often considered. What about land FF mass extinction, despite the fact that diversity of plants and palynomorphs? the group had been declining for a long timeŽ Paris First we must realize that, with a time resolution and Nolvak, 1999. . at the Subzonal level, detailed event-stratigraphic investigations become more and more necessary. If rock sequences are subdivided on an extremely fine 5. The Kellwasser Event scale, high resolution correlations between different The most devastating diversity loss of Devonian sections and regions become more accurate and one faunas occurs in the linguiformis Zone, which may can realize, for instance, that what had been thought be of 0.3 Ma in duration, and is referred to here as of as a single event may also show a stepwise pattern the Kellwasser Event. Among many, mainly pelagic Ž.Schindler, 1993 . The succession of correlation lines fossil groups that were affected, the conodonts might represent time-slices of only some 10,000 136 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 14. Approximate stratigraphic distribution of acritarch-bearing sequences in the Upper Devonian and Lower Carboniferous after VanguestaineŽ. 1986, fig. 3 modified . Single line: spot samples, reduced or incompletely studied interval Ž. no proposed zonation ; double line: sequence studied in detailŽ. proposed zonation ; dashed line or question mark: poorly dated; full line: well dated. The dramatic decline of acritarchs occurs near the DCB, not near the FFB. yearsŽ. Schindler, 1993, fig. 7 . In many sections, ferruginous crust, a few mm thick, or above it, rather observations concentrate on the Upper Kellwasser than at its base as formerly proposed. Sedimentologi- HorizonŽ. UKW and lateral equivalents as well as cal and geochemical methods also provide a correla- layers immediately below and above that level. It is tion tool, but they are more important clues to envi- represented in the pelagic realm as an intercalation ronmental interpretationŽ Herbosch et al., 1997b; of dark sediments within lighter limestones or shales. Weis et al., 1998. . The UKW is generally admitted A worldwide synchronous character of this lithologi- to represent a spreading of dysoxic facies coinciding cal unit is often claimedŽ. Walliser, 1995 . with a rapid transgression followed by a strong The FrasnianrFamennian Global Stratotype Sec- regression right at the stage boundaryŽ Sandberg et tion and PointŽ. GSSP has been fixed Ž Cowie et al., al., 1988. . 1989.Ž in the Coumiac Section Montagne Noire, Palynomorphs have been obtained from the UKW southern France. at a level between the Palmatolepis at Coumiac but are too poorly preserved for precise linguiformis and P. triangularis Zones of the stan- identificationŽ. Klapper et al., 1993, p. 439 . Chitino- dard conodont zonation. But here the limits of bios- zoans and Prasinophycean green algae Ž.Maranhites tratigraphy are reached. For instance, P. triangularis were found in the Montagne Noire at La Serre, 30 and P. praetriangularis Žthe latter occurring in the km from the Coumiac quarry. At La Serre, the FFB linguiformis Zone. are sometimes considered as syn- falls within interbedded anoxic dark shales and lime- onymous and even the occurrence of a few speci- stones. The almost complete absence of miospores mens of P. triangularis is accepted by Klapper et al. and acritarchs in these beds is probably related to the Ž.1993, p. 436 in the Frasnian linguiformis Zone. distal situation of the deposition siteŽ Paris et al., Also, the resolution obtained with the evolution of 1996. . The major result from this section is the conodont biofacies changes is believed, at the genus exceptional chitinozoan concentration in the basal- level by GirardŽ. 1995 and at the species level by most Famennian bedŽ Paris et al., 1996, fig. 2, in SchulkeÈ Ž. 1998 , to be finer than the standard bio- part reproduced here as Fig. 15. . zonation. So, the FFB at the stratotype of Coumiac In order to observe miospores and acritarchs dur- has, after GirardŽ. 1995, p. 692 , to be placed within a ing the Kellwasser Event, we need neritic facies that M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 137

nomorphs, if any, is only of quantitative character. Important exceptions are the first occurrences of the acritarchs V.? occultata and Ephelopalla media ŽFig. 16. which seem to represent good markers for the transitional Late rhenana-linguiformis Zones times- panŽ. Martin, 1993; Bultynck and Martin, 1995 and had been used higher up to date the upper part of the Briquetterie de Beaulieu section in the Boulonnais area. More detailed data on the systematics and quantitative rates of acritarch species across the FFB at Hony and Sinsin is beyond the scope of the present paper. Here we will focus on the concentra- tionŽ number of specimens, not of species, per gram of sediment. of acritarchs and miospores, as fossil groups, in restricted shaly intervals. Of course, it is not well known how much of the boundary limestone in the GSSP is here represented by shale. Since the palynological analysis published over 10 years agoŽ. Streel and Vanguestaine, 1989 , both sections have attracted further investigations which are important for their stratigraphic and sedimentological interpretation. One of the sectionsŽ. Hony has also become famous for the discovery of microtektites Ž.Ž.Claeys et al., 1992 near the FFB see later . Fig. 15. Chitinozoan distribution and abundance in the Frasnian± Famennian boundary beds in section C at La SerreŽ Montagne Noire, southern France.Ž , reprinted from Paris et al. 1996, fig. 2 modified. Used with permission of the first author.Ž. . 1 Grey 5.1. Hony section limestone;Ž. 2 light grey limestone; Ž. 3 black laminated micritic limestone;Ž. 4 weathered marly shale; Ž. 5 calcareous nodules. The The most important acritarch data related to the exceptional chitinozoan concentration in the basal-most Famen- Ž nian beds fits rather well a global cooling hypothesis at that level FFB were published by Vanguestaine et al. 1983, as cold water seems to have been more favorable for the prolifera- fig. 6, reproduced here as Fig. 17. . A major quantita- tion of these microfossils. tive change is shown near that boundary in the Hony section for nine selected species. The time resolution is, however, too poor to allow evaluation of the also yield conodonts to correlate with the GSSP. The Kellwasser Event. Indeed, studied samples around former reference section of the base of the Famen- that level are spaced far too apart for allowing nian at SenzeillesŽ. southwestern Belgium contains detailed analysis. At Hony, 150 cm of shale separate acritarchsŽ. Martin, 1985 but is poorly dated by the last Frasnian limestone with conodonts of the conodontsŽ. Bultynck and Martin, 1995 . The Hony linguiformis Zone from the first Famennian lime- and Sinsin sectionsŽ 40 km apart from each other, in stone with conodonts of the Early triangularis Zone. southeastern Belgium. have diagnostic conodont fau- Conodont biofacies indicate a regressive trendŽ abun- nasŽ. Sandberg et al., 1988 and abundant acritarchs dant Icriodus. in both limestones. The shale subdivi- ŽVanguestaine et al., 1983; Streel and Vanguestaine, sion is twofold: a grey unit containing coquina lay- 1989. . Miospores, although present and sometimes ers, 115 cm thick, at the base, and a dark-grey unit, rather abundant, are poorly preserved and surpris- 35 cm thick, at the topŽ. Sandberg et al., 1988 . ingly not very diverse. One can immediately remark Olive-green shale is present below in the Frasnian that there first occurs only a few acritarch species in and starts again on the top of the Famennian lime- these sections. The UKW influence on these paly- stone. 138 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 16. Selected Frasnian±Famennian acritarchs from BelgiumŽ. not to scale , reprinted from Martin Ž 1993, fig. 9. Used with permission of Cambridge University Press.Ž. . a Daillydium pentaster;b Ž.Visbysphaera? fecunda;c Ž.V.? occultata;d Ž.E. media;e Ž.Villosacapsula ceratioides;fŽ.V. globosa. Ž. c and Ž d . seem to represent good markers for the transitional Late rhenana±linguiformis Zones timespan.

AcritarchsŽ. spiny acritarchs show a continuous part of the shelf basin where a dominance of decrease from 10,000 sp.rgr.sed. at the base of the acritarchs was progressively replaced landward by a lower unit to nothing at its top and in the upper unit dominance of miosporesŽ. hypothesis A of Fig. 19 . Ž.Fig. 18 . They increase again up to 6000 sp.rgr.sed. Several authorsŽ Claeys, 1993; Claeys et al., 1994, in the olive-green shale above the top of the Famen- 1996; Herbosch et al., 1996, 1997a. have subse- nian limestone. Miospores oscillate between 600 and quently proposed that the upper unit probably repre- 2800 sp.rgr.sed. along the lower unit. They almost sents a deepening of the depositional environment. disappear in most of the upper unit except for the They also demonstrated, through geochemical analy- last 10 cm where they increase again and become ses, that chalcophilous elements show an increase more abundant in the olive-green shale on the top of within this upper unit, suggesting an abrupt input of the first Famennian limestone. The successive de- poorly oxygenated watersŽ Oxygen Minimum Zone creasing and increasing upward trends of acritarchs or OMZ. into a relatively shallow marine environ- were interpreted by Streel and VanguestaineŽ. 1989 ment. They assume that this level must be equivalent as a progressive regression culminating in the depo- to the UKW. Recently, a new sedimentological anal- sition of the dark grey shaleŽ. the upper unit during ysis based on microfacies studyŽ X. Devleeschouwer, which a sudden acceleration of the sedimentation personal communication, June 1999. confirms the rate was believed to have diluted the palynomorphs, deepening interpretationŽ. Fig. 18 . followed by a new transgression. They concluded This alternative interpretation has some conse- therefore that the palynomorphs originated from that quences for the palynomorph quantitative interpreta- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 139

Fig. 17. Relative percentages of nine selected species of acritarchs around the FFB at HonyŽ. Belgium , after Vanguestaine et al. Ž 1983, fig. 6 modified.Ž. . a Baltisphaeridium aff. longispinosum;b Ž.Hercyniana sprucegroÕensis;c Ž.Visbisphaera? fecunda;d Ž.Baltisphaeridium cf. crebum;eŽ.Dilatisphaera? sp. A; Ž. f Diexallophasis remota;g Ž.Villosacapsula globosa; Ž. h Herkomorphitae sp. A ŽsV.? occultata in Fig. 16.Ž. ; i Baltisphaeridium medium ŽsEphelopalla media in Fig. 16 .Ž.Ž. . f and g are known below in Belgium; Ž.Ž. h and i are the markers referred to in Fig. 16. Studied samples around the FFB are spaced far too apart for detailed analysisŽ. compare with Fig. 18 . tion. In a second hypothesisŽ hypothesis B of Fig. bed with conodonts of the linguiformis Zone from 19. , one can accept that miospores were transported the first Famennian limestone with conodonts of the for long distances offshore by bottom return flows as Early triangularis Zone. Conodont biofacies indicate a consequence of the storm waves, resulting in their a regressive trendŽ. abundant Icriodus in both lime- poor preservationŽ many corroded, unidentifiable stonesŽ. Sandberg et al., 1988, fig. 10 . The shale is specimens. . It would explain also the presence, subdivided twofold: the lower 12 cm are dark shales known only in these shales, of reticulate specimens containing limy lenses, some of them bearing con- formerly assigned to Corbulispora sp.Ž Loboziak and odonts of the linguiformis Zone; the upper 15 cm are Streel, 1981; Streel et al., 1987. , and now interpreted dark-grey shales. Olive-green shale is present below as the mesospore wall layers of freshwater algal in the Frasnian and starts again on the top of the Zygnematacea split along their equatorial regions Famennian limestone. In the lower 12-cm, acritarchs Ž.Grenfell, 1995 . According to this hypothesis, the and miospores are poorly represented except in one non-marine palynomorphs would have been re- sample. In the upper 15 cm, acritarch abundance worked from continental nearshore sediments and Ž.spiny acritarchs shows a continuous upward de- deposited in the distal part of the shelf basin where crease from 10,000 sp.rgr.sed. at the base of the the abundance of acritarchs is progressively reduced dark-grey shales to 3000 sp.rgr.sed., 10 cm higher. seawardŽ. hypothesis B of Fig. 19 . It increases again from 8000 sp.rgr.sed. to very high The Hony section would record, in a small cyclic values of 50,000 sp.rgr.sed. in the upper 5 cm of succession, a regression in the last Frasnian lime- these shales. Miospore abundance oscillates between stoneŽ. Sandberg et al., 1988, fig. 9 , a transgression 1800 and 3800 sp. gr.sed. in the lower 10 cm of the in most of the shaly interval, and again a regression dark-grey shales and increases again up to 8000 which accounts for the uppermost part of these shales, sp.rgr.sed. in the upper 5 cm of these shalesŽ Fig. the first Famennian limestone and the lower part of 20. . the succeeding olive-green shale. As explained for Hony, Streel and Vanguestaine Ž.1989 interpreted the successive decreasing and in- 5.2. Sinsin section creasing upward trends of the acritarchs as a progressive regression followed by a transgression. They At Sinsin section, about 27 cm only of dark and also remarked that the miosporeracritarch ratio dark-grey shale separates the last Frasnian limestone evolved in a similar fashion in both sections. They 140 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 18. Palynomorph stratigraphic distribution near the FFB at Hony, after Streel and VanguestaineŽ. 1989, fig. 2 modified . Lithology and conodont Zones and Biofacies after Sandberg et al.Ž. 1988, fig. 9 redrawn . Oxygen Minimum Zone Ž.Ž. OMZ after Claeys et al. 1996, fig. 7 . Sedimentological analysis based on microfacies studyŽ. X. Devleeschouwer, personal communication, June 1999 indicates the existence of two relatively different shallow marine domains:Ž. 1 in the lower part of the lower unit, a zone where the sea floor was affected by storm waves but not by fair-weather waves and where sediments show evidence of frequent storm reworking;Ž. 2 in the remaining part of the lower unit and the major part of the upper unit, a zone where sediments were deposited below the storm wave base. Allochthonous faunal and floral elements were transported from nearshore environments to deeper environments. In the uppermost dark-grey shale, microfacies indicate a brief return to shallower conditions where sparse and distal tempestite deposition may occur. AcritarchsŽ. spiny acritarchs show a continuous decrease from 10,000 sp.rgr.sed. at the base of the lower unit to nothing at its top and in the upper unitŽ. this figure . They increase again up to 6,000 sp.rgr.sed. in the olive-green shale above the top of the Famennian limestone. Miospores oscillate between 600 and 2800 sp.rgr.sed. along the lower unit. They almost disappear in most of the upper unit except for the last 10 cm where they increase again and become more abundant in the olive-green shale on the top of the first Famennian limestone. hesitated to conclude that similarity implies contem- where the abundance of acritarchs is progressively poraneity, although noting that the dark-grey shales reduced seawardŽ. hypothesis B of Fig. 19 . We present at Hony might be missing at Sinsin. Subse- propose also that the similarity in the concentration quently, Casier and DevleeschouwerŽ. 1995 discov- curves of miospores and acritarchs in both Hony and ered a very rich and well preserved ostracod fauna in Sinsin sections is indicative of their contemporane- the upper 5 cm of the dark-grey shales. This assem- ity, also with the significant difference that a major blage is indicative of a brackish-water environment part of the dark-grey shale at Hony is missing at with strong marine influence and clearly corresponds SinsinŽ. Fig. 20 . to a regression in that part of the shales which Streel In both sections, we observe successively a re- and VanguestaineŽ. 1989 had attributed to a transgression in the last Frasnian limestones or shales gression. containing limy lensesŽ. Sandberg et al., 1988 , a We propose therefore that, at Sinsin, paly- transgression in most of the shaly interval culminat- nomorphs originated from that part of the shelf basin ing at Hony in the development of oxygen-poor M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 141

Fig. 19. Hypothetical distribution of palynomorphs in sea basin. After JekhowskyŽ. 1963 , modified. According to hypothesis B, the non-marine palynomorphs would have been reworked from continental nearshore sediments and deposited in the distal part of the shelf basin where the abundance of acritarchs is progressively reduced seaward. bottom waters and again a regression in the upper- this stratigraphic interval can be assumed to corre- most part of these shales, with a possible sedimen- spond to the topmost 2.5 m of the section containing tary gap at SinsinŽ Casier and Devleeschouwer, in succession the acritarchs V.? occultata and E. 1995. . We must remember now that the Kellwasser media Ž.Fig. 13 . We do not know, however, the Event is generally admitted, in the Rhenish regions exact location of the FFB in this section. The sharp at least, to represent a spread of dysoxic facies contact between the marine Hydrequent Shales and coinciding with a rapid transgression and that the the overlying, palynomorph barren, Sainte Godeleine transgression reversed subsequently into a strong Sandstones might even represent it. Therefore, we regression right at the stage boundary. We suggest cannot confirm any changes, even of a quantitative therefore that the FFB at Hony and Sinsin should be nature, in the miospore distribution at the FFB in the placed near the base of the regression within the Boulonnais area. The successive reduction and in- upper part of the dark-grey shales. creasing of miospore abundance at Sinsin and Hony It is evident that the Kellwasser Event did not might well be, as noticed for the acritarchs, of affect significantly the phytoplankton more than it sedimentological nature, not necessarily a conse- did with the chitinozoans. The almost complete ab- quence of a sudden but ephemeral change of the sence of acritarchs at the FFB may be explained by vegetation on Earth. However, it should be realized the sedimentary conditions, not necessarily by a that, for the time being, no continuous miospore genuine extinction. But what about the miospores? succession is known for certain across the FFB. To answer this question we have to move again Ž.Žsee the Late Frasnian Crisis, above to the 30 m thick. Briquetterie de Beaulieu section, of the Hy- 6. The causes of the Late Frasnian Crisis and the drequent FormationŽ. Boulonnais, northern France , Kellwasser event where shales with abundant and well preserved miospores and less numerous acritarchs are present Following the suggestion by McLarenŽ. 1970 that ŽLoboziak et al., 1983; Streel and Loboziak, 1994, the Late Devonian mass extinction might have been fig. 1. . No conodonts were recorded in this section triggered by the impact of an asteroid, the search for which is known to cover more or less the Late evidence of such impactŽ. s in the geological record rhenana-linguiformis Zones in a more nearshore fa- rapidly emerged. Also, the finding of an iridium cies than the Hony and Sinsin sections. There is no anomaly at the Cretaceous-Tertiary boundary by Al- lithological equivalent of the UKW in this facies, but varez et al.Ž. 1980 suggested a new approach for the 142 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 20. Palynomorph stratigraphic distribution near the FFB at Sinsin, after Streel and VanguestaineŽ. 1989, fig. 3 modified . Lithology and conodont Zones and Biofacies, after Sandberg et al.Ž.Ž. 1988, fig. 10 redrawn and modified . Oxygen Minimum Zone OMZ and ostracod assemblages, after Casier and DevleeschouwerŽ. 1995 . I: very rich ostracod fauna but poorly diversified characteristic of semi-restricted conditions; V: Myodocopid Ž.Entomozoacea and Cypridinacea ostracods characteristic of dysoxic conditions. In the upper 15 cm of the transitional shale unit, acritarch abundanceŽ. spiny acritarchs shows a continuous upward decrease from 10,000 sp.rgr.sed. at the base of the dark-grey shales to 3000 sp.rgr.sed., 10 cm higher. It increases again from 8000 sp.rgr.sed. to very high values of 50,000 sp.rgr.sed. in the upper 5 cm of these shales. Miospore abundance oscillates between 1800 and 3800 sp.rgr.sed. in the lower 10 cm of the dark-grey shales and increases again up to 8000 sp.rgr.sed. in the upper 5 cm of these shales.

