The relationship between the iridium anomaly and palynological floral events at three Cretaceous-Tertiary boundary localities in western Canada

Lerbekmo, J. F.; Sweet, Arthur R.; Louis, Robert M. St.

doi:10.1130/0016-7606(1987)99<325:trbtia>2.0.co;2

Cited by 75 publications

(31 citation statements)

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“…This fern spore abundance anomaly was first reported in Orth et al (1981). Palynology has been used in high resolution investigations in non-marine mid-continental North American sections, to provide a picture of the response of the terrestrial plants to the K/T event (Tschudy et al 1984;Jerzykiewicz & Sweet 1986;Nichols et al 1986;Wolfe & Upchurch 1986;Bohor et al 1987;Lerbekmo et al 1987;Upchurch & Wolfe 1987;Johnson et al 1989;Upchurch 1989;Sweet et al 1990Sweet et al , 1999Wolfe 1991;Sweet & Braman 1992, 2001Nichols et al 1992;Braman et al 1993). The results all agree that plant communities of North America were affected simultaneously at the K/T boundary.…”

Section: North Americamentioning

confidence: 93%

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

Vajda

Raine

2003

New Zealand Journal of Geology and Geophysics

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Terrestrial pollen and spores in late Maastrichtian to early Paleocene marine strata at mid-Waipara, New Zealand, permit reconstruction of contemporary vegetation and paleoclimates. During the latest Cretaceous, spore-pollen assemblages reflect a temperate rainforest with a prominent podocarp and tree ferns component, angiosperm pollen being mainly represented by Nothofagus and Proteaceae. Disruption of the vegetation at the Cretaceous/Tertiary (K/T) boundary is recorded by an increase in fern spores, reduction in gymnosperm pollen, and temporary loss of angiosperm pollen both in mid Waipara and in the terrestrial sections of Moody Creek Mine and Compressor Creek. Following an interval of fern dominance, gymnosperms and later angiosperms return to the palynological record. The floral turnover at the K/T boundary is comparable to palynological records from North America and Japan, indicating that disruption of vegetation was global. Fern dominance is estimated to have lasted several thousands of years, based on foraminiferal biostratigraphy of immediate post-K/T boundary strata. This is orders of magnitude greater than seen in normal seral successions following deforestation. We suggest that the observed vegetation succession is due to a prolonged period of low ambient light levels, sufficient for photosynthesis but favouring plants already adapted to these levels (such as forest ground stratum), accompanied by a moderate temperature and moisture regime.

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Section: North Americamentioning

confidence: 93%

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

Vajda

Raine

2003

New Zealand Journal of Geology and Geophysics

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“…several thousand years after) the Ir peak, and again a closer association between angiosperm pollen and the boundary. This offset between the impact layer and a rise in fern spore abundance seems to be a general characteristic of K/T boundary sections in western Canada (Lerbekmo et al, 1987). However Johnson and Hickey (1988) find no evidence for a K/T fern spike in the Williston, Powder River, and Bighorn Basins.…”

Section: Discussionmentioning

confidence: 77%

“…Unfortunately, many of the K/T boundary sites in the western interior do not allow a direct test of the synchronicity between termination of the dinosaurs and the impact layer. Only in Wyoming and Canada, where dinosaur bones have been found 1 to 4 m below the impact layer (Bohor et al, 1987b;Lerbekmo et al, 1987), and 'unreworked' dinosaur teeth 1.3 m above the Ir anomaly (Sloan et al, 1986) can evidence for and against synchronicity be cited. Outside of North America, evidence for synchronous extinctions of the dinosaurs seems to be lacking (references cited in Sloan et aI., 1986).…”

Section: Discussionmentioning

confidence: 99%

“…Both the temporary increase in ferns and the longer term trend towards pine species are taken as evidence of reforestation following devestation synchronous with the planktonic boundary, although no Ir anomaly, microspherule, or shocked quartz layer is described here. A similar shift toward gymnospore dominance above the K/T boundary, which often is characteristic of higher latitude sites in North America (e.g., Lerbekmo et al, 1987), has generally been interpretted as evidence for a gradual, moderate deterioration of climate (e.g. Hickey, 1984).…”

Section: Synchronicity Of the K/t Boundary Claysmentioning

confidence: 99%

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A critical review of the case for, and against, extraterrestrial impact at the K/T boundary