Aimpact theoryB. But there are no anomalous concen- evidence of an impact of extraterrestrial body on trations of iridium so far in the sampled sections of Earth corresponding to the UKW, although as Wal- BelgiumŽ. Claeys et al., 1994; McGhee, 1996 and liserŽ. 1995, p. 236 notes Amicrotektites are found in nothing unequivocal, right at the FFB, around the various quantities in Paleozoic conodont samples world. from many layers lacking any indication of an un- Microtektites have been reported from two locali- usual geological or biological changeB. ties of Belgium: at SenzeillesŽ. Claeys et al., 1992 , The effect of an extraterrestrial body crash on near the uppermost part of the Early triangularis global climate has often been discussed. ALarge ZoneŽ. Bultynck and Martin, 1995 and at Hony amounts of debris from the vaporized bolide and Ž.Claeys et al., 1994 , at the base of the dark-grey impact site would be injected into the atmosphere. shales, i.e., immediately below the here suggested Such a global dust cloud could result in the total FFB. The absence of microtektites at Sinsin can be blockage of sunlight from the Earth's surfaceB ŽMc- explained by the sedimentary gap occurring at that Ghee, 1996, p. 163. and initiate a global cooling on level. The record at Senzeilles is doubtful because Earth resulting in a short glaciation. AEqually, the the glasses closely resemble the chemical composi- impact of a large extra-terrestrial body into the ocean tion of reflective beads used for road markingŽ Marini might also promote higher temperatures through the and Casier, 1997. . It is not the case for the Hony vaporization of large amounts of water. The in- microtektites, which might well represent the best creased cloud cover which would result from this M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 143 would also insulate the Earth, preventing heat loss for an early Maastrichtian, very rapidŽ much less and thereby causing global warmingB ŽBennett and than 1 Ma. growth of an ice sheet and attendant Glasser, 1999, p. 11. . Ozone depletion caused by the glacio-eustatic lowering has been recently presented impact can result in elevated UV-B radiation on the by Miller et al.Ž. 1999 . The sudden growth and surface of the Earth acting as a kill mechanism decay of an Earliest Famennian ice sheet might have Ž.Cockell, 1999 . Each of these mechanisms might been the result of the reduction and later, increase in result in the death of both the phytoplankton of greenhouse capacity of the atmosphere as the conse- oceans and plant life on land, but we know now that quence of sudden changes in the mode of ocean- it was not the case near the FFB. atmosphere operationŽ. Broecker and Denton, 1989 . The exceptional chitinozoan concentration in the KegelŽ. 1953 was the first to demonstrate the basal-most Famennian bed in La SerreŽ Paris et al., glacial origin of diamictite beds with faceted and 1996, fig. 2, partially reproduced here as Fig. 15. fits striated clasts in the Upper Devonian of the ParnaõbaÂ rather well the global cooling hypothesis as cold Basin, northern Brazil. MalzahnŽ. 1957 described water seems to have been more favorable for the striated pavements on sandstones then attributed to proliferation of these microfossilsŽ Paris et al., 1996, the Pimenteira Formation in the southeastern sector p. 143.Ž. . A very short glaciation would explain the of the same basin in the Piaui State. AThere is, sudden and short, major eustatic fall shown at the therefore, unequivocal evidence for widespread con- end of the T-R cycle IIdŽ. Fig. 21 of Johnson et al. tinental glaciation in one area belonging to the east- Ž.1985 . Short-term glacial phases during a Awarm ern half of the ParnaõbaÂ BasinB ŽBoucot, 1988, p. modeB period are known in the Paleozoic and in the 222. but the latter author added that the timing of Mesozoic. Brenchley et al.Ž. 1994 demonstrate this event was rather imprecise. Indeed, according to bathymetric and isotopic evidence for a short-lived Rocha-CamposŽ. 1981 , the diamictites and associ- Ž.0.5±1 Ma Late Ordovician glaciation in a Awarm ated rocks of alleged glacial origin in the ParnaõbaÂ modeB period. Even in the Late Cretaceous, which is Basin, which were partly maintained in the Pi- often presented as a good example of an ice-free menteira Formation by Andrade and DaemonŽ. 1974 , world, isotopic and sequence stratigraphic evidence were placed in the overlying CabecËas Formation by Carozzi et al.Ž. 1975 . This became an important distinction since Loboziak et al.Ž. 1992, fig. 4 have suggestedŽ. Fig. 22 , based on new palynological evidence, that most of the Famennian might be missing between the Latest Frasnian±Earliest Fa- mennian strata of the upper Pimenteira Formation and the Latest Famennian CabecËas Formation. Later, in 1996, one of usŽ. J.H.G.M. has been in the same area studied by MalzahnŽ. 1957 and could verify that the striated pavements are covered with tillites, and these latter covered by transgressive marine silt- stones and sandstones belonging to the LongaÂ For- mation, thus confirming, on the basis of lithological arguments, that the tillites do belong to the topmost Ž. Fig. 21. The Devonian sea-level curve of Johnson et al.Ž. 1985 CabecËas Formation see also Caputo, 1985 . There- from HallamŽ 1992, modified. Used with the permission of the fore, the glaciation evidence from the southeastern author. . Sub-stages of the Famennian after Fig. 6. A major ParnaõbaÂ Basin is probably not of the Latest Fras- eustatic fall is shown at the end of the T-R cycle IId. A domi- nian±Earliest Famennian age. nantly transgressive curve characterizes the lower half of T-R The recent discovery of dropstones in the Col- cycle IIe. A dominantly regressive curve characterizes the upper Ž. half of T-R cycle IIe. A widespread transgression culminates pacuchu Formation of the Peru±Bolivia Altiplano within the T-R cycle IIf while the important glacio-eustatic fall at Basin assumed by Isaacson et al.Ž. 1999, p. 241 to the end of the Famennian is only suggested. belong to Alate Frasnian and early FamennianB after 144 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 22. Comparison of ParnaõbaÂ Basin former stratigraphic schemeŽ. 1 , after Caputo Ž 1985 . , with new results Ž. 2 , from the central-western parts of the ParnaõbaÂ Basin, Brazil, after Loboziak et al.Ž.Ž.Ž. 1992, fig. 4 modified . A chronostratigraphy; B biostratigraphy after Daemon Ž.Ž.1974 ; C biostratigraphy after Loboziak et al. Ž. 1992 and unpublished data from S. Loboziak and J.H.G. Melo; Ž. D lithostratigraphy. Most of the Famennian might be missing between the Latest Frasnian±Earliest Famennian strata of the upper Pimenteira Formation and the Latest Famennian CabecËas Formation.

Racheboeuf et al.Ž. 1993 is not correctly dated. However, despite the fact that there is no palyno- Indeed, this formation is said by the latter authors to logical evidence for a glaciation of the Latest Fras- correspond to the late Frasnian Aat leastB, on the nian±Earliest Famennian age, one can wonder base of an acritarch species Ž.Maranhites insulatus whether a very short glaciation period, as suggested found in one sample from the Colpacuchu Formation by the very short eustatic fall duration, had any and known from the Frasnian to the Tournaisian in chances to be recorded by characteristic marine sedi- BrazilŽ. Racheboeuf et al., 1993, p. 801 . ments, because glacial deposition is commonly initi- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 145 ated by a recession of the ice at the end of the allow testing the rapid climatic change hypothesis on glaciationŽ Crowell, 1999; Crowell and Frakes, 1972; such an accurate scale. Visser, 1990, 1991. , and such deposits might well In order to explain the Late Frasnian diversity have been soon redistributed by the succeeding crisis, spanning at least 2.0 Ma, McGheeŽ. 1996 and transgression. The development of mountainŽ alpine RackiŽ. 1999 call upon a Amultiple impact theoryB. type. glaciers, not recorded at sea level, is another Several impacts would have affected, from time to possibility. time, the marine ecosystem by very short, rapid As noticed by Narkiewicz and HoffmanŽ 1989, p. climatic oscillationsŽ. not reaching the glacial level . 23. , the rate of eustatic sea-level change was so rapid However, the stability of land floras as deduced from immediately after the FFB that it cannot be ac- the miospore analysisŽ. see above does not confirm counted alone for by a mechanism referring to slow strong climatic oscillations during that entire interval down in spreading rates of oceanic ridge systems. of time. Instead, we must even admit a stable Late A glaciation would explain the abundance of Frasnian climate with the equatorial climatic belts chitinozoans at the basal-most Famennian of La Serre having reached a maximum width. section and why Athe hexactinellidsŽ. glass sponges Would the Late Frasnian diversity loss in migrate from deeper-water regions into the shallows miospores be rather the result of a warming trend of and undergo a burst of diversification in species the climate? Here comes back the volcanic hypothe- numberB across the FFBŽ. McGhee, 1996, p. 121 . sisŽ. Racki, 1998b . Example of volcanogenic rocks Modern glass sponges are indeed considered to be near the FFB may be found, for instance, in the east better adapted to cold waters than most other inverte- of the Pripyat DepressionŽ. Belarus in the upper part brate species. It would also explain why the Earliest of Evlanov Horizon and in Liven and Domanovichi Famennian low-latitude faunas were drastically re- Horizons, dated by miosporesŽ Obukhovskaya et al., duced and the diversity loss less severe in high-lati- in press. . The role of wildfire on land, initiated by tude regions. High-latitude faunas were less affected terrestrial volcanic activities, was important in car- as many species could simply have migrated to bon cycling since the Late DevonianŽ. Jones, 1999 . lower latitudes and so maintain their tolerable tem- Large amounts of CO2 from violent submarine vol- perature rangesŽ Copper, 1977, 1986, 1998; McGhee, canism might have caused long-term atmospheric 1996, p. 130. . Earliest Famennian global warming, warming, sea transgression and anoxia during the suggested by othersŽ Brand, 1989; Thompson and Late Frasnian. The anoxia may have been caused by Newton, 1988. would not explain the observed fau- the intrusion of the OMZ on epicontinental and shelf nal latitudinal zonations. basins of the world during sea transgressive pulses The diversity loss in pelagic fossil groups like Ž.Greenhouse effect, see also Caputo, 1994, 1995 . To conodonts and ammonoids might well be the result the thermal stress on land can be added the adverse of the rapidity of the climatic change itself that, after effects of volcanic poisons such as arsenic, fluorine Fisher and ArthurŽ. 1977 and also Crowley and and particularly chlorineŽ. Keith, 1982, p. 2632 . The NorthŽ. 1988 , may be the major trigger mechanism proposed volcanic warming might have also slowed of global ecosystem collapse. Such rapid climatic down the deep circulation of aerated polar waters change is well known in more recent time. For and developed stagnant ocean conditions increment- instance, several rapid temperature oscillations are ing the periodic development of anoxic conditions as recorded in the Middle Miocene of Pacific Ocean suggested by Wignall and TwitchettŽ. 1996, p. 1157 prior to the major onset of the Antarctic glaciation. for the end-Permian mass extinction. The character of the Middle Miocene isotopic record Such changes should be recorded by positive suggests that the Earth's climatic system became excursion of the d13C curve followed by negative extremely unstable and for perhaps 1 Ma oscillated excursion in marine sediments at the FFB. Unfortu- back and forth between glacial and interglacial modes nately, carbon isotope measurements in the related Ž.Woodruff et al., 1981, fig. 1 . Unfortunately, there timespan have given so far discordant resultsŽ Mc- exists so far no well-documented quantitative data on Ghee, 1996, p. 224. , but the inconsistency of pub- miospore successions across the FFB which would lished data might well be caused by imperfect bios- 146 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 tratigraphic definitions of the FFBŽ. Buggisch, 1991 . suggesting abrupt water turnover that might have Indeed, sedimentologic and isotopic carbon studies been caused by dense oxygenated polar water cur- carried out on stratigraphically well documented Late rents. Frasnian and Early Famennian strata in Austria, Buggisch'sŽ. 1991 model maintains that the Late France and GermanyŽ Joachimski and Buggisch, Devonian climate oscillated frequently between warm 1993. support the idea that an increasing positive and coldŽ. glacial phases and was, in fact, similar to excursion of the d13C, reflecting an increasing the variable climates of the Cenozoic. Such model biomass burial, corresponds to the UKW levelŽ up to cannot be entirely applied during the Late Frasnian q2.8½ over a Frasnian background value of q1½. . because supposed glacial phases are not matched by The same authors explain that the enhanced burial of regression trends in the Late Frasnian T-R cycles. It organic carbon may have a significant effect on the would apply, however, to the Earliest Famennian and

CO22 and O concentrations in the oceans and atmo- later to the Late and Latest Famennian.. Also, the sphere at the end of Frasnian time. AA lowering of oceanic overturn model of Wilde and BerryŽ 1984, the atmospheric CO2 concentration causes global 1986. suggesting a hypothetical sudden injection of climatic cooling and may result in a worldwide deep anoxic bottom waters into the normally aerated regression, if the icehouse effect is strong enough to waters of the shallow marine platform might explain initiate the buildup of polar ice capsB ŽJoachimski some loss of diversity in neritic species. However, and Buggisch, 1993, p. 677. . This negative d13C the phenomenon does not seem to have poisoned the anomaly is associated with an increase in d18 O upper part of water column since we know now that values. The very fast shift toward positive d18 O the plankton was not annihilated. It would not have values with an amplitude of about 2½ indicates a either any impact on the land floras. short-lived decrease in temperature of about 108C In conclusion, we suggest that atmospheric in- below the Latest Frasnian temperature in the Luoxiu crease of CO2 from violent volcanism might have section, South ChinaŽ. Zheng et al., 1993 , assuming caused long-term warming during the Late Frasnian that a 0.2½ increase in d18 O values represent a 18C and was succeeded by a very short-term glacial drop. This record supports the existence of polar ice phase in the Earliest Famennian. Each episode of the in the Earliest Famennian. d18 O values are driven crisisŽ. Late Frasnian to Earliest Famennian might primarily by a combination of glacio-eustatic sea indeed have been triggered by different factorsŽ Be- level and temperature. Therefore, the d18 O signal is nnett and Glasser, 1999. . Whether they were, at least a parameter available for estimating the magnitude partially, controlled by bolide impactŽ. s , volcanic and rate of change in sea level independently of paroxysm orŽ. and changes in CO22 and O concen- other geological recordsŽ. Williams, 1988 . The stable trations in the oceans and the atmosphere, short oxygen isotope values can add a new dimension cooling and glaciation seem the best reasonable ex- concerning timing, magnitude, and rates of sea-level planation for the major eustatic fall following the changes. The best estimate for this effect in the Kellwasser Event. How much time did the Pleistocene is a 0.11½ change for every 10 m of changeover take from the dysoxic conditions of the seawater removed. The change in d18 O through the UKW to the oxic and regressive phase of the Earliest FFB is q2½ in South China. This signal predicts a Famennian? Bratton et al.Ž. 1999 suggest that anoxia drop in sea level through the FFB of about 180 m. pre-dated the FFB by about 0.1 Ma, a timespan Part of this d18 O record must be due to temperature which, according to Sandberg et al.Ž. 1988, p. 297 and climatic deterioration, but this estimate compares might have been much shorter. with Issacson et al.Ž. 1999 estimates of 100±140 m drop in sea level during the Earliest Famennian. A major event of increased positive d34 S isotope values 7. The Early and Middle Famennian vegetation in sulfates, named the Soures eventŽ. Holser, 1977 , crisis indicates a prolonged anoxic interval with d34 Sq 30½ values in Late Frasnian time. The d34 S values In northwestern Canada, the Early Famennian and sharply decreased to q20½ at the Early Famennian the Earliest Middle Famennian are characterized by M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 147 six miospore zonesŽ. Fig. 9 and 10 first occurrences 22. , Early and Middle Famennian miospores are of taxaŽ. Braman and Hills, 1992, text-fig. 5 . In almost unknown and only a few miospore species, Early and Middle Famennian strata from eastern but none of the miospore zones cited above, have Europe, seven miospore zonesŽ. Fig. 10 are present, been recognized. The diversity loss of miospores, characterized by 29 first occurrencesŽ Avkhimovitch observed in the Late Frasnian, is obvious also in the et al., 1993, fig. 3. . A very characteristic Middle Early and Middle Famennian but becomes more and Famennian miospore assemblage, the Cornispora more severe from the paleo-tropical to the paleo-sub- Õaricornata Zone, is present all over Northern Eu- polar regions. A strong climatic gradient from a ramerica, dated by conodonts of the rhomboidea and warm equator to a cool pole was apparently operat- marginifera Zones. According to StreelŽ. 1986 , the ing during the Early and Middle FamennianŽ Streel, latitudinal distribution of this zoneŽ. Fig. 23 matches 1992. . the latitudinal distribution of Archaeoperisaccus in Global cooling, except probably in the equatorial the FrasnianŽ. Fig. 1 . belt, forced land plants to migrate from high latitudes By contrast, in the Early and Middle Famennian to lower latitudes but the available data do not record of southern Euramerica, only four, sometimes poorly this migration process. We must also keep in mind defined, miospore zones characterized by six first that the equatorial belt might well have kept its occurrences are known in western EuropeŽ Streel et moderate thermoperiodism, that is, the comparatively al., 1987. , and only two miospore Zones character- low level of environmental fluctuations, so that land ized by five first occurrences occur in eastern North plants which were not able to adapt to the moderate AmericaŽ. Richardson and Ahmed, 1988 . In western thermoperiodism had no other alternative than to Gondwana, i.e., in northern AfricaŽ Paris et al., collapse. The post-extinction Famennian recovery 1985.Ž and in Brazil Loboziak et al., 1992, and Fig. phase of marine faunas, Awhich looks less like a

Fig. 23. Paleophytogeographic distribution of the equatorial Middle Famennian miospore Cornispora Õaricornata Zone, after StreelŽ 1986, fig. 5.Ž. , based on the Middle Devonian map of Heckel and Witzke 1979 . The latitudinal distribution of this zone matches more or less the latitudinal distribution of Archaeoperissacus Ž.Fig. 1 , but data are scarce during the Middle Famennian and are even absents in Alaska and Siberia. 148 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 phase of explosive radiation but more like a long-term snow cover, because there was less midlatitude cy- recovery of 4±5 Ma featuring expansion of climati- clonic activity during the Late Devonian than in the cally more tolerantrresistant organismsB ŽCopper, modern worldŽ. McGhee, 1996, p. 134 . The same 1998, p. 139. is matched by an equally long-term phenomenon is locally matched today in the Barren period of poor development of land plants from Grounds in the Canadian NW Territories where the Ž.sub tropical Ž non-equatorial . to subpolar regions. climate is cold and dry with no ice and almost no This Early and Middle Famennian vegetation cri- vegetation cover. A glaciation may even require the sis is underlined by an unexpected phenomenon af- interaction of warm ocean currents, moisture-laden fecting the mean size of miospores that are signifi- warm air and cold winds generated by the glacial ice cantly smaller in the Famennian than in the Frasnian. itselfŽ. Brooks, 1949; Meyerhoff et al., 1996, p. 48 . This was demonstrated by NaumovaŽ. 1953 in the transitional Frasnian±Famennian beds of the Central Russian Platform, and also described by Becker et al. 8. The Late Famennian Ž.1974, enclosure II, fig. 3 for a widespread Late Devonian species closely related to the Ar- The Late Famennian starts with a major regres- chaeopteris miospore G. lemurata, namely Aneu- sion marking the end of carbonate-platform sedimen- rospora greggsii. The reduction of size is also mentation in many countries and the onset of continent- tioned by Richardson and McGregorŽ. 1986, p. 21 . wide erosionŽ Johnson et al., 1986; Thorez and The phenomenon is contemporaneous to the progres- Dreesen, 1997. . It corresponds to the start of the sive development in size of the megaspore, its reduc- upper half of T-R cycle IIe of Johnson et al.Ž. 1985 . tion in number within the megasporangium and, It is tempting to relate the major marine regressions later, the initialization of the first seeds. It is of a of the upper half of the T-R cycle IIeŽ. Fig. 21 with different nature than the reduction in size of the ice volume buildup on Gondwana despite the ab- conodont Palmatolepis observed by Renaud and Gi- sence of recorded glacigenic sediments at that time. rardŽ. 1999 across the FFB and the small phenotypes Probably, mountainŽ. alpine type glaciers were then of brachiopods occurring in the post-Kellwasser developing which are not recorded at sea level EventŽ. Balinski, 1996 . These are ephemeral phe- Ž.Sablock, 1993 . Crowell and Frakes Ž. 1970, fig. 7 nomena of organisms living in physiologically highly have very well explained the many factors that inter- stressed environmentsŽ the ALiliput effectB of Ur- play to bring about ice ages. banek, 1993. and seem to be a result of high juvenile From the start of the Late Famennian, miospore mortality and possibly stuntingŽ. Kammer, 1986 . diversity increases againŽ Raymond and Metz, 1995, The suggested Early and Middle Famennian al- fig. 3.Ž Fig. 8 . . The climatic gradient was probably most global cooling, which would explain the vege- less marked because the same miospore zones are tation crisis, is not matched by a major regression of recorded againŽ. like in the Frasnian from paleo- the sea level. Instead, Johnson et al.Ž. 1985 show tropical to paleo-subpolar regions, in the Peru± Ž.Fig. 21 a dominantly transgressive curve in the BolivianŽ.Ž Subandean Basin Perez-Leyton, 1991 . lower half of their T-R cycle IIe. Except for the and in the Amazon BasinŽ Loboziak et al., 1993; noticeable regression at the base, only minorŽ. if any Melo et al., 1996 and Fig. 24. , as in western Europe glacial phases are required for that part of the Fa- Ž.Maziane et al., 1999 . Additionally, the paleo-tropi- mennian. Indeed, cooling does not mean glaciation cal miospore zones have greater affinities than be- which requires, first of all, heavy snow fall. Now fore with the paleo-equatorial miospore zonesŽ e.g., Orminston and KlapperŽ. 1992 and Ormiston and all regions show the development of the Diducites OglesbyŽ. 1995 maintain that there was no perennial assemblages, Avkhimovitch et al., 1993, p. 90. . snow cover even in the high latitudes of Gondwana In the paleo-tropical Late Famennian of Virginia during the Late Devonian, in spite of projected win- and West VirginiaŽ. USA , on the western side of the ter land temperatures as low as y408C. This was Acadian Mountains, a peat-forming vascular plant dueŽ. according to their model to the lack of suffi- community occurs for the first timeŽ Scheckler, 1986; cient polar transport of moisture to form extensive Retallack et al., 1996. . Quantitative palynology of M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 149

sea-level fluctuation. Their regression or expansion are first controlled by dry versus wet climates. Wet climates produce flooding episodes that, in turn, carry more upland miospores into the sea basin. Streel and SchecklerŽ. 1990 conducted detailed analyses on the eastern side of the Acadian Mountains in a shallow epicontinental sea bordering the southern part of the Old Red ContinentŽ in the Ourthe Valley in southeast Belgium. . They suggest that recurrence of high sea levels, on one hand, and wet climates, on another hand,Ž. Fig. 26 are independent sixth-order cycles, i.e., about 30±40 ka in durationŽ Streel,

Fig. 24. Occurrence of the Late Famennian miospore Õersabilis ± cornuta ZoneŽ. VCo in the Barreirinha Formation of the borehole 2-MN-1-AM, Amazon Basin, Brazil, after Melo et al.Ž 1996, fig. 1 redrawn.Ž. . A Lithologic log; Ž. B cores and depth of lithostratigraphic boundaries;Ž. C lithostratigraphic units; Ž. D biostratigraphy;Ž. E inferred age. autochthonous sediments is now possible. It allows to recognize thereŽ. Fig. 25 different swamp and near-swamp characteristic. DownstreamŽ coastal lowland. AcoalB swamp and swamp margin environments are characterized, respectively, by Diducites Ž.D. plicabilis and Vallatisporites Ž V. hystricosus . miosporesŽ. Streel and Scheckler, 1990 . They are directly controlled by the short-term sea-level changes: any high sea-level phase will induce a high fresh-water table in those environments and therefore increase their importance by means of a higher proportion of their miospores in neighboring seas. PoumotŽ. 1989 demonstrates palynocycles in the tropical Neogene of the Gulf of Guinea and in Southeast Asia where the variation of the littoral flora indicates eustatic events, highstands of sea level Fig. 25. Late and Latest Famennian specific continental environments, after StreelŽ. 1999 . Miospore characteristics after Streel corresponding to the extension of the coastal lowland and SchecklerŽ. 1990 , Jarvis Ž. 1992 , Dreesen et al. Ž. 1993 . Well- swamps. drained alluvial plains: Aneurospora greggsii Žprobably Ar- The upstreamŽ. upland AcoalB swamp is also char- chaeopteris microspore. . Upstream and downstream ACoalB acterized by D. plicabilis but upstream swamp mar- swamps: Diducites plicabilis ± Auroraspora Õaria Complex Ž. gin environments are characterized by other taxa Rhacophyton isospore . Upstream swamp margins: Grandispora gracilis, Apiculiretusispora coniferus. Downstream swamp mar- Ži.e., Grandispora gracilis and Apiculiretusispora gins: Vallatisporites hystricosus, Auroraspora asperella, Retispora coniferus.. They are not directly affected by the lepidophyta. 150 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 26. Quantitative palynology in the upper part of the Esneux-railway sectionŽ Late Famennian, Evieux Formation, Ourthe Valley, Belgium.Ž , after Streel 1999, fig. 3. Used with permission of the Geologische Bundesanstalt of Austria. . Lithology and types of deposits after LafleurŽ. 1991 . The analysis of types of deposit illustrates a sequence of high frequency Ž fifth order cycle . of about 0.1 Ma Ž Lafleur, 1991. . Recurrence of high sea-levels, on one hand, and wet climates, on another handŽ both inferred from quantitative analysis of characteristic miospores. are believed to correspond to independent sixth-order cycles, i.e., about 30±40 ka in duration.

1999. . They demonstrate also that this shallow epi- expansion of downstreamŽ. coastal lowland swamps continental sea received major floods from local and explain the growing affinities between paleo- rivers. tropical and paleo-equatorial floras. In the high latitudes, the Late Famennian climate Seed plants appear in the Late Famennian was probably less cold than before but probably Ž.Fairon-Demaret and Scheckler, 1987 . The differen- wetter, allowing snowfall on the mountains and veg- tiation of the seed was a key innovation in early land etation in the lowlands. VallatisporitesŽ V. hystrico- plant evolution, facilitating exploitation of a range of sus, V. sp. cf. V. anthoideus. are characteristic species environments and ecological strategiesŽ. Sims, 1999 . of these lowland vegetations in regressive marine After a first occurrence in Frasnian time and a long strata of the Late Famennian Upper Barreirinha and gap of record comprising most of the Famennian Lower Curiri Formations of the Amazon Basin in Ž.McGhee, 1996, p. 87 , tetrapods AreinvadedB the BrazilŽ. Loboziak et al., 1997a . Therefore, they might land. They are dated by miospores as AFa2bB in well derive from coastal lowland swamp margin GreenlandŽ. Marshall et al., 1999 , and AFa2cB in environments bordering the marine basin. In low PennsylvaniaŽ. Cressler and Daeschler, 1999 . latitudes, paleovertisols in Fa2c of the paleo-tropical If the major marine regressions of the upper half Catskill Formation indicate a seasonally wet-and-dry of T-R cycle IIe are related with ice volume buildup climateŽ. Bambach et al., 1999 . Potential monsoonal on Gondwana, then the Buggisch'sŽ. 1991 model, circulation pattern makes the climate in the deep with warm phases alternating with glacial phases, tropics more savannah-like than everwet tropical. can now be applied. A cyclic operation process However, the development in the low latitudes of the might have developed with the following succession: Diducites assemblages might well reflect also the transgression Ð high organic production Ð deposi- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 151 tion and high preservation of organic carbon Ð 1978. . Now, the coastal lowland vegetation that lowering of CO2 in the atmosphere and ocean Ð produces R. lepidophyta has a worldwide distribu- icehouse effect Ð polarŽ. alpine type glaciation Ð tionŽ. Byvsheva et al., 1984 from sub-polar to equa- regression Ð erosion and low preservation of or- torial regionsŽ. Fig. 28 . The climate had become less ganic carbon and resupply of CO2 to the ocean and cold in high latitudes but wetter than before probably atmosphere Ð greenhouse effect Ð deglaciation Ð because the midlatitude cyclonic activity allowed transgression. sufficient polar transportation of moisture to form large snow cover. Extensive coastal glaciersŽ Caputo, 1985, 1994; Caputo and Crowell, 1985; Diaz et al., 9. The Latest Famennian() Strunian 1999. developed in different Bolivian and Brazilian Basins, well dated by miosporesŽ Perez-Leyton, 1991; The early Latest Famennian starts with a Loboziak et al., 1992, 1993, 1997b and Fig. 29; Diaz widespread transgressionŽ. Fig. 21 which could cor- et al., 1993a,b, VavrdovaÂ et al., 1991, 1993, 1996. . respond to the melting phases of the hypothetical BarÈ and RiegelŽ. 1974 have also pointed the exact Late Famennian mountain glaciers. The miospore lithofacies similarity between the LongaÂ Formation zones are characterized by the incoming of Retispora in the ParnaõbaÂ Basin of Brazil and the Ghanean lepidophyta which belongs, together with Val- Takoradi Shales of probable glacial origin, in west- latisporites hystricosus, to the coastal lowland swamp ern Africa. The late Latest Famennian age and the margin environmentsŽ. Streel, 1999 and is directly correlation between Brazil and Ghana has been con- controlled by sea-level changes. The coastal lowland firmed by MazianeŽ. 1997 who demonstrated that miospore assemblage containing R. lepidophyta Žthe even the important reworked part of the miospore R. lepidophyta±K. literatus or LL Zone. dominates assemblages were almost identical in both regions. both the paleo-equatorial and the paleo-tropical re- One of usŽ. M.V.C. has studied samples from the gions. The miospore zone and most of the species Tahara Formation in the A.1-NC 58 wildcat well at are now the same in both regionsŽ Avkhimovitch et the central Murzuq BasinŽ. Libya , near the Algerian al., 1988a,b. , but these assemblages are missing in and Nigerian borders. Study results indicate that the sub-polar western Gondwana. In the Amazon Basin Tahara Formation, at that locality, contains diamic- Ž.Fig. 27 , for instance, there is a miospore gap tite, conglomerate, sandstone and shale interbeds. Ž.sediment palynologically barren between the Late The glacial nature of the diamictites was inferred Famennian upper Barreirinha and lowest Cururi beds from their rock textures. The occurrence of R. lepi- and the late Latest Famennian upper Cururi with dophyta in the Tahara FormationŽ Coquel and glacio-marine sedimentsŽ Loboziak et al., 1996, p. Moreau-Benoit, 1986. dates the diamictite suggest- 211 and 1997b, p. 39; Melo et al., 1996, fig. 1. . It ing that the Latest Famennian glaciation might have might be the result of a new but short-term, cold and reached southern Libya. dry phase in sub-polar region where the absence of There are no other, biostratigraphically controlled, snowfall does not allow mountain glaciers to de- Late Devonian glacial deposits in Africa. The Niger velop. With the transgression, major changes occur tillites mentioned by Scotese et al.Ž. 1999, p. 110 is in several fossil groups like the Rugosa, which radi- only known as Aolder than ViseanÂ B ŽLang et al., ates again after their decline during the Late Frasnian 1991. and the so-called Devonian±Carboniferous Ž.Poty, 1999 . MambereÂÂ Formation from central AfricaŽ cited by The late Latest Famennian starts with the first Isaacson et al., 1999, p. 241. is only indirectly dated occurrence of an almost cosmopolitan, but not abun- by paleomagnetic observations according to which dant miospore species, Indotriradites explanatus Žthe the pole Ais close to Middle Devonian±Lower Car- R. lepidophyta±I. explanatus or LE Zone. , suc- boniferous polesB Ž.Censier et al., 1995, p. 24 . ceeded by Verrucosiporites nitidus Ž the R. lepido- Available evidence of glaciation includes diamic- phyta±V. nitidus or LN Zone. accompanied by a tites with striated, faceted and polished pebbles; Vallatisporites species Ž.V. Õallatus probably evolved rhythmites with dropstones; erratic boulders, striated from the former V. hystricosus ŽStreel and Traverse, pavements, and glacially deformed sedimentary rocks 152 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 27. Gap in the Latest Famennian succession of the Amazon Basin, Brazil, after Loboziak et al.Ž. 1996, fig. 1 modified and Loboziak et al.Ž 1997b . . Palynozones: Ž. 1 after Streel et al., 1987, Streel and Loboziak, 1996, Maziane et al., 1999; Ž. 2 modified from Daemon and ContreirasŽ. 1971 and Daemon Ž 1974, 1976 . . Lithostratigraphy Ž. 3 modified from Caputo Ž. 1985 . In the Amazon Basin, the miospore gap Ž.sediment palynologically barren occurs between the Late Famennian upper Barreirinha and lowest Cururi beds and the late Latest Famennian upper Cururi with glacimarine sedimentsŽ. Loboziak et al., 1996, p. 211 and 1997b, p. 39; Melo et al., 1996, fig. 1 . It might be the result of a new but short-term, cold and dry phase in sub-polar region where the absence of snowfall does not allow mountain glaciers to develop.

Ž.sandstone and lodgment tillites . These diamictites during this timespan in the hinterland of the Latest usually contain a large amountŽ often, over 50% of Famennian high latitudes. Some rhythmitesŽ see Ca- the total assemblage. of reworked miospores from puto, 1985, fig. 13 or Caputo and Crowell, 1985, Givetian and Frasnian assemblages. This reworked fig. 11.Ž proved to be real varves Streel et al., in material, which is very well preserved, is recogniz- press. . They contain species belonging to a high able only by its stratigraphic range known elsewhere. stratigraphic position within the Latest Famennian The most recent reworked miospores belong to the Ž.the LN Zone , but presenting a different quantitative Late Frasnian Zone AIVB. No reworked miospores composition in alternating sandy and silty laminites. from Early to Late Famennian can be demonstrated Sandy layers were probably first settled after the which confirms that sparse vegetation was present local seasonal melting of the ice cover and the rush M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 153

Fig. 28. Paleophytogeographic distribution of the Latest Famennian miospore R. lepidophyta, after StreelŽ. 1986, fig. 6 , based on the Middle Devonian map of Heckel and WitzkeŽ. 1979 . The worldwide distribution of R. lepidophyta is obvious Ž no data available from Siberia for that period of time. . This species is produced near the deposition site explaining its exceptional abundance in most localities. The vegetation represented by these assemblages is believed to be cosmopolitan coastal lowland vegetation which depends more on a local moisture and equable climate than on the maybe adverse climates of distant hinterland areas. of fresh water supply, the silty layers being deposited During the Latest Famennian, the climate was, when the spring water run-off decreases. thus, cold in the high latitudes but probably warmer

Fig. 29. Age assignmentŽ. Late Famennian to Tournaisian and biostratigraphic correlation between Amazon and ParnaõbaÂ Basins, Brazil, after Loboziak et al.Ž 1993, fig. 5 modified with unpublished data from S. Loboziak and J.H.G. Melo. .) Miospore Zonation after Streel et al.Ž. 1987 , Higgs et al. Ž. 1988 and Maziane et al. Ž. 1999 . The undifferentiated lepidophyta±explanatus? and lepidophyta±nitidus ŽLE?±LN . Zones are known with diamictites from many boreholes of the Amazon and ParnaõbaÂ Basins. 154 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 than before in the intertropical regions. Valentine glaciers and the simultaneous extension of the arid Ž.1984, fig. 1 gave broad-scale paleotemperature es- tropical belt might have confined the intertropical timates for low latitudes and high latitudes during convergence zoneŽ the belt of low level of environ- the Cenozoic which clearly show that oceans in the mental fluctuations. to a narrow latitudinal, and per- late NeogeneŽ during the onset of the Antarctic haps discontinuous, range surrounding the equator, a glaciation. were significantly cool in high latitudes situation comparable to what happened during the but warmer than before in low latitudes. Similarly, Pleistocene Late Glacial Maximum. But it was prob- Raymond et al.Ž. 1989 suggested that high latitude ably not a permanent situation because we know that cooling and equatorial warming between the Na- rapid climatic changes also characterize the onset of murian A and B may have been caused by the onset glaciation. The cyclic nature of climate allowed even of glaciation in the Southern Hemisphere. Data given intertropical marine faunas to reach occasionally the by BrandŽ. 1993, fig. 3 , based on isotopic studies of subpolar areas during climatic temperate phases, as brachiopod shell material, indicate that temperatures indicated for instance by the occurrence, in South in the Latest Famennian ranged from 32±388C in the America, of the Latest Famennian cephalopod Wock- equatorial belt to 17±188C only in the subtropical lumeria Ž.Becker, 1993; House, 1996 . beltŽ. Fig. 30 . Even accepting adjustments Ž Brand, Wide latitudinal gradient of temperatures and 1989, p. 321. to bring such values into Arealistic quick cyclic climatic changes might well be consid- environmental and biological conditionsB would not ered unsuitable conditions for the cosmopolitan char- change much the picture that the latitudinal gradient acter of the end-Famennian vegetation. One must of temperatures was important during the Latest remember, however, that this vegetation is only Famennian. It seems that the development of polar known through the filter of transport processes carry-

Fig. 30. Model of water temperatures of AglobalB Famennian seawater based on calculations of oxygen isotope data after isotopic studies of brachiopod shell material made by BrandŽ. 1993 . Base map: Middle Devonian map of Heckel and Witzke Ž. 1979 . Data indicate that temperatures in the Latest Famennian ranged from 32±388C in the equatorial belt to 17±188C only in the subtropical belt. Even accepting adjustmentsŽ. Brand, 1989, p. 321 to bring such values into Arealistic environmental and biological conditionsB would not change much the picture that a qualitative latitudinal gradient of temperatures was important during the Latest Famennian. M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 155 ing miospores from their source area to the sea basin. the Hangenberg Event, at the family level. Land Now the Latest Famennian miospore assemblages plantsŽ.Ž Fairon-Demaret, 1986 , miospores Streel, have an unusual characteristic: the almost invariable 1986.Ž and acritarchs Vanguestaine, 1986 . show ob- dominance of one single species Ž.R. lepidophyta , vious important changes near the end of the Devo- which often constitutes more than 50% of all nian. However, these changes occur clearly above miospores present. This means that this species is the Hangenberg EventŽ. above the HBS , i.e., closer produced near the deposition site and that the vegeta- to the DCB. Indeed the base of the HBS corresponds tion represented by these assemblages is cosmopoli- to the base of the R. lepidophyta±V. nitidus or LN tan coastal lowland vegetation that depends more on miospore ZoneŽ. Higgs and Streel, 1994 , which, a local moisture and equable climate than on the except for a few added species, is very similar to the probably adverse climates of distant hinterland areas. former LL and LE Zones. Moreover, the occurrence The high proportion of coastal lowland vegetation of Devonian trees like Archaeopteris in Ireland miospores in the assemblages might be also a result Ž.Jarvis, 1992 and rich acritarch assemblages in the of the poor miospore production by a scarce vegeta- Riescheid section in SauerlandŽ. Weldon, 1997 are tion cover in these hinterland areas. coeval with the LN miospore Zone. Obviously, the major terrestrial event does not exactly coincide with the marine oneŽ in contradiction with the opinion of Hallam and Wignall, 1997, p. 74. . 10. The end-Famennian Crisis and the Hangen- The DevonianrCarboniferous Global Stratotype berg Event Section and PointŽ. GSSP has been fixed Ž Paproth et al., 1991.Ž in the La Serre Section Montagne Noire, By comparison with the first chapters of this southern France. at a level between the Siphonodella paper, concerned with the Late Frasnian to Early praesulcata and S. sulcata Zones of the standard Famennian 3 Ma timespan, it is unnecessary to conodont zonation. It is far from being an ideal discuss the end-Famennian events in separated chap- GSSPŽ. for instance it yields no palynomorphs and ters because it seems that they all occurred in a therefore Auxiliary Stratotypes SectionsŽ. ASS have rather short interval of time, perhaps only 0.1 Ma been designated in the SauerlandŽ. Germany and Ž.Sandberg and Ziegler, 1996 . The end-Famennian NambiancunŽ. China areas. The Stockum section, crisis is linked by most authors to the Hangenberg near the ASS of the Sauerland, displays a well-docu- EventŽ. Walliser, 1984 , defined at the base of the mented transition across the DCB. T-R cyclesŽ Bless Hangenberg Black ShaleŽ. HBS , in the Sauerland, et al., 1993, fig. 4. or holostratigraphic intervals Germany, on the top of the Wocklum Limestone, the Ž.Becker, 1996, table 2 and miospore quantitative uppermost part of which bears the poorly character- analyses of the Stockum sectionŽ. Fig. 31 allow ized Middle praesulcata conodont Zone and the LE subdividing, with detail, the rather short timespan miospore Zone. When the Late praesulcata con- between the Hangenberg Event and the DC Bound- odont Zone occurs in the Stockum Limestone, imme- ary. diately beneath the DCB, the extinction crisis is over. Although in the literature the Hangenberg Event 10.1. The Stockum section is not included in the Abig 5B bio-eventsŽ like the Late Frasnian Crisis. , it is one of the most severe In the HBSŽ. sample 162, Fig. 31 , the miospores bio-events in the Phanerozoic. Drastic mass extinc- are scarce but black homogeneous palynodebris are tion took place at that level, e.g., involving the abundant, corresponding to oxic conditions of the clymenid ammonoids and the hemipelagic and palynofaciesŽ. see below . In the overlying lower part pelagic ostracodesŽ. Walliser, 1995 . As many as of the Hangenberg Shales, miospores are abundant 21% of the marine genera and 16% of the marine and rather well preserved, palynodebris being more familiesŽ. Sepkoski, 1996 became extinct. Simakov heterogeneous and translucent than in the HBS. Ž.1993 even estimates about 20% extinction during Probably, the deposition of the Hangenberg Shales 156 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 was very rapid, preventing oxidation of the palyn- dant. In the upper part of the Hangenberg Shales and odebris. Here the coastal lowland swamp margin Sandstones and in the overlying Stockum Limestone, miospores Ž.V. hystricosus, R. lepidophyta are abun- sandstones are progressively more abundant and the M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 157 palynofacies return to oxic conditions. Coarser sedi- Sandberg and Ziegler'sŽ. 1996 opinion of a short ments and oxic conditions result probably from river time-rangeŽ. 0.1 Ma for the Middle praesulcata run-off after a wetter climatic development. Indeed, Zone. Consequently, the rate of sedimentation oper- upstream swamp margin miospores Ž.A. coniferus ating during the LN miospore Zone in the Sauerland become abundant and take over the R. lepidophyta was high compared to the rate observed during the dominance. The strong regression of the coastal low- VCo Zone in the Ourthe valley. In low latitudes, land swamp margin miospores and the almost com- higher sedimentation rate and sandy input should plete extinction of the AcoalB swamp miospore, D. correspond to wetter climate phases and increased plicabilis, suggest that this new, wet climatic condi- river supply during the Latest Famennian compared tion matched the lowest sea-level condition. These to the Late Famennian. probably adverse climatic and edaphic environmental Evidence of wetter climate may have started in changes strongly reduced the Latest Famennian the upper part of the Wocklum Limestone, i.e., in the coastal lowland swamp margin and AcoalB swamp Drewer SandstoneŽ. Fig. 32 . This would explain the vegetation. These plant communities completely dis- genesis of the overlying HBS in the Sauerland. After appear immediately below the Stockum Limestone Van SteenwinkelŽ. 1993, p. 678 , the HBS is a con- Ž.i.e., very near but below the DCB , being replaced densed unit created by sediment starvation and corre- by a new, poorly defined miospore Zone, the V. sponds to a worldwide event characterized, in the Õallatus±Retusotriletes incohatus or VI Zone where Sauerland area, by basinal condensation during a A. coniferus is abundant. maximum rate of eustatic sea-level rise. After Van At the level of sample 94, immediately above the SteenwinkelŽ. 1993 , it represents the condensed Lat- last sandstone horizon, very abundant acritarchs sud- est Devonian Transgressive and Highstand System denly occur, making 70% of the total palynomorphs TractsŽ. TST q HST of the previous sequence, Ž.miosporesqacritarchs . Surprisingly, the assem- whereas the Wocklum LimestoneŽ including the blage is composed of one single AspeciesB of Mi- Drewer Sandstone. corresponds to the underlying crhystridium, representing a first opportunistic bloom Lowstand System TractŽ. LST . During the deposition of one taxon after the ALatest Devonian extinctionB. of the upper part of the Wocklum Limestone, erosion At Stockum, it seems to coincide with the basal of organic soils and vegetation cover probably started Carboniferous eustatic rise. on the continent. Rivers discharged a large amount of sand, mud and organic matter into the sea. Except 10.2. The Sauerland area in some nearshore areas, like in the neighboring Riescheid locality where pre-LN shaly sediments are The cyclicity observed in quantitative palynology rather thick, this erosional material was then trans- above the Hangenberg Event in the Sauerland is ported by marine currents far offshore, the sand obviously of the same nature as the two kinds of being deposited first, as on the shoal of the Drewer cyclesŽ. change of sea level and of climate described areaŽ. Bless et al., 1993, fig. 3 , the mud and organic in the Late Famennian of the Ourthe valley, in matter bypassing the shoals to be deposited farther BelgiumŽ. Fig. 26 . Therefore, they probably corre- into the basin in the form of lowstand submarine spond to sixth-order cycles, adding some support to fans. Subsequently, during the next sea-level rise,

Fig. 31. Quantitative palynology in the Latest Famennian and Tournaisian Stockum trench II sectionŽ. Sauerland, Germany , after Streel Ž1999, fig. 4. Used with the permission of the Geologische Bundesanstalt of Austria. . Miospore Zonation and lithology after Higgs et al. Ž.1993, fig. 1 modified ; holostratigraphy after Becker Ž. 1996 . DCB is between samples 97 and 99 or between holostratigraphic intervals 13 and 14. Recurrence of high sea-levels and wet climatesŽ. both inferred from quantitative analysis of characteristic miospores are believed to correspond to sixth-order cycles, i.e., about 30±40 ka in duration, by comparison with data from the Late Famennian of BelgiumŽ. Fig. 26 , adding some support to Sandberg and Ziegler'sŽ. 1996 opinion of a short time-range Ž 0.1 Ma . for the Middle praesulcata Zone Ž see also Fig. 32. . 158 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Fig. 32. Synthesis of quantitative palynology and comparison with sedimentology and climatology in the Latest Famennian and Tournaisian sections of SauerlandŽ. Germany after Streel Ž 1999, fig. 5. Used with the permission of the Geologische Bundesanstalt of Austria. . Lithology has no scale. Holostratigraphic levelsŽ. Becker, 1996 allow comparing with the detailed lithology of section Stockum in Fig. 31. CrD: DevonianrCarboniferous Boundary or DCB. Glacial phases in Western GondwanaŽ. Brazil , dated by LE?±LN Zones, immediately preceded a very wet and, soon, colder climate in the southern tropical beltŽ. Sauerland .

together with the rise of the anoxic zone, upwelling regions present marine guide fossils and miospores or overturnŽ. Girard, 1994 could have spread the closely associated, and thus correlations are often too black mud almost all over the basin, except on the impreciseŽ for instance the incorrect association of nearshoreŽ. Riescheid area. Much as Pedersen and the LN Zone and Late praesulcata in Caplan and CalvertŽ. 1990, p. 463 , we believe that the propor- Bustin, 1999, figs. 2 and 3. . tion of organic matter of terrestrial vs. marine origin But the almost complete absence of acritarchs in black shales varies widely between locations, demonstrates that the HBS in the Sauerland was indicating in many cases the dominance of local or never deposited nearshore before being deposited regional factors rather than ocean-wide phenomena. farther into the basin and then redistributed by up- The perfect synchroneity of the HBS around the welling or overturn. Even leiospheres, which demon- world is far from being demonstrated because few strate a capability for surviving widespread extinc- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 159 tions of acritarchs at that stratigraphic level peak, probably as a consequence of an Earliest Tour- Ž.Olempska, 1997 , are almost, absent in the HBS. naisianŽ. Fig. 32 colder climate Ž Brand, 1989, 1993 . , Moreover, the impoverished miospore content and which could have extended even into low latitudes. the destruction of the thinner, more or less translu- What are the ultimate causes of the end-Famen- cent, heterogeneous debris of the palynofacies point nian glaciation? Was it, at least partly caused, by a out to extensive transportation into the sea prior to bolide impact, a volcanic paroxysm andror a change deposition in the anoxic zone. in CO22 and O concentrations in the oceans and Climatic changes across the DCB have been in- atmosphere also postulated for the hypothetical low- vestigated on the basis of brachiopod shell geochem- ermost Famennian glaciation? To our knowledge, no istryŽ Brand, 1989, 1993; Brand and Legrand-Blain, microtektites have been reported from near the DCB. 1993. . These authors note that it was not until the Iridium peaks are known in Austria, Canada, France latest part of the Latest Famennian that temperatures and China at the HBS or equivalent levelŽ Wang et started to decline in the low latitudes. Detailed con- al., 1993. , but they are interpreted as resulting from clusions, however, are hampered by the poor bios- a sudden change in paleo-redox conditions during tratigraphic resolution of studied horizons. Indeed, deposition andror diagenesis. Woodrow et al.Ž. 1990 no samples were tested which fit, without doubt, the show evidence of an impact-event in the Ap- HBS and Hangenberg Shales and Sandstones interval palachian BasinŽ. USA , near the DCB. The Spechty Ž.because they normally lack brachiopods . The Kopf Apolymictic diamictiteB would have been de- Wocklum Limestone is older. The Louisiana Lime- posited rapidly and all at once over 400 km and stone, in eastern MissouriŽ. USA and the AMiddle dated by the presence of the miospore R. lepido- siliciclastic calcareniteB in the AGriotte FormationB phyta Ž.McGhee, 1996, p. 187 . Unfortunately, it at La Serre might be slightly younger than the seems that the miospore assemblage, recovered in sequence under consideration as they are assumed of these sediments, did not allow using the very precise Late praesulcata AageB Ž.but see Girard, 1994 . Only correlation data existing between miospore and con- the basal, shaly part of the Alower ooliteB in the odont zonationsŽ. Streel et al., 1987 . Therefore, if Griotte Formation of La Serre might be an equiva- any correlation really exists between the Apolymictic lent of the Hangenberg ShalesŽ Bless et al., 1993; diamictiteB and an impact-event, it can only be Girard, 1994. . It is thus of some significance that assigned, in terms of conodont stratigraphy, to within temperature fall is only recorded higher than this the Late expansa±Late praesulcata interval. Evi- oolite, i.e., in the upper part of the Amiddle siliciclas- dence for highly explosive volcanism is found in the tic calcareniteB at La Serre, corresponding to the occurrence of the ABombenschalsteinB in the basal same level where, in the Sauerland, the LN Zone Wocklum Stufe of the Rhenish Massif. Also contain- definitively ended. ing a R. lepidophyta miospore assemblageŽ Somers The sea-level lowstand documented by, possibly, and Streel, 1978. , these sediments were, however, the topmost Wocklum Limestone and certainly the regarded as a Late expansa or Early praesulcata Hangenberg Sandstone corresponds to the develop- equivalentŽ. Dreesen, 1986, p. 35 , i.e., rather older ment of coastal glaciers in high latitudes because than the Hangenberg Event. A major, sudden nega- western Gondwanan glacio-marine sediments are tive excursion of the d13C curve, reflecting a de- demonstrated to contain perhaps the LE Zone but creasing biomass in the Muhua section in ChinaŽ Xu certainly the LN ZoneŽ According to Melo et al., et al., 1986. , is referred to the DCB event by Rampino 1999, supposed occurrences of the LE Zone in Brazil and HaggertyŽ. 1996, p. 20 but occurs much higher, might well correspond to an impoverished LN Zone. . i.e., at the base of the Tournaisian S. crenulata Miospore analyses in the tropical region, correspond- conodont Zone. Thus there is no evidence of any ing to the peak of the regression, point out to a bolide impact or volcanic paroxysm firmly related to wetter climate which has strongly modified the con- the Hangenberg Event. Buggisch'sŽ. 1991 model temporary AuplandB and Acoastal lowlandB plant Ž.Žsee the end of Section 8 , with warmer phases the communities. The Acoastal lowlandB communityŽ the equivalent of most of the Wocklum Limestone and lepidophytus complex. did not recover after that the HBS.Ž alternating with glacial phases the equiva- 160 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 lent of the Drewer Sandstone and the Hangenberg which is often characterized by condensation or Shale and Sandstone. can probably be applied. How- physical breaks in sedimentationŽ Ziegler and Klap- ever, it is true that, if the stratigraphy of the DCB per, 1985, p. 108. . The same point was taken into has been intensively studied during the two last account when defining the DCB at the base of the decades, geochemical and sedimentological data, on sulcata conodont ZoneŽ. Paproth and Streel, 1985 the contrary, are still rather scarce at that level rather than at the HBS level as recommended by compared with what is known for the FFB. WalliserŽ. 1984 . The subsequent change in favor of a FFB fixed at the base of the Early triangularis Zone Ž.Cowie et al., 1989 is rather unfortunate because it 11. Comparison of the Kellwasser and Hangen- places that boundary between the event and the berg Events with immediate post-events post-event, i.e., at a critical level, whereas the DCB Both the Kellwasser and the Hangenberg events remains fixed after the post-event. are generally admitted to represent dysoxic facies coinciding with a rapid transgression which reversed 12. Discussion subsequentlyŽ. the post-events into a major regression. Whether or not this eustatic fall might corre- The history of the Late Frasnian±Famennian cli- spond to a short glacial phase in the high latitudes mates based on palynomorph analyses is built on after the Kellwasser Event is still unknown, but it three postulates:Ž. 1 Euramerica at slightly lower certainly does after the Hangenberg Event. Alto- latitudes than generally accepted by most paleomag- gether events and subsequent post-events might have netic reconstructions;Ž. 2 a conodont time-scale ac- lasted about 0.1 Ma or even less. Changes in CO2 cepted as the most used available subdivision of and O2 concentrations in the oceans and the atmo- time; andŽ. 3 Late Devonian sea-level fluctuations sphere were probably the first cause of the rapid mainly governed by glacio-eustasy. The two first change of climate. At the PaleocenerEocene transi- postulates have been discussed in Sections 2 and 3 tion large perturbations in the global carbon cycle and there is no need to reopen the discussion here. have recently been demonstrated to last about the On the contrary, even the reality of some sea-level same short time rangeŽ. Norris and Rohl,È 1999 . fluctuations was challenged recently, i.e., by Hallam Possible coincidence of bolide impact andror vol- and WignallŽ. 1999 who minimize the existence of a canic paroxysm with the icehouse climate might major eustatic fall following the Kellwasser Event. have contributed to induce a short glacial phase in They base their argumentation on the failure to the high latitudes immediately after the rather warm detect regressive intervals in the FFB of Poland and period of the Latest Frasnian. At the end of the Morocco. However, many other independent evi- Famennian, however, the high latitudes were already dences support a worldwide drop in relative sea level cold when the climatic changeover allowed the glacial Ž.see for instance Muchez et al., 1996 . The regis- phase to reach the sea level. The hypothesis of an trated imprint of eustatic movements in the sediment extraterrestrial or volcanic contribution is then not does not depend only on their vertical range but necessary and, anyway, it is not supported by facts. depend also on their duration, a very short one in the The climatic contrast from the event to the post-event case of the FFB. Also, breaks which exist, close to was obviously greater in the first case than in the the FFB, in the involved Moroccan sequences second one. In both cases, however, it has not partic- Ž.Schindler, 1990 , may be alternatively interpreted to ularly affected the land flora and the phytoplankton, be of local importance onlyŽ Wendt and Belka, 1991, the end-Famennian vegetation crisis occurring later, p. 72. where the relative movements are also con- immediately below the Late praesulcata conodont trolled by block faultingŽ. see Wendt, 1985, p. 817 . Zone, i.e., beneath the DCB. Finely, if Narkiewicz and HoffmanŽ. 1989 found It is tempting to remark that the formerŽ. 1983 indeed no evidence for any major sea-level changes definition accepted for the FFB, the Middle triangu- in the late Frasnian record of the carbonate platform laris conodont Zone, had the advantage to be at of southern Poland, on the contrary, Devleeschouwer some distance higher than the major crisis interval, Ž.1999, p. 218 , using a sedimentologic approach and M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 161 magnetic susceptibility curves on the same sections nian and Famennian organic-rich shalesŽ Joachimski as above, conclude that the sequence stratigraphy and Buggisch, 1993. . The Karoo Basin in South model he has developed in Germany and in the Africa contains thick dark shale beds in the upper Montagne NoireŽ. Southern France can be applied Devonian and lower Carboniferous section of the also in southern Poland and shows a sequence Witterberg GroupŽ. Streel and Theron, 1999 . The boundary at the FFB. We believe therefore that the Frasnian basinal shales of the Canning Basin in model illustrated by Hallam and WignallŽ 1999, fig. Australia are also rich in organic matterŽ Playford et 11. showing Kellwasser crisis and post-crisis entirely al., 1989. . This deposition of worldwide anoxic shales enclosed in a transgressive phase is, to say the least, that sequestered a large amount of CO2 from the far too selective. atmosphere and sea water may have provoked anti- The Famennian global cooling is part of a long- greenhouse effects and cooling events in Famennian term eventŽ. Berner, 1990 with a sharp falloff in CO2 and Tournaisian timesŽ. Caputo, 1995 . values occurring in the interval of time from the BernerŽ. 1993 concluded that the massive burial Middle Devonian into the Early CarboniferousŽ Al- of sedimentary organic matterŽ. lignin during the geo et al., 1995.Ž. . Algeo and Scheckler 1998 and Carboniferous and Permian periods evidenced by the BernerŽ. 1999 show that it is the result of a massive abundance of coal of this age, amplified the large increase of land plant biomass which occurs in just drop in CO2 concentration in that time. This hypoth- 15 to 20 Ma in the Middle and Late Devonian. esis is worth for the mid-Carboniferous onward, but Another very important contributing factor for the it does not explain the more than 10 million years Famennian global cooling may have been the trans- icesheet-free at sea level in Gondwana from the ference of CO2 from the atmosphere and sea water Earliest Famennian to the mid-late Tournaisian times, to organic sediments during the Devonian time, when Devonian and Tournaisian coal reserves being far large amounts of anoxic shales were deposited in less important than later. It also does not explain Gondwana and Euramerica intracratonic and shelf older glaciation events when true forests did not basins due to the expansion of the oxygen-minimum exist. An alternative cause to explain the decreasing zone. The decrease in the CO2 atmospheric content CO2 atmospheric content may be found in major was caused by significant transgressive phases that transgressive cycles that increase the rate of organic increased the rate of organic matter burial. Brazilian matter burial. Continental phytomass production to- Frasnian and Famennian anoxic shales have a mod- day is three times as large as the oceanic production erate-to-highŽ. 1±15% content of organic matter in Ž.Walter, 1984 but the comparison was probably in the Amazon, Solimoes,ÄÂ Parnaõba and Parana Â intracra- favor of the oceanic production at the end of the tonic basins. In the United States and Canada, there Devonian. Marine organic matter preservation during are extensive occurrences of Middle Devonian to major transgressive anoxic events may have sur- Mississippian shales, partly euxinic, represented by passed continental phytomass preservation. For ex- the Chattanooga Shale and its equivalentsŽ Conant ample, the Cretaceous marine organic muds contain and Swanson, 1961; Geldsetzer et al., 1985. . In an order of magnitude more carbon than that in all Belgium, France and Germany, the Matagne Shale known reserves of coal and petroleumŽ. Keith, 1982 . and its correlatives were deposited with thin layers The burial of high amounts of organic matter may of Kellwasser Limestone, under anoxic conditions have caused climatic coolingŽ. Arthur et al., 1988 or during Frasnian time. The Timan-Pechora, Volga- glaciationŽ. Jeans et al., 1991 at the Cenoma- Ural and Peri-Caspian Paleozoic basins in the former nianrTuronian boundary. The preservation of large Soviet Union have high oil and gas production from amount of organic matter in sedimentary rocks pro- widespread rich organic shale beds of Frasnian and vokes global climatic cooling and may result in a Famennian agesŽ Ulmishek, 1982; Peterson and significant worldwide regression, if the icehouse ef- Clarke, 1983.Ž. . According to Kalvoda 1986 , a fect is strong enough to initiate the buildup of conti- large-scale anoxic environment was also present in nental glaciersŽ. the Buggisch's model as happened the Latest Famennian timeŽ. lower praesulcata Zone occasionally in late Devonian and early Carbonifer- in Moravia. MoroccoŽ. North Africa also has Fras- ous time. However, in most transgressive cycles, 162 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 glacial events are not developed because the volume adverse effects of diverse volcanic poisons. It would of organic shale deposition is not large enough to explain the minimum diversity of miospores occur- deplete atmospheric CO2 and trigger glaciation. From ring progressively in the Late Frasnian. The warming mid-Carboniferous time onward, the spread of forests episode might have also slowed down the deep and related organic soils to lowlands generated by circulation of aerated polar waters and developed low sea level due to the worldwide regression may stagnant ocean conditions incrementing the periodic have delayed recoveries in atmospheric CO2 content, development of anoxic conditions, e.g., the Latest leading to longer lasting glacial ages. Frasnian Kellwasser HorizonŽ. UKW .

13.2. The Earliest Famennian 13. Conclusions Even if glacial evidences are not known at that time, a shortŽ. 0.1 Ma? glaciation seems the best 13.1. The Latest GiÕetian±Frasnian reasonable explanation of the major eustatic fall following the Kellwasser Event. The sudden growth The comparison based on conodont correlations, and decay of a hypothetical Earliest Famennian ice between Givetian and most of the Frasnian miospore sheet can be explained by the reduction and, later assemblages from, respectively, northern and south- increase in greenhouse capacity of the atmosphere. ern Euramerica demonstrates a high taxonomic di- These changes in the atmospheric CO might have versity in the equatorial belt and much difference 2 provoked changes in the mode of ocean-atmosphere between equatorial andŽ. sub tropical vegetation Ž Fig. operation. It may also be partly controlled by a 33. . On the contrary, a similar vegetation pattern and volcanic paroxysm andror bolide impacts. Indeed, therefore probably compatible climatic conditions the Hony microtektites represent the best-known evi- are present from tropical to subpolar areas. This dence of the impact of extraterrestrial bodies on vegetation seems to have extended its range into Earth corresponding to the UKW, and they are im- high latitudes from the Givetian to the Frasnian. mediately followed by a regression, suggested by the Indeed characteristic miospores of medium to high quantitative analysis of acritarch assemblages. The latitudes of western Gondwana almost disappear at almost complete absence of acritarchs right at the the end of the Givetian Stage. This probably corre- FFB is explained by the sedimentary conditions, not sponds to the persistency of rather hot climates necessarily by a real extinction. Unfortunately, for during the Frasnian, culminating in the Latest Fras- the time being, no accurate miospore succession is nian when it is noted that the equatorial climatic belt known for certain across the FFB. reaches its maximum width. Atmospheric increase of CO2 derived from submarine and continental violent 13.3. The Early±Middle Famennian volcanism and high sea-level stands might have caused the long-term warming during the Late Fras- The diversity loss of miospores, observed in the nian. To the thermal stress on land can be added the Late Frasnian, is obvious also in the Early and

Fig. 33. Synthesis of quantitative palynology and comparison with climate from the Latest Givetian to the Latest Famennian in the Southern Hemisphere. Conodont Zone and chronology after Sandberg et al.Ž. 1997, Fig. 2 . Frasnian and Famennian: Ð narrow hatch pattern for equatorial vegetation; Ð wide hatch pattern for tropical to subpolar vegetation. Givetian vegetation: see Fig. 5. Euramerican miospore Zonations: after Braman and HillsŽ. 1992 for westnorthern America Ž W-N. Am. . ; after Avkhimovitch et al. Ž. 1993 for eastern Europe Ž.E-Eur. ; after Richardson and McGregor Ž. 1986 and Richardson and Ahmed Ž. 1988 for eastnorthern America Ž E-N.Am. . ; after Streel et al. Ž.1987 and Maziane et al. Ž. 1999 for western Europe Ž W-Eur. .Ž. . 1 Late Frasnian Crisis and Kellwasser Event; Ž. 2 Hangenberg Event. The chart is organized to display the changes of the vegetation pattern over the south hemisphere against conodont and miospore biozonations so that each event can be situated in time and space. Climate in highest latitudes is superposed to the vegetation data. Most often, only the symbols of the miospore zones are provided. Four miospore biozonations are given, all from Euramerica. The two biozonations from northern Euramerica seem very different, but this actually reflects two different schools of palynologyŽ. western world versus former USSR , rather than deep biotic divergence. The two biozonations from southern Euramerica are rather similar, one being more detailed than the other. In this paper, the most detailed one is used for the Gondwanan vegetation. M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 163

Middle Famennian but it becomes more and more regions. A strong climatic gradient from a warm severe from the paleo-tropical to the paleo-subpolar equator to a cool pole seems to be operating during 164 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 the Early and Middle Famennian. Cooling does not than before with the paleo-equatorial miospore zones. mean glaciation which needs, first of all, heavy snow In the paleo-tropical Late Famennian, a peat-forming fall. As the sea level remains rather high during this vascular plant community occurs for the first time timespan, the climate was probably cold but dry. and makes possible quantitative palynology of au- Global cooling, except probably in the equatorial tochthonous sediments allowing the recognition of belt, forced land plants to migrate from high latitudes different swamp and near-swamp characteristic to lower latitudes but the available data do not record miospores. In the high latitudes, the Late Famennian this migration process. The equatorial belt might climate was probably less cold than before but prob- well have kept its moderate thermoperiodism, i.e., ably wetter, causing snowfall on the mountains and the comparatively low level of environmental fluctu- vegetation growth in the lowlands. The conspicuous ations, so that land plants which were not able to latitudinal gradient of vegetation seems to attenuate adapt to the moderate thermoperiodism had no other but it might be above all the result of the develop- alternative than to collapse. ment in the low latitudes of coastal lowland vegeta- tionsŽ. coastal lowland swamps dependent on moist 13.4. The Late Famennian and equable local microclimates. Buggisch'sŽ. 1991 It is tempting to relate the major marine regres- model, with warm phases alternating with glacial sions starting in the Late Famennian with ice volume phases, is probably applicable for this interval. buildup on Gondwana despite the absence of recorded 13.5. The Latest Famennian glacigenic sediments at that time. Perhaps mountain Ž.alpine type glaciers were then developing which The early Latest Famennian starts with a are not recorded. From the start of the Late Famen- widespread transgression, which could correspond to nian, the diversity of miospores increased again. The the melting phases of the hypothetical Late Famen- strong climatic gradient of the Early±Middle Famen- nian mountain glaciers. It might be the result of a nian become less marked because the same miospore new but short-term, cold and dry phase in sub-polar zones are recorded againŽ. like in the Frasnian from region where the absence of snowfall does not allow paleo-tropical to paleo-subpolar regions. Addition- the mountain glaciers to develop. The miospore zones ally, these miospore zones have greater affinities are dependent of the coastal lowland swamp margin

Fig. 34. Latest Famennian glacially striated pavement from the CabecËas Formation of the ParnaõbaÂ BasinŽ. Northern Brazil . Located close to the Calembe village at about 11 km southward from the town of Canto do Buriti on the roadŽ. Br 324 to the town of Raimundo Nonato. M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 165 environments and are directly controlled by the Algeo, T.J., Scheckler, S.E., 1998. Terrestrial-marine teleconnec- changes in sea level. During the end-Famennian, the tions in the Devonian: links between the evolution of land coastal lowland vegetation has a worldwide distribu- plants, weathering processes, and marine anoxic events. Phil. Trans. R. Soc. Lond. B 353, 113±130. tion from sub-polar to equatorial regions. The cli- Algeo, T.J., Berner, R.A., Maynard, J.B., Scheckler, S.E., 1995. mate has become less cold in high latitudes but Late Devonian oceanic anoxic events and biotic crises: wetter than before probably because the midlatitude ArootedB in the evolution of vascular land plants? GSA Today cyclonic activity allows sufficient polar transporta- 5Ž. 3 , 63±66. tion of moisture to form large snow cover. Extensive Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous±Tertiary extinction. coastal glaciersŽ. Fig. 34 developed in different Boli- Science 208, 1095±1108. vian and Brazilian basins, well dated by miospores. Andrade, S.M., Daemon, R.F., 1974. Litoestratigrafia e bioestrati- During the Latest Famennian, the climate is, thus, grafia do flanco sudoeste da Bacia do ParnaõbaÂ Ž Devoniano e cold in the high latitudes but probably warmer than CarbonõferoÂ . . 28th Congr. Brasil. Geol., Porto Alegre, Anais, before in the intertropical regions. It seems that the vol. 2, pp. 129±137. Arthur, M.A., Dean, W.A., Pratt, L.M., 1988. Geochemical and development of polar glaciers might have confined climatic effects of increased marine organic carbon burial at the intertropical convergence zoneŽ the belt of low the CenomanianrTuronian boundary. Nature 355, 714±717. level of environmental fluctuations. to a narrow lati- Avkhimovitch, V.I., Byvsheva, T.V., Higgs, K., Streel, M., Um- tudinal, and perhaps discontinuous, range surround- nova, V.T., 1988a. Miospore systematics and stratigraphic ing the equator. But rapid climatic changes also correlation of Devonian±Carboniferous Boundary deposits in the European part of the USSR and western Europe. CFS, characterize the onset of glaciation. The cyclic nature Cour. Forschungsinst. Senckenberg 100, 169±191. of climate allowed even intertropical marine faunas Avkhimovitch, V.I., Nekryata, N.S., Obukhovskaya, T.G., 1988b. to reach occasionally the subpolar regions. The Devonian palynostratigraphy of the Pripyat Depression, coastal lowland vegetation dominates the miospore Byelorussia. In: McMillan, N.J., Embry, A.F., Glass, D.J. Ž. assemblages and it depends more on a local moisture Eds. , Devonian of the World. Can. Soc. Petrol. Geol. Mem. 14Ž. 3 , 559±566. and equable climate than on the climate from distant Avkhimovitch, V.I., Tchibrikova, E.V., Obukhovskaya, T.G., inner areas. Buggisch'sŽ. 1991 model, with warmer Nazarenko, A.M., Umnova, V.T., Raskatova, L.G., phasesŽ the equivalent of most of the Wocklum Mantsurova, V.N., Loboziak, S., Streel, M., 1993. Middle and Limestone and the HBS. alternating with glacial Upper Devonian miospore zonation of eastern Europe. Bull. Ž. phasesŽ the equivalent of the Drewer Sandstone and Cent. Rech. Expl. Prod. Elf-Aquitaine 17 1 , 79±147. Balinski, A., 1996. Frasnian±Famennian Brachiopod faunal ex- the Hangenberg Shale and Sandstone. , probably re- tinction dynamics: an example from southern Poland. In: mained applicable. For the plant kingdom, the crisis, Copper, P., Jisuo, J.Ž. Eds. , Brachiopods. Proc. Third Int. which follows the Hangenberg Event was more se- Brachiopod Congr., Sudbury, Canada, 2±5 Sept. 1995. A.A. vere than the Late Frasnian Crisis. Balkema, Rotterdam, pp. 319±324. Bambach, R.K., Algeo, T.J., Thorez, J., Witzke, B.G., 1999. Dynamics of Devonian paleogeography and paleoclimatic im- Acknowledgements plications for expanding Archaeopteris forests. XVI Int. Bot. Congr., St. Louis, USA. 13, Abstracts. We gratefully acknowledge discussions and ad- Bar,ÈÂÂÈ P., Riegel, W., 1974. Les microflores des series paleozoõques vices received from many researchers, particularly du GhanaŽ. Afrique occidentale et leurs relations paleofloris-Â Ž. from R. Thomas Becker and Art Boucot. We thank tiques. In: Sittler, C. Ed. , Palynologie et DeriveÂ des Conti- nents. Sci. Geol. Bull. 27Ž. 1±2 , 39±58. the reviewers J.E.A. Marshall and P.B. Wignall for Becker, G., Bless, M.J.M., Streel, M., Thorez, J., 1974. Palynol- constructive criticism of the manuscript. The authors ogy and ostracode distribution in the Upper Devonian and are indebted to Mme R. NetterŽ. Lille for her help in basal Dinantian of Belgium and their dependence on sedimen- the drawing of some figures. tary facies. Meded. Rijks Geol. Dienst, Nieuwe Ser.Ž. Neth. 25 Ž.2 , 9±99. Becker, R.T., 1993. Analysis of Ammonoid palaeogeography in References relation to the global HangenbergŽ. terminal Devonian and Lower Alum ShaleŽ. Middle Tournaisian events. Ann. Soc. Adams, J.M., Faure, H., Faure-Denard, L., McGlade, J.M., Wood- Geol. Belg. 115Ž. 2 , 459±473. ward, F.I., 1990. Increases in terrestrial carbon storage from Becker, R.T., 1996. New faunal records and holostratigraphic the Last Glacial Maximum to the present. Nature 348, 711± correlation of the Hasselbachtal DrC-Boundary Auxiliary 714. StratotypeŽ. Germany . Ann. Soc. Geol. Belg. 117 Ž. 1 , 19±45. 166 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Bennett, M.R., Glasser, N.F., 1999. Glacial Geology, Ice Sheets form near the Devonian±Carboniferous Boundary. CFS, Cour. and Landforms. Wiley, New York, 1996, 364 pp. Forschungsinst. Senckenberg 67, 37±45. Berner, R.A., 1990. Atmospheric carbon dioxide levels over Caplan, M.L., Bustin, R.M., 1999. Devonian±Carboniferous Phanerozoic time. Science 249, 1382±1386. Hangenberg mass extinction event, widespread organic-rich

Berner, R.A., 1993. Paleozoic atmospheric CO2 : importance of mudrock and anoxia: causes and consequences. Palaeogeogr., solar radiation and plant evolution. Science 236, 68±70. Palaeoclimatol., Palaeoecol. 148, 187±207. Berner, R.A., 1999. Plants, rock weathering, and Paleozoic cli- Caputo, M.V., 1985. Late Devonian glaciation in South America. mate change. XVI Int. Bot. Congr., St. Louis, USA. 161, Palaeogeogr., Palaeoclimatol., Palaeoecol. 51, 291±317.

Abstracts. Caputo, M.V., 1994. Atmospheric CO2 depletion as glaciation Bless, M.J.M., Becker, R.T., Higgs, K., Paproth, E., Streel, M., and biotic extinction agent: the Late Devonian±Early Car- 1993. Eustatic cycles around the Devonian±Carboniferous boniferous glacial examples. Bol. Resumos Expandidos Boundary and the sedimentary and fossil record in Sauerland SimposioÂÃ Geol. Amazonia, Soc. Bras. Geol. 4, 194±197. Ž.Federal Republic of Germany . Ann. Soc. Geol. Belg. 115 Caputo, M.V., 1995. Anti-greenhouse effect as a glaciation and Ž.2 , 689±702. biotic crisis triggering agent: the Late Devonian and Early Bouckaert, J., Mouravieff, A., Streel, M., Thorez, J., Ziegler, W., Carboniferous glacial cases. Acad. Bras. Cienc.Ž Rio de 1972. The Frasnian±Famennian Boundary in Belgium. Geol. Janeiro.Ž. . Resumo Comun. 67 3 , 390. Palaeontol. 6, 87±92. Caputo, M.V., Crowell, J.C., 1985. Migration of glacial centers Boucot, A.J., 1988. Devonian biogeography: an update. In: across Gondwana during Paleozoic Era. Geol. Soc. Am. Bull. McMillan, N.J., Embry, A.F., Glass, D.J.Ž. Eds. , Devonian of 96, 1020±1036. the World. Can. Soc. Petrol. Geol. Mem. 14Ž. 3 , 211±227. Carozzi, A.V., Falkenheim, F.U.H., Carneiro, R.G., Esteves, F.R., Boulter, M.C., Spicer, R.A., Thomas, B.A., 1998. Patterns of Contreiras, C.J.A., 1975. AnaliseÂÄ ambiental e evolucËao plant extinction from some palaeobotanical evidences. In: tectonicaÃÄÂ sinsedimentar da secËao siluro-eocarbonõfera da Bacia Larwood, G.P.Ž. Ed. , Extinction and Survival in the Fossil do Maranhao.ÄÂ PetrobrasrCenpes, Ciencia-Tecnica-Petroleo; ÃÂÂ Record. Syst. Assoc. Spec. Vol. 34, 1±36. SecËao:Ä Explor. Petrol. 7, 1±48, qappendix. Braman, D.R., Hills, L.V., 1992. Upper Devonian and Lower Casier, J-G., Devleeschouwer, X., 1995. ArgumentsŽ. Ostracodes Carboniferous miospores, western District of Mackenzie and pour une regressionÂÁÂ culminant a proximite de la limite Fras- Yukon Territory, Canada. Palaeontogr. Can. 8, 1±97. nien-Famennien. Bull. Inst. R. Sci. Nat. Belg., Sci. Terre 65, Brand, U., 1989. Global climatic changes during the Devonian± 51±68. Mississippian: stable isotope biogeochemistry of brachiopods. Censier, C., Henry, B., Horen, H., Lang, J., 1995. Age devono-Â Palaeogeogr., Palaeoclimatol., Palaeoecol. 75, 311±329. carbonifereÁÂÂÂ de la formation glaciaire de la MambereŽ Repub- Brand, U., 1993. Global perspective of Famennian±Tournaisian lique Centrafricaine. : arguments paleomagnetiquesÂÂ et geolo- Â oceanography: geochemical analysis of brachiopods. Ann. Soc. giques. Bull. Soc. Geol. France 166Ž. 1 , 23±35. Geol. Belg. 115Ž. 2 , 491±496. Claeys, P., 1993. Geochemical and Sedimentological Record of Brand, U., Legrand-Blain, M., 1993. Paleoecology and biogeo- Impact Events in Earth History: Examples from the Late chemistry of Brachiopods from the Devonian±Carboniferous Pliocene, Cretaceous±Tertiary Boundary and Frasnian± boundary interval of the Griotte Formation, La Serre, Mon- Famennian Boundary. Ph.D. Thesis, Univ. California-Davis. tagne noire, France. Ann. Soc. Geol. Belg. 115Ž. 2 , 497±505. Claeys, P., Casier, J.G., Margolis, S.V., 1992. Microtektite glass Bratton, J.F., Berry, W.B.N., Morrow, J.R., 1999. Anoxia pre-dates at the FrasnianrFamennian boundary in Belgium: evidence for Frasnian±Famennian boundary mass extinction horizon in the an asteroid impact. Science 257, 1102±1104. Great Basin, USA. Palaeogeogr., Palaeoclimatol., Palaeoecol. Claeys, P., Kyte, F.T., Casier, J.G., 1994. Frasnian±Famennian 154, 275±292. Boundary Mass extinction, anoxic oceans, microtektite layers, Brenchley, P.J., Marshall, J.D., Carden, G.A.F., Robertson, but not much Iridium? LPI Contrib. 825, 22±24. D.B.R., Long, D.G.F., Meidla, T., Hints, L., Anderson, T.F., Claeys, P., Kyte, F.T., Herbosch, A., Casier, J.-G., 1996. Geo- 1994. Bathymetric and isotopic evidence for a short-lived Late chemistry of the Frasnian±Famennian boundary in Belgium: Ordovician glaciation in a greenhouse period. Geology 22, mass extinction, anoxic oceans and microtektite layer, but not 295±298. much iridium. In: Ryder, G., Fastovsky, D., Gartner, S.Ž. Eds. , Broecker, W.S., Denton, G.H., 1989. The role of ocean±atmo- The Cretaceous±Tertiary Event and Other Catastrophes in sphere reorganizations in glacial cycles. Geochim. Cos- Earth History, Boulder, Colorado. Spec. Pap.-Geol. Soc. Am. mochim. Acta 53, 2465±2501. vol. 307, pp. 491±504. Brooks, C.E.P., 1949. Climate Through the Ages. rev. edn. Mc- Claoue-Long,Â J.C., Jones, P.J., Roberts, J., Maxwell, S., 1992. Graw-Hill, New York, 395 pp. The numerical age of the Devonian±Carboniferous boundary. Buggisch, W., 1991. The global Frasnian±Famennian AKellwasser Geol. Mag. 129Ž. 3 , 281±291. EventB. Geol. Rundsch. 80, 49±72. Claoue-Long,Â J.C., Jones, P.J., Roberts, J., 1993. The age of the Bultynck, P., Martin, F., 1995. Assessment of an old stratotype: Devonian±Carboniferous Boundary. Ann. Soc. Geol. Belg. the FrasnianrFamennian boundary at Senzeilles, Southern 115Ž. 2 , 531±549. Belgium. Bull. Inst. R. Sci. Nat. Belg., Sci. Terre 65, 5±34. Cockell, C.S., 1999. Crises and extinction in the fossil record Ð a Byvsheva, T.V., Higgs, K., Streel, M., 1984. Spore correlation role for ultraviolet radiation? Paleobiology 25Ž. 2 , 212±225. between the Rhenish Slate Mountains and the Russian Plat- Conant, L.C., Swanson, V.E., 1961. Chattanooga Shale and re- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 167

lated rocks of central Tennessee and nearby areas. Geol. Surv. Daurer, A.Ž. Eds. , North Gondwana: Mid-Paleozoic Terranes, Prof. Pap.Ž. U. S. 237, 91 pp. Stratigraphy and Biota. Abh. Geol. Bundesanst.Ž. Austria vol. Copper, P., 1977. Palaeolatitudes in the Devonian of Brazil and 54, pp. 213±237. the Frasnian±Famennian mass extinction. Palaeogeogr., Dickins, J.M., 1993. Climate of the Late Devonian to Triassic. Palaeoclimatol., Palaeoecol. 21, 165±207. Palaeogeogr., Palaeoclimatol., Palaeoecol. 100, 89±94. Copper, P., 1986. Frasnian±Famennian mass extinctions and cold Dreesen, R., 1986. Event-Stratigraphy of the Belgian Famennian water oceans. Geology 14, 835±838. Ž.Uppermost Devonian, Ardennes Shelf . In: Vogel, A., Miller, Copper, P., 1998. Evaluating the Frasnian±Famennian mass ex- H., Greiling, R.Ž. Eds. , The Rhenish Massif, Structure, Evo- tinction: comparing brachiopod faunas. Acta Palaeontol. Pol. lution, Mineral Deposits and Present Geodynamics, 43Ž. 2 , 137±154. BrauschweigrWiesbaden, pp. 22±36. Coquel, R., Moreau-Benoit, A., 1986. Les spores des SeriesÂ Dreesen, R., Poty, E., Streel, M., Thorez, J., 1993. Late Famen- struniennes et tournaisiennes de Libye occidentale. Rev. Mi- nian to Namurian in the eastern Ardenne, Belgium, I.U.G.S., cropaleontol. 29, 17±43. Subcom. Carb. Strat. Guidebook. LiegeÁÁ University, Liege, 60 Cowie, J.W., Ziegler, W., Remane, J., 1989. Stratigraphic Com- pp. mission accelerates progress, 1984±1989. Episodes 12, 79±83. Fairon-Demaret, M., 1986. Some uppermost Devonian megaflo- Cressler, W.L., Daeschler, E.B., 1999. Site analysis of an Ar- ras: a stratigraphical review. Ann. Soc. Geol. Belg. 109, chaeopteris-dominated community, Red Hill, Pennsylvania. 43±48. XVI Int. Bot. Congr., St. Louis, USA. 14, Abstracts. Fairon-Demaret, M., Scheckler, S.E., 1987. Typification and re- Crowell, J.C., 1999. Pre-Mesozoic Ice Ages: their bearing on description of Moresnetia zalesskyi Stockmans, 1948, an early understanding the climate system. Geol. Soc. Am. Mem. 192, seed plant from the Upper Famennian of Belgium. Bull. Inst. 106 pp. R. Sci. Nat. Belg., Sci. Terre 57, 183±199. Crowell, J.C., Frakes, L.A., 1970. Phanerozoic glaciation and the Fisher, A.G., Arthur, M.A., 1977. Secular variations in the pelagic causes of ice ages. Am. J. Sci. 268, 193±224. realm. Spec. Publ.-Soc. Econ. Paleontol. Mineral. 25, 19±50. Crowell, J.C., Frakes, L.A., 1972. Late Paleozoic glaciation: Part Fordham, B.G., 1992. Chronometric calibration of mid-Ordovi- V. Karroo Basin, South Africa. Geol. Soc. Am. Bull. 83, cian to Tournaisian conodont zones: a compilation from recent 2887±2912. graphic-correlation and isotope studies. Geol. Mag. 129, 709± Crowley, T.J., North, G.R., 1988. Abrupt climate change and 721. extinction events in Earth history. Science 240, 996±1002. Frakes, L.A., Francis, J.E., Syktus, J.I., 1992. Climate Modes of Daemon, R.F., 1974. Palinomorfos-guias do Devoniano Superior e the Phanerozoic. Cambridge Univ. Press, Cambridge, 274 pp. CarbonõferoÂÂ Inferior das Bacias do Amazonas e Parnaõba. Geldsetzer, H.H.J., Goodfellow, W.D., McLaren, D.J., Orchard, Ann. Acad. Bras. Cienc. 46Ž. 3±4 , 549±587. M.J., 1985. The Frasnian-Famennian boundary near Jasper, Daemon, R.F., 1976. CorrelacËaoÄÂ bioestratigrafica entre os sedi- Alberta, Canada. Geol. Soc. Am.Ž. Abstract with programs 17, mentos do Siluriano, Devoniano e CarbonõferoÂ Inferior das 589. bacias do Amazonas, ParnaõbaÂÂ e Parana. 29th Congr. Bras. Girard, C., 1994. Conodont Biofacies and Event stratigraphy Geol., Ouro Preto, Anais, vol. 2, pp. 189±194. across the DrC Boundary in the stratotype areaŽ Montagne Daemon, R.F., Contreiras, C.J.A., 1971. Zoneamento palinologicoÂ Noire, France. . CFS, Cour. Forschungsinst. Senckenberg 168, da Bacia do Amazonas. 25th Congr. Bras. Geol., SaoÄ Paulo, 299±309. Anais, vol. 3, pp. 79±88. Girard, C., 1995. Les biofacies aÁÁ conodontes a la limite Dennison, J.M., Boucot, A.J., 1974. Little War Gap at Clinch FrasnienrFamennien en Montagne NoireŽ. France . Implica- Mountain provides standard reference section for Silurian tions stratigraphiques. C. R. Acad. Sci. Paris 321Ž. IIa , 689± Clinch Mountain Sandstone and most nearly complete Devo- 692. nian section in eastern Tennessee. Southeast Geol. 16, 79±101. Gradstein, F.M., Ogg, J., 1996. A Phanerozoic timescale. Episodes Devleeschouwer, X., 1999. La transition Frasnien-Famennien 19, 3±5. Ž.DevonienÂÂ Superieur en Europe: sedimentologie, Â stratigraphie Grenfell, H.R., 1995. Probable fossil zygnematacean algal spore sequentielleÂÂÂÁ et susceptibilite magnetique. These doctorat Univ. genera. Rev. Palaeobot. Palynol. 84, 201±220. libre de Bruxelles et UniversiteÂ Sc. et Techn. Lille, 412 pp. Hallam, A., 1992. Phanerozoic Sea-level Changes. Columbia Uni- Diaz, E., Isaacson, P.E., Lema, J.C., Christensen, K.L., Vavrdova, versity Press, New York. .M., Antelo, B., 1993a. Significance of a late Devonian Hallam, A., Wignall, P.B., 1997. Mass Extinctions and their Ž.Famennian glacial marine diamictite, Northern Altiplano, Aftermath. Oxford University Press, Oxford, 320 pp. Bolivia. C. R. XII ICCP, Buenos-Aires, vol. 1, pp. 293±304. Hallam, A., Wignall, P.B., 1999. Mass extinctions and sea-level Diaz, E., Palmer, B.A., Lema, J.C., 1993b. The Carboniferous changes. Earth Sci. Rev. 48, 217±250. sequence of the Northern Altiplano of Bolivia: from glacial- Heckel, P.H., Witzke, B.J., 1979. Devonian world palaeogeogra- marine to carbonate deposition. C. R. XII ICCP, Buenos-Aires, phy determined from distribution of carbonates and related vol. 2, pp. 203±222. lithic palaeoclimatic indicators. In: House, M.R., Scrutton, Diaz, E., Vavrdova, M., Bek, J., Isaacson, P.E., 1999. Late C.T., Bassett, M.G.Ž. Eds. , The Devonian System. Spec. Pap. DevonianŽ. Famennian Glaciation in Western Gondwana: evi- Palaeontol., vol. 23, pp. 99±123. dence from the Central Andes. In: Feist, R., Talent, J.A., Herbosch, A., Claeys, P., Kyte, F., 1996. Etude geochimiqueÂ de la 168 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

limite Frasnien-Famennien aÁ HonyŽ. Belgique . 17th IAS Re- eustatic cycles around margin of Old Red Continent. Ann. gional African-European Meeting of Sedimentology, Spox Soc. Geol. Belg. 109, 141±147. Ž.Tunisie . 76, Abstract. Jones, T.P., 1999. The role of wildfire in carbon cycling through Herbosch, A., Claeys, P., Kyte, F., 1997a. Anoxic event geochem- the Phanerozoic. XVI Int. Bot. Congr., St. Louis, USA. 161, istry at Frasnian±Famennian Boundary in Belgium. Erlanger Abstracts. Geol. Abh. 122, 27,Ž. Abstracts . Kalvoda, J., 1986. Upper Frasnian and lower Tournaisian events Herbosch, A., Preat,ÂÂ A., Devleeschouwer, X., 1997b. Geochimie and evolution of calcareous foraminifera Ð close links to et sedimentologieÂ de la limite Frasnien±Famennien dans le climatic changes. In: Wallister, O.Ž. Ed. , Global Bio-Events. stratotype de CoumiacŽ. Montagne Noire, France . 6emeÁ con- Lect. Notes Earth Sci., vol. 8. Springer, Berlin, pp. 225±236. gresÁ de l'A.S.F. Montpellier. 87, Abstract. Kammer, T.W., 1986. Ecologic stability of the dysaerobic biofa- Higgs, K., Streel, M., 1994. Palynological age for the lower part cies during the Late Paleozoic. Lethaia 19, 109±121. of the Hangenberg Shales in Sauerland, Germany. Ann. Soc. Kegel, W., 1953. ContribuicËaoÄ para o estudo do Devoniano da Geol. Belg. 116Ž. 2 , 243±247. Bacia do Parnaõba.Â D.N.P.M., D.G.M., Rio de Janeiro 135, 38 Higgs, K., Clayton, G., Keegan, J.B., 1988. Stratigraphic and pp. systematic palynology of the Tournaisian rocks of Ireland. Keith, M.L., 1982. Violent volcanism, stagnant oceans and some Geol. Surv. Irel.Ž. Spec. Pap. 7, 1±93. inferences regarding petroleum, strata-bound ores and mass Higgs, K., Streel, M., Korn, D., Paproth, E., 1993. Palynological extinctions. Geochim. Cosmochim. Acta 46, 2621±2637. data from the Devonian±Carboniferous boundary beds in the Klapper, G., 1988. The Montagne Noire FrasnianŽ Upper Devo- new Stockum Trench II and the Hasselbach Borehole, North- nian. conodont successions. In: McMillan, N.J., Embry, A.F., ern Rhenish Massif, Germany. Ann. Soc. Geol. Belg. 115Ž. 2 , Glass, D.J.Ž. Eds. , Devonian of the World. Can. Soc. Petrol. 551±557. Geol. Mem. 14Ž. 3 , 449±468. Holser, W.T., 1977. Catastrophic chemical events in the history of Klapper, G., Foster, C.T., 1993. Shape analysis of Frasnian species ocean. Nature 267, 403±408. of the Late Devonian conodont Genus Palmatolepis. Pal. Soc. House, M., 1985. Correlation of mid-Palaeozoic ammonoid evolu- Mem. 32, 1±35. tionary events with global sedimentary perturbations. Nature Klapper, G., Feist, R., Becker, R.T., House, M.R., 1993. Defini- 313, 17±22. tion of the FrasnianrFamennian Stage boundary. Episodes 16 House, M., 1989. Ammonoid extinction events. Philos. Trans. R. Ž.4 , 433±441. Soc. London 325, 307±326. Knoll, A.H., 1986. Patterns of change in plant communities House, M., 1996. An Eocanites fauna from the early Carbonifer- through geological time. In: Diamond, J., Case, T.J.Ž. Eds. , ous of Chile and its palaeogeographic implications. Ann. Soc. Community Ecology. Harper and Row, New York, pp. 126± Geol. Belg. 117Ž. 1 , 95±105. 141. Isaacson, P.E., Hladil, J., Shen, J-W., Kalvoda, J., Grader, G., Lafleur, S., 1991. Contribution aÁÂÂÂ l'analyse des sequences gene- 1999. Late DevonianŽ. Famennian Glaciation in South Amer- tiques dans la partie la plus eleveeÂÂ de la Formation d'Evieux ica and Marine Offlap on other Continents. In: Feist, R., Ž.Famennien superieurÂÁ a Esneux. Mem. Â Lic. Sci. Geol. Â et min. Talent, J.A., Daurer, A.Ž. Eds. , North Gondwana: Mid-Paleo- UniversiteÂÁÁ de Liege, Liege, 104 pp. zoic Terranes, Stratigraphy and Biota. Abh. Geol. Bundesanst., Lang, J., Yahaya, M., El Hamet, M.O., Besombes, J.C., Cazoulat, vol. 54, pp. 239±257. M., 1991. DepotsÂÃ glaciaires du Carbonifere Á inferieur Â aÁ l'Ouest Jarvis, D.E., 1992. The stratigraphic palynology, palynofacies and de l'AõrÈ Ž. Niger . Geol. Runsch. 80 Ž. 3 , 611±622. sedimentology of the Devonian±Carboniferous Kiltorcan For- Loboziak, S., Streel, M., 1981. Miospores in Middle±Upper Fras- mation of Southern Ireland. Ph.D. Thesis, Cork, 467 pp. nian to Famennian sediments partly dated by conodonts Jeans, C.V., Long, D., Hall, M.A., Bland, D.J., Conford, C., 1991. Ž.Boulonnais, France . Rev. Palaeobot. Palynol. 34, 49±66. The geochemistry of the Plenus Marls at Dover, England: Loboziak, S., Streel, M., Vanguestaine, M., 1983. Miospores et Evidence for fluctuating oceanographic conditions and of acritarches de la Formation d'HydrequentŽ Frasnien superieurÂ glacial control during the development of the Cenomanian± aÁÂ Famennien inferieur, Boulonnais, France. . Ann. Soc. Geol. Turonian d13C anomaly. Geol. Mag. 128, 603±632. Belg. 106, 173±183. Jekhowsky, B., 1963. RepartitionÂ quantitative des grands groupes Loboziak, S., Streel, M., Caputo, M.V., Melo, J.H.G., 1992. de AmicroorganontesB Ž.spores, Hystrichospheres,Á etc. dans les Middle Devonian to Lower Carboniferous miospore stratigra- sedimentsÂÂ marins du plateau continental. C. R. Soc. Biogeogr. phy in the central ParnaõbaÂ BasinŽ. Brazil . Ann. Soc. Geol. 349, 29±47. Belg. 115, 215±226. Joachimski, M.M., Buggisch, W., 1993. Anoxic events in the late Loboziak, S., Streel, M., Caputo, M.V., Melo, J.H.G., 1993. Frasnian Ð causes of the Frasnian±Famennian faunal crisis? Middle Devonian to Lower Carboniferous miospores from Geology 21, 675±678. selected boreholes in Amazonas and ParnaõbaÂ BasinsŽ. Brazil : Johnson, J.G., Klapper, G., Sandberg, C.A., 1985. Devonian additional data, synthesis, and correlation. Doc. Lab. Geol. eustatic fluctuations in Euramerica. Geol. Soc. Am. Bull. 96, Fac. Sci. Lyon 125, 277±289. 567±587. Loboziak, S., Melo, J.H.G., Rodrigues, R., Streel, M., Quadros, Johnson, J.G., Klapper, G., Sandberg, C.A., 1986. Late Devonian L.P., Barrilari, I.M.R., 1996. Age and correlation of the M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 169

Barreirinha FormationŽ. Curua Group, Amazon Basin : new 1960.Ž Chitinozoa . in the Devonian of Brazil and its biostrati- evidence from the miospore biostratigraphy. Acad. Bras. Cienc. graphic significance. Simp. Sul-Am. Siluro-Devon., Ponta 68Ž. 2 , 207±212. Grossa, Anais. pp. 263±281. Loboziak, S., Melo, J.H.G., Matsuda, N.S., Quadros, L.P., 1997a. Melo, J.H.G., Loboziak, S., Streel, M., 1999. Latest Devonian to Miospore biostratigraphy of the type Barreirinha Formation early Late Carboniferous biostratigraphy of northern Brazil: an Ž.Curua Group, Upper Devonian in the TapajosÂ River area, update. Bull.-Cent. Rech. Explor.-Prod. Elf-Aquitaine 22Ž. 1 , Amazon Basin, North Brazil. Bull.-Cent. Rech. Explor.-Prod. 13±33. Elf-Aquitaine 21Ž. 1 , 187±205. Meyerhoff, A.A., Boucot, A.J., Meyerhoff-Hull, D., Dickins, J.M., Loboziak, S., Melo, J.H.G., Quadros, L.P., Streel, M., 1997b. 1996. Phanerozoic faunal and floral realms of the Earth: the Palynological evaluation of the Famennian Protosalvinia intercalary relations of the Malvinokaffric and Gondwana Ž.Foerstia Zone in the Amazon Basin, northern Brazil: a faunal realms with the Tethyan faunal realm. Geol. Soc. Am. preliminary study. Rev. Palaeobot. Palynol. 9, 31±45. Mem. 189, 1±69. Malzahn, E., 1957. Devonisches glazial in PiauiŽ. Brasilien , ein Miller, K.G., Barrera, E., Olsson, R.K., Sugerman, P.J., Savin, neuer Beitrag zur Eiszeit des Devon. Geol. Jahrb. Beih. 25, S.M., 1999. Does ice drive early Maastrichtian eustasy? Geol- 1±31. ogy 27Ž. 9 , 783±786. Marini, F., Casier, J.-G., 1997. Glass beads from reflective road Muchez, P., Boulvain, F., Dreesen, R., Hou, H.F., 1996. Sequence markings: potential contaminants versus microtektites? First stratigraphy of the Frasnian±Famennian transitional strata: a evaluation. In: Raukas, A.Ž. Ed. , Impact and Extraterrestrial comparison between South China and southern Belgium. Spherules: New Tools for Global Correlation. Int. Symp. Palaeogeogr., Palaeoclimatol., Palaeoecol. 123, 289±296. Tallinn, July 1±5, pp. 31±32. Narkiewicz, M., Hoffman, A., 1989. The FrasnianrFamennian Marshall, J.E.A., 1996. Chapter 29A. Vegetational history of transition: the sequence of events in southern Poland and its Devonian spores. In: Jansonius, J., McGregor, D.C.Ž. Eds. , implications. Acta Geol. Pol. 39, 1±4. Palynology: Principles and Applications. A.A.S.P. Found., Naumova, S.N., 1953. Spore-pollen assemblages of the Upper vol. 3, pp. 1133±1141. Devonian of the Russian Platform and their stratigraphic sig- Marshall, J.E.A., Astin, T.R., Clack, J.A., 1999. East Greenland nificance. Trans. Inst. Geol. Sci. Acad. Sci. USSR 143, 204 tetrapods are Devonian in age. Geology 27Ž. 7 , 637±640. pp.Ž. in Russian . Martin, F., 1985. Acritarches du Frasnien SuperieurÂ et du Famen- Norris, R.D., Rohl,È U., 1999. Carbon cycling and chronology of nien InferieurÂÂ du bord meridional du Bassin de DinantŽ Arde- climate warming during the PalaeocenerEocene transition. nne belge.Ž. . Bull. Inst. R. Sci. Nat. Belg. 55 7 , 1±57. Nature 401, 775±778. Martin, F., 1993. Acritarchs: a review. Biol. Rev. 68, 475±538. Obukhovskaya, T.G., Avkhimovitch, V.I., Streel, M., Loboziak, Maziane, N., 1997. Evidence of Brazilian miospore zones in the S., in press. Miospores from the Frasnian±Famennian Bound- uppermost Devonian in Ghana. Int. Ass. African Palynology, ary deposits in Eastern EuropeŽ the Pripyat Depression, Be- 3rd Symposium, Johannesburg. 27, Abstract. larus and the Timan Pechora Province, Russia. and compari- Maziane, N., Higgs, K.T., Streel, M., 1999. Revision of the late son with Western EuropeŽ. Northern France . Rev. Palaeobot. Famennian miospore zonation scheme in eastern Belgium. J. Palynol. Micropalaeontol. 18, 17±25. Olempska, E., 1997. Changes in benthic ostracod assemblages McGhee, G.R., 1996. The Late Devonian mass extinction Ð the across the Devonian±Carboniferous boundary in the Holy FrasnianrFamennian crisis. Critical Moments in Paleobiology Cross Mountains, Poland. Acta Palaeontol. Pol. 42Ž. 2 , 291± and Earth History Series. Columbia University Press, New 332. York, 303 pp. Ormiston, A.R., Klapper, G., 1992. Paleoclimate, controls on McGregor, D.C., 1969. Devonian plant fossils of the genera Upper Devonian source rock sequences and stacked extinc- KryshtofoÕichia, Nikitinsporites, and Archaeoperisaccus. tions. Fifth North Am. Pal. Conv., Pal. Soc. Spec. Publ. 6, Geol. Surv. Can. Bull. 182, 91±106. 227, Abstracts and program. McGregor, D.C., 1979. Spores in Devonian stratigraphical correla- Ormiston, A.R., Oglesby, R.J., 1995. Chapter 5. Effect of Late tion. In: House, M.R., Scrutton, C.T., Bassett, M.G.Ž. Eds. , Devonian Paleoclimate on Source Rock Quality and Location. The Devonian System. Spec. Pap. Palaeontol., vol. 23, pp. In: Huc, A.-Y.Ž. Ed. , Paleogeography, Paleoclimate, and 163±184. Source Rocks. AAPG Stud. Geol., vol. 40, pp. 105±132. McGregor, D.C., McCutcheon, S.R., 1988. Implications of spore Over, D.J., 1997. Conodont biostratigraphy of the Java Formation evidence for Late Devonian age of the Piskahegan Group, Ž.Upper Devonian and the Frasnian±Famennian boundary in southwestern New Brunswick. Can. J. Earth Sci. 25, 1349± western New York State. Spec. Pap.-Geol. Soc. Am. 321, 1364. 161±177. McLaren, D.J., 1970. Time, life, and boundaries. J. Paleontol. 44, Paproth, E., Streel, M., 1985. In search of a Devonian±Carbonif- 801±815. erous Boundary. Episodes 8Ž. 2 , 110±111. McLaren, D.J., 1988. Detection and significance of mass killings. Paproth, E., Feist, R., Flajs, G., 1991. Decision on the Devonian± In: McMillan, N.J., Embry, A.F., Glass, D.J.Ž. Eds. , Devonian Carboniferous boundary stratotype. Episodes 14, 331±336. of the World. Can. Soc. Petrol. Geol. Mem. 14Ž. 3 , 1±7. Paris, F., Nolvak, J., 1999. Biological interpretation and paleobio- Melo, J.H.G., Grahn, Y., Loboziak, S., Paris, F., 1996. First diversity of a cryptic fossil group: the AChitinozoan animalB. record of Fungochitina fenestrataŽ Taugourdeau and Jekhowsky Geobios 32Ž. 2 , 315±324. 170 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Paris, F., Robardet, M., 1990. Early Palaeozoic palaeobiogeogra- covery of peat-forming plants. Geol. Soc. Am. Bull. 108Ž. 2 , phy of the Variscan regions. Tectonophysics 177, 193±213. 195±207. Paris, F., Richardson, F., Riegel, J.B., Streel, W., Vanguestaine, Richardson, J.B., Ahmed, S., 1988. Miospores, zonation and M., 1985. DevonianŽ. Emsian±Famennian palynomorphs. J. correlation of Upper Devonian sequences from western New Micropalaeontol. 4Ž. 1 , 49±81. York State and Pennsylvania. In: McMillan, N.J., Embry, Paris, F., Girard, C., Feist, R., Winchester-Seeto, T., 1996. Chiti- A.F., Glass, D.J.Ž. Eds. , Devonian of the World. Can. Soc. nozoan bio-event in the Frasnian±Famennian boundary beds at Petrol. Geol. Mem. 14Ž. 3 , 541±558. La SerreŽ. Montagne Noire, Southern France . Palaeogeogr., Richardson, J.B., McGregor, D.C., 1986. Silurian and Devonian Palaeoclimatol., Palaeoecol. 121, 131±145. spore zones of the Old Red Sandstone continent and adjacent Pedersen, T.F., Calvert, S.E., 1990. Anoxia vs. productivity: what regions. Geol. Surv. Can. Bull. 364, 1±79. controls the formation of organic-carbon-rich sediments and Rocha-Campos, A.C., 1981. G19, Middle±Late Devonian CabecËas sedimentary rocks? Am. Assoc. Petrol. Geol. Bull. 74Ž. 4 , Formation, ParnaõbaÂ Basin, Brazil. In: Hambrey, M.J., Har- 454±466. land, W.B.Ž. Eds. , Earth's Pre-Pleistocene Glacial Record. Perez-Leyton, M., 1991. Miospores du DevonienÂ moyen et Cambridge Univ. Press, Cambridge, pp. 892±895. superieurÂ de la coupe de Bermejo-La AngosturaŽ sud-est de la Sablock, P.E., 1993. A warm to cold paleoclimate change in Bolivie.Ž. . Ann. Soc. Geol. Belg. 113 2 , 373±389. GondwanaŽ. Devonian through Carboniferous : a consequence Peterson, J., Clarke, A., 1983. Petroleum geology and resources of of coupled continental shift and onlap. C. R. XII ICCP, the Volga-Ural Province, USSR. Geol. Surv. Circ. 885, 1±27. Buenos-Aires 1, 355±367. Playford, P.E., Hurley, N.F., Kerans, C., Middleton, M.F., 1989. Sandberg, C.A., Ziegler, W., 1996. Devonian conodont bio- Reefal platform development, Devonian of the Canning Basin, chronology in geologic time calibration. Senckenbergiana Western Australia. Controls on Carbonate Platform and Basin Lethaea 76Ž. 1±2 , 259±265. Development. Spec. Publ.-SEPMŽ. Soc. Sediment. Geol. vol. Sandberg, C.A., Ziegler, W., Dreesen, R., Butler, J.L., 1988. Late 44, pp. 187±202. frasnian mass extinction: conodont event stratigraphy, global Poty, E., 1999. Famennian and Tournaisian recoveries of shallow changes, and possible causes. CFS, Cour. Forschungsinst. water Rugosa following Late Frasnian and Late Strunian Senckenberg 102, 263±307. crisis, Southern Belgium and surrounding areas, HunanŽ South Sandberg, C.A., Morrow, J.R., Warme, J.E., 1997. Late Devonian China.Ž. and Omolon Region N-E Siberia . Palaeogeogr., Alamo Impact Event, Global Kellwasser Events, and Major Palaeoclimatol., Palaeoecol. 154Ž. 1±2 , 11±26. Eustatic Events, Eastern Great Basin, Nevada and Utah. Poumot, C., 1989. Palynological evidence for eustatic events in Brigham Young Univ. Geol. Stud. 42Ž. 1 , 160. the tropical Neogene. Bull.-Cent. Rech. Explor.-Prod. Elf- Scheckler, S.E., 1986. Geology, floristics and paleoecology of Aquitaine 13Ž. 2 , 437±453. Late Devonian coal swamps from Appalachian Laurentia Racheboeuf, P.R., Le Herisse,Â A., Paris, F., Babin, C., Guil- Ž.USA . Ann. Soc. Geol. Belg. 109, 209±222. locheau, F., Truyols-Massoni, M., Suarez-Soruco,Â R., 1993. Scheckler, S.E., Cressler, W.L., Connery, T., Kavins, S., Post- Le DevonienÂ de Bolivie: biostratigraphie et chronostratigra- nikoff, D.L., 1999. Devonian shrub and tree dominated land- phie. C. R. Acad. Sci. Paris 317Ž. II , 795±802. scapes. XVI Int. Bot. Congr., St. Louis, USA. 13, Abstracts. Racki, G., 1998a. The Frasnian±Famennian brachiopod extinction Schindler, E., 1990. Die Kellwasser-KriseŽ hohe Frasne-Stufe, events: a preliminary review. Acta Palaeontol. Pol. 43Ž. 2 , Ober-Devon. . GottingerÈÈ ArB. Geol. Palaont. 46, 115 pp. 395±411. Schindler, E., 1993. Event-stratigraphic markers within the Kell- Racki, G., 1998b. Frasnian±Famennian biotic crisis: undervalued wasser Crisis near the FrasnianrFamennian boundaryŽ Upper tectonic control? Palaeogeogr., Palaeoclimatol., Palaeoecol. Devonian. in Germany. Palaeogeogr., Palaeoclimatol., 141, 177±198. Palaeoecol. 104, 115±125. Racki, G., 1999. The Frasnian±Famennian biotic crisis: how many Schulke,È I., 1998. Conodont community structure around the Ž.if any bolide impacts? Geol. Rundsch. 87, 617±632. AKellwasser mass extinction eventB ŽFrasnianrFamennian Rampino, M.R., Haggerty, B.M., 1996. Impact crises and mass boundary interval. . Senckenbergiana Lethaea 7, 87±99. extinctions: a working hypothesis. Spec. Pap.-Geol. Soc. Am. Scotese, C.R., McKerrow, W.S., 1990. Revised world maps and 307, 11±30. introduction. In: McKerrow, W.S., Scotese, C.R.Ž. Eds. , Raymond, A., Metz, C., 1995. Laurussian land-plant diversity Palaeozoic Paleogeography and Biogeography. Geol. Soc. during the Silurian and Devonian: mass extinction, sampling Mem., vol. 12, pp. 1±21. bias or both? Paleobiology 21, 74±91. Scotese, C.R., Boucot, A.J., McKerrow, W.S., 1999. Gondwanan Raymond, A., Kelley, P.H., Lutken, C.B., 1989. Polar glaciers and palaeogeography and palaeoclimatology. J. Afr. Earth Sci. 28 life at the equator: the history of Dinantian and Namurian Ž.1 , 99±114. Ž.Carboniferous climate. Geology 17, 408±411. Sepkoski, J.J., 1982. A compendium of fossil marine families. Renaud, S., Girard, C., 1999. Strategies of survival during ex- Contrib. Biol. Geol., vol. 51. Milwaukee Museum Publica- treme environmental perturbations: evolution of conodonts in tions, 125 pp. response to the Kellwasser crisisŽ. Upper Devonian . Palaeo- Sepkoski, J.J., 1986. Phanerozoic overview of mass extinctions. geogr., Palaeoclimatol., Palaeoecol. 146, 19±32. In: Raup, D.M., Jablonski, D.Ž. Eds. , Patterns and Processes in Retallack, G.J., Veevers, J.J., Morante, R., 1996. Global coal gap the History of Life. Springer, Berlin, pp. 277±295. between Permian±Triassic extinction and Middle Triassic re- Sepkoski, J.J., 1996. Patterns of Phanerozoic extinction: a per- M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 171

spective from global data bases. In: Walliser, O.H.Ž. Ed. , siliciclastic layer near the FrasnianrFamennian boundary at Global Events and Event Stratigraphy in the Phanerozoic. two shelf facies localities in Belgium. Bull. Soc. Belg. Geol. Springer, Berlin, pp. 35±51. 98, 109±114. Simakov, K., 1993. The dynamics and biochronological structure Streel, M., Higgs, K., Loboziak, S., Riegel, W., Steemans, P., of the Hangenbergian bioevent. Palaeogeogr., Palaeoclimatol., 1987. Spore stratigraphy and correlation with faunas and floras Palaeoecol. 104, 127±137. in the type marine Devonian of the Ardenne±Rhenish regions. Sims, H., 1999. The early radiation of seed plants: evolutionary Rev. Palaeobot. Palynol. 50, 211±229. patterns of seed morphology in the Late Paleozoic. XVI Int. Streel, M., Fairon-Demaret, M., Loboziak, S., 1990. Givetian± Bot. Congr., St. Louis, USA. 40, Abstracts. Frasnian phytogeography of Euramerica and western Gond- Smith, A.G., 1997. Estimates of the Earth's spinŽ. geographic axis wana based on miospore distribution. In: McKerrow, W.S., relative to Gondwana from glacial sediments and paleomag- Scotese, C.R.Ž. Eds. , Palaeozoic Paleogeography and Biogeog- netism. Earth Sci. Rev. 42, 161±179. raphy. Geol. Soc. Mem. 12, pp. 291±296. Somers, Y., Streel, M., 1978. Spores du sommet du DevonienÂÁ a Streel, M., Brice, D., Degardin, J.-M., Derycke, C., Dreesen, R., LangenaubachŽ. synclinal de la Dill, RFA . Relations entre la Groessens, E., Hance, L., Legrand-Blain, M., Lethiers, F., conservation des spores, le pouvoir reflecteurÂ de la vitrinite et Loboziak, S., Maziane, N., Milhau, B., Mistiaen, B., Poty, E., des intrusions diabasiques. Ann. Mines Belg. 7±8, 147±154. Rohart, J.-C., Sartenaer, P., Thorez, J., Vachard, D., Blieck, Sorauf, J.E., Pedder, A.E.H., 1986. Late Devonian rugose corals A.,1999. Proposal for a Strunian Substage and a subdivision of and the Frasnian±Famennian crisis. Can. J. Earth Sci. 23, the Famennian Stage into four Substages. I.U.G.S. Subcom- 1265±1287. mission on Devonian Stratigraphy, Newsletter 15Ž December Stanley, S.M., 1984. Temperature and biotic crises in the marine 1998. , pp. 47±52. realm. Geology 12, 205±208. Streel, M., Caputo, M.V., Loboziak, S., Melo, J.H.G., Thorez, J., Steemans, P., Fang, X.S., Streel, M., 1996. Retizonomonoletes in press. Palynology and sedimentology of laminites and tillites hunanensis Fang and others, 1993 and the lepidophyta mor- from the latest Famennian of the ParnaõbaÂ Basin, Brazil. Geol. phon. Mem. Inst. Geol. Univ. Louvain 36, 7±88. Belgica. Streel, M., 1962. Les savanes boiseesÂÁ a Acacia et Combretum de Strother, P.K., 1996. Chapter 5. Acritarchs. In: Jansonius, J., la Lufira moyenne dans l'evolutionÂÂÂ de la vegetation katan- McGregor, D.C.Ž. Eds. , Palynology: Principles and Applica- gaise. Acad. R. Sci. Outre-mer Bull. 8Ž. 2 , 229±255. tions. A.A.S.P. Found., vol. 1, pp. 81±106. Streel, M., 1986. Miospore contribution to the Upper Tappan, H., 1971. Faunal extinction. McGraw-Hill Yearbook of Famennian±Strunian Event stratigraphy. Ann. Soc. Geol. Belg. Science and Technology. pp. 214±217. 109, 75±92. Tappan, H., 1982. Extinction or survival: selectivity and causes of Streel, M., 1992. Climatic impact on Famennian miospore distri- Phanerozoic crises. In: Silver, L.T., Schultz, P.H.Ž. Eds. , bution. Fifth Int. Conf. Global BioeventsŽ. IGCP 216 , Gottin-È Geological Implications of Impacts of Large Asteroids and gen, 108±109, Abstracts. Comets on the Earth. Spec. Pap.-Geol. Soc. Am., vol. 190, pp. Streel, M., 1999. Quantitative palynology of Famennian Events in 265±276. the Ardenne±Rhine Regions. In: Feist, R., Talent, J.A., Dau- Tappan, H., 1986. Phytoplankton: below the salt at the global rer, A.Ž. Eds. , North Gondwana: Mid-Paleozoic Terranes, table. J. Paleontol. 60, 544±545. Stratigraphy and Biota. Abh. Geol. Bundesanst.Ž. Austria 54, Tappan, H., Loeblich, A.R., 1972. Fluctuating rates of protistan pp. 201±212. evolution, diversification and extinction. 24th Int. Geol. Congr., Streel, M., Loboziak, S., 1994. Observations on the establishment Paleont., Sect. 7. pp. 205±213. of a Devonian and Lower Carboniferous high-resolution Tappan, H., Loeblich, A.R., 1973. Evolution of the oceanic miospore biostratigraphy. Rev. Palaeobot. Palynol. 83, 261± plankton. Earth Sci. Rev. 9, 207±240. 273. Thompson, J.B., Newton, C.R., 1988. Late Devonian mass extinc- Streel, M., Loboziak, S., 1996. Chapter 18B. Middle and Upper tion Episodic climatic cooling or warming? In: McMillan, Devonian miospores. In: Jansonius, J., McGregor, D.C.Ž. Eds. , N.J., Embry, A.F., Glass, D.J.Ž. Eds. , Devonian of the World. Palynology: Principles and Applications. A.A.S.P. Found., Can. Soc. Petrol. Geol. Mem. 14Ž. 3 , 29±34. vol. 2, pp. 575±587. Thorez, J., Dreesen, R., 1997. Sequence-andŽ. bio event stratigra- Streel, M., Scheckler, S.E., 1990. Miospore lateral distribution in phy: a tool for global correlation in Euramerica, as exempli- upper Famennian alluvial, lagoonal to tidal facies from eastern fied by the late Upper Devonian in Belgium. In: Feist, R. United States and Belgium. Rev. Palaeobot. Palynol. 64, 315± Ž.Ed. , Proc. Inaug. Meet. IGCP 421, Vienna. pp. 57±62, 324. Abstract. Streel, M., Theron, J.N., 1999. The Devonian±Carboniferous Tucker, R.D., Bradley, D.C., Ver Straeten, C.A., Harris, A.G., boundary in South Africa and the age of the earliest episode of Ebert, J.R., McCutcheon, S.R., 1998. New U±Pb zircon ages the Dwyka glaciation: new palynological result. Episodes 22 and the duration and division of Devonian time. Earth Plane- Ž.1 , 41±44. tary Sci. Lett. 158, 175±186. Streel, M., Traverse, A., 1978. Spores from the DevonianrMissis- Ulmishek, G., 1982. Petroleum geology and resource assessment sippian transition near the Horseshoe Curve section, Altoona, of the Timan-Pechora Basin, USSR, and the adjacent Barents- Pennsylvania, USA. Rev. Palaeobot. Palynol. 26, 21±39. Northern Kara shelf. Argonne National Laboratory, Energy Streel, M., Vanguestaine, M., 1989. Palynomorph distribution in a and Environmental System Division, TM, 199 pp. 172 M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173

Urbanek, A., 1993. Biotic crises in the history of Upper Silurian boniferous. In: Walliser, O.H.Ž. Ed. , Global Events and Event graptoloids: a palaeobiological model. Hist. Biol. 7, 29±50. Stratigraphy in the Phanerozoic. Springer, Berlin, pp. 225±250. Valentine, J.W., 1984. Neogene marine climate trends: implica- Walter, H., 1984. Vegetation und klimazonen Ð Grundriss der tions for biogeography and evolution of the shallow-sea biota. globalen Okologie.È Eugen Ulmer, Stuttgart, 230 pp. Geology 12, 647±650. Wang, K., Attrep, M. Jr., Orth, C.J., 1993. Global iridium anomaly, Van der Voo, R., 1988. Paleozoic paleogeography of North mass extinction, and redox change at the Devonian±Carbonif- America, Gondwana, and intervening displaced terranes: com- erous boundary. Geology 21, 1071±1074. parisons of paleomagnetism with paleoclimatology and bio- Weis, D., Herbosch, A., Preat,Â A., 1998. Geochemistry and Sr-iso- geographical patterns. Geol. Soc. Am. Bull. 100, 311±324. topic geochemistry of the FrF boundary Coumiac section Vanguestaine, M., 1986. Late Devonian and Carboniferous Ž.France : inferences for sea-level variations. Goldschmidt Acritarch stratigraphy and paleogeography. Ann. Soc. Geol. Conference 1998, Toulouse. Mineral. Mag. 62AŽ. 3 , 1645± Belg. 109, 93±102. 1646. Vanguestaine, M., Declairfayt, T., Rouhart, A., Smeesters, A., Weldon, S., 1997. A preliminary study of Late Devonian acritarchs 1983. Zonation par acritarches du Frasnien superieurÂ Ð Fa- from Riescheid, North Rheinish Slate Mountains, Germany. mennien inferieurÂ dans les bassins de Dinant, Namur, Herve et In: Fatka, O., Servais, T.Ž. Eds. , Acritarcha in Praha 1996. CampineŽ. DevonienÂÂ superieur de Belgique . Ann. Soc. Geol. Acta Univ. Carol., Geol., vol. 20, 699. Belg. 106, 121±171. Wendt, J., 1985. Disintegration of the continental margin of Van Loon, A.J., 1999. The meaning of AabruptnessB in the northwestern Gondwana: Late Devonian of the eastern Anti- geological past. Earth Sci. Rev. 45, 209±214. AtlasŽ. Morocco . Geology 13, 815±818. Van Steenwinkel, M., 1993. The Devonian±Carboniferous Bound- Wendt, J., Belka, Z., 1991. Age and Depositional Environment of ary: comparison between the Dinant Synclinorium and the Upper DevonianŽ. Early Frasnian to Early Famennian Black northern border of the Rhenish Slate Mountains; a sequence- Shales and LimestonesŽ. Kellwasser Facies in the Eastern stratigraphic view. Ann. Soc. Geol. Belg. 115Ž. 2 , 665±681. Anti-Atlas Morocco. Facies 25, 51±90. Vavrdova, M., Isaacson, P.E., 1999. Late Famennian Phytogeo- Went, F.W., 1953. The effect of temperature on plant growth. Ann graphic Provincialism: evidence for a limited separation of Rev. Plant Physiol. 4, 342±347. Gondwana and Laurentia. In: Feist, R., Talent, J.A., Daurer, Wignall, P.B., Twitchett, R.J., 1996. Oceanic anoxia and the end A.Ž. Eds. , North Gondwana: Mid-Paleozoic Terranes, Stratig- Permian mass extinction. Science 272, 1155±1158. raphy and Biota. Abh. Geol. Bundesanst.Ž. Austria vol. 54, pp. Wilde, P., Berry, W.B.N., 1984. Destabilization of the oceanic 453±463. density structure and its significance to marine AextinctionB Vavrdova,Â M., Isaacson, P.E., Martines, E.D., Bek, J., 1991. events. Palaeogeogr., Palaeoclimatol., Palaeoecol. 48, 143± Palinologia del limite Devonico±Carbonifero en torno al Lago 162. Titikaka, Bolivia: resultados preliminares. Rev. Tecn. Wilde, P., Berry, W.B.N., 1986. The role of oceanographic factors Yacimientos Petroliferos Fiscales Bol. 12, 303±315. in the generation of global bio-events. Lect. Notes Earth. Sci. Vavrdova,Â M., Isaacson, P.E., Diaz, E., Bek, J., 1993. Devonian± 8, 75±91. Carboniferous Boundary at Lake Titikaka, Bolivia: prelimi- Williams, D.F., 1988. Evidence for and against sea-level changes nary palynological results. C. R. XII ICCP, Buenos-Aires 1, from the stable isotopic record of the Cenozoic. In: Wilgus, 187±199. C.K., Hasting, B.S., Kendall, C.G.St.C., Posamentier, H.W., Vavrdova,Â M., Bek, J., Dufka, P., Isaacson, P.E., 1996. Palynol- Ross, C.A., Wagoner, J.C.Ž. Eds. , Sea-level Changes: An ogy of the DevonianŽ. Lochkovian to Tournaisian sequence, Integrated Approach. Spec. Publ.-Soc. Econ. Paleontol. Min- Madre de Dios Basin, northern Bolivia. Vestn. Cesk. Geol. eral., vol. 42, pp. 31±36. Ustavu 71Ž. 4 , 333±349. Witzke, B.J., 1990. Palaeoclimatic constraints for Palaeozoic Pale- Veevers, J.J., Powell, C.McA., 1987. Late Paleozoic glacial olatitudes of Laurentia and Euramerica. In: McKerrow, W.S., episodes in Gondwanaland reflected in transgressive-regres- Scotese, C.R.Ž. Eds. , Palaeozoic Paleogeography and Biogeog- sive depositional sequences in Euramerica. Geol. Soc. Am. raphy. Geol. Soc. Mem., vol. 12, pp. 57±73. Bull. 98, 475±487. Woodrow, D.L., Sevon, W.E., Richardson, J.B., 1990. Evidence Visser, J.N.J., 1990. The age of the late Palaeozoic glacigene of an impact-event in the Appalachian Basin near the Missis- deposits in southern Africa. S. Afr. J. Geol. 93Ž. 2 , 366±375. sippian±Devonian time boundary. Geol. Soc. Am. 22Ž. A92 , Visser, J.N.J., 1991. The paleoclimatic setting of the late Paleo- Abstracts with program. zoic marine ice sheet in the Karoo Basin of southern Africa. Woodruff, F., Savin, S.M., Douglas, R.G., 1981. Miocene stable In: Anderson, J.B., Ashley, J.M.Ž. Eds. , Glacial Marine Sedi- isotope record: a detailed deep Pacific Ocean study and its mentation; Paleoclimatic Significance: Boulder, Colorado. paleoclimatic implications. Science 212, 665±668. Spec. Pap.-Geol. Soc. Am., vol. 261, pp. 181±189. Xu, D.-Y., Yan, Z., Zhang, Q.-W., Shen, Z.-D., Sun, Y.-Y., Ye, Walliser, O.H., 1984. Pleading for a natural DrC-Boundary. CFS, L.-F., 1986. Significance of a d13C anomaly near the Devo- Cour. Forschungsinst. Senckenberg 67, 241±246. nianrCarboniferous boundary at the Muhua section, South Walliser, O.H., 1990. How to define AGlobal Bio-EventsB. Lect. China. Nature 321, 854±855. Notes Earth Sci. 30, 1±3. Zheng, Y., Hong-Fei, H., Liang-Fang, Y., 1993. Carbon and Walliser, O.H., 1995. Global events in the Devonian and Car- oxygen isotope event markers near the Frasnian±Famennian M. Streel et al.rEarth-Science ReÕiews 52() 2000 121±173 173

Stanislas Loboziak graduated as a geol- boundary, Luoxiu section, South China. Palaeogeogr., Palaeo- ogist from the Lille University, France. climatol., Palaeoecol. 104, 97±104. His Ph.D.Ž. 1969 was a contribution to Ziegler, W., Klapper, G., 1985. Stages of the Devonian System. the study of mio- and megaspores of the Episodes 8Ž. 2 , 104±109. Westphalian of northern France. Since Ziegler, W., Sandberg, C.A., 1990. The Late Devonian standard then he works at the same university as conodont zonation. CFS, Cour. Forschungsinst. Senckenberg researcher at the French National Centre 121, 1±115. of Scientific Research. His work deals Ziegler, W., Sandberg, C.A., 1994. Conodont phylogenetic-zone mainly with the palynology of Paleozoic concept. Stratigr. Newsl. 30, 105±123. dispersed miospores and its applications, Ziegler, W., Weddige, K., 1999. Zur Biologie, Taxonomie und especially in the field of biostratigraphy. Chronologie der Conodonten. Pal. Zeitschrift 73Ž. 1r2 , 1±38. He has contributed to the development Mario Vicente Caputo graduated in of reference scales for the Devonian and Carboniferous of West- Geology at the Federal University of ern Europe and to their implementation in comparative studies, Rio Grande do Sul in 1961, and in 1962 particularly with Central Europe, North Africa, Western Asia and he joined PetrobrasŽ the Brazilian state- North and South America. He is a consultant palynologist to Elf owned oil company. . He began his E.P. and Petrobras, and has participated for a few years, in an career as a field geologist working in updating of the biochronostratigraphy of the Devonian and Lower several basins of Northern Brazil, then Carboniferous of Paleozoic basins of northern Brazil. carried out technical and management Maurice Streel graduatedŽ. 1957 as a activities at the Stratigraphy and Sedi- botanist from Liege University, Bel- mentology Lab and the Division of In- Á gium. His Ph.D.Ž. 1961 was a contribu- terpretation of Petrobras' northern dis- tion to the phytogeography of Central trict in Belem.Â He obtained his Ph.D. African Savannahs. Later on he was degree in 1984 at the University of California, USA, specializing Assistant, and then Professor, at the Pa- on Stratigraphy and Paleoclimatology with studies on the Devo- leobotany Department of the same uni- nian glaciation in South America. He is a voting member of the versity, teaching Paleobotany and International Subcommission on the Silurian System, and the only Stratigraphy to students in Botany, Ge- Latin American representative in that commission. In 1992, he ology and Applied Geology. He intro- joined the Federal University of ParaÂ as a visiting professor, duced palynology lectures and re- lecturing on Stratigraphy, Brazilian Geology and Energy Re- searches. His main research interest was sources. Ever since he has carried out paleoclimatological research in the miospore stratigraphy of the Devonian Ardenne-Rhine in addition to teaching activities. regions. He was Secretary of the IUGS Working Group on the JoseÂ Henrique G. Melo holds a B.Sc. Devonian±Carboniferous Boundary and a voting member, and in geology from the Rio de Janeiro Fed- now corresponding member, of the International Subcommission eral UniversityŽ. 1978 , and an M.Sc. on the Devonian System. He retired from the University in 1995 from the same universityŽ. 1985 . Since but is still active as a palynologist working particularly on the 1984 he has worked at Petrobras Re- Quaternary and the quantitative approach of Late Devonian as- search CentreŽ. CENPES as a stratigra- semblages in relation to sedimentology and climatology. pher, paleontologist and palynologist. His main research interests are in Sil- urian±Devonian palynology, stratigraphy and paleogeography of Brazilian Paleozoic basins. He has also carried out palynological investigations in Ordovi- cian through Carboniferous strata of other South American countries as well as Ordovician rocks of NE Libya. Jointly with Dr. Stanislas Loboziak, he is currently leading a research project at CENPES. This involves a re-evaluation and an update of the Devonian±Mississippian miospore biostratigraphy in the Amazon and SolimoesÄ basins of northern Brazil.