Cisowski

1990

Surv Geophys

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The discovery of an excess of Ir and other noble metals in approximately chondritic proportions at numerous sites, synchronous with the Cretaceous/Tertiary (K/T) boundary, provided hard evidence for earlier suggestions that extraterrestrial events may have coincided with many global geologic boundaries. Further support for the impact hypothesis arose from the identification of abundant microspherules and shocked quartz in K/T boundary marine and nonmarine deposits, respectively, and the discovery of an apparent periodicity in the megaextinction event record. However continuing doubts about the impact origin of the K/T spherical forms and associated geochemical anomalies, uncertainty about the range and extent of the shocked quartz distribution, and the lack of a large, suitably-aged crater, has led to an alternative hypothesis calling upon purely endogenic processes to account for the boundary layer phenomena. Advocates of this opposing theory generally call upon large scale, possibly periodic injection of mantle material directly into the lithosphere. While a number of arguments can be made from the existing data base for and against both competing theories, other evidence suggests that additional phenomena, including sudden changes in the physical and chemical conditions of the oceans, natural combustion on a global scale, and/or widespread sediment-contaminated volcanism, may have contributed to the dramatic transition recorded in the K/T boundary rock record.

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“…Bourgeouis et al (1988), Albertão et al (1992Albertão et al ( ,1994 e Albertão & Martins Jr.(1996), descreveram registros de tsunamis de grande porte, com cerca de 50-100 metros de altura. Lerbekmo & Saint Louis (1986)e Lerbekmo et al (1987) descreveram altos teores de iridium em litossomas associados à fronteira K/T e Albertão et al (1994) no Brasil e Pitakpaivan et al (1994) nos EUA mostraram minerais deformados por impacto de corpos extraterrestres ao longo da fronteira K/T. Feições similares foram descritas no Domo de Araguainha -uma estrutura circular com cerca de 40 Km de diâmetro, impressa sobre sedimentos paleozóicos da Bacia do Paraná, nos limites entre os estados de Mato Grosso e Goiás -considerada como sendo formada por um impacto de meteorito durante o Cretáceo (Dietz et al 1973, Theilen-Willige 1981, Crósta et al 1981.…”

Section: Considerações Acerca Da Evolução Climáticaunclassified

Evolução Climática Do Gondwana Na Região Centro-Sul Do Brasil E Seus Registros Geológicos Continentais Durante O Mesozóico, Enfatizando O Arco Do Paranaíba, a Borda Nne Da Bacia Do Paraná E a Porção Meridional Da Bacia Sanfrasciscana, No Oeste Do Estado D

Sgarbi¹,

Dardenne

1996

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Current theories suggest the the main cause of the temperature changes in Earth surface along the geological time, seems to be, as a concensus, the anomalous concentration of CO 2 , CH 4 and other gases in the terrestrial atmosphere. There are however divergences about the origin of these gases which are the main responsables for the greenhouse effect.This study discusses questions about the global climate changes in the geological past, commenting the mass-extinction periods of the Permian-Triassic (P/Tr) and Cretaceous/Tertiary (C/T) boundaries. The relationship between unusual high CO 2 levels in the atmosphere and mass-extinction events is commented. The origin of the greenhouse gases are attributed to: a) extensive outgassing of volatiles through of large volcanic events, or b) asteroid or cometary impact by bodies ranging up to 10 Km in diameters, or c) marine and terrestrial organic production by living organisms.Climatic changes have been detected in all the geological records, from Precambrian to Cenozoic. Tillites and varvites in Gondwana are features of Proterozoic and Paleozoic ice ages. The Mesozoic, on the other hand, had a global warm climate, exhibiting generally high level sea and low thermal variation between the poles and the equator. The Mesozoic continental geologic records in Gondwana are consequence of this arid climate, and the sedimentary rocks are mainly red-beds seguences or other related with arid/ semi-arid environments.The relationship between the climate, geological records and paleogeographical aspects in the Mesozoic Central-South Gondwana are presented, focussing the NNE border of the Paraná and the Southern Sanfranciscana basins, which occur in the western part of Minas Gerais state. The Parecis Basin that occurs in Mato Grosso State is also mentioned.These basins show sequences of varied rock types -volcanic and sedimentary ones -, and exhibit ages ranging from early to late Cretaceous.Other important paleogeographic feature studied occurs as a strip of intensely deformed Precambrian rocks forming a NW-SE tectonic arch, preserved as a succession of thrust slices. This is known as Alto do Paranaíba Arch or Alto do Paranaíba Anteclesis, (Ladeira et al. 1971, Grossi Sad et al 1971, a regional structure related with the emplacement of the Cretaceous Paraná and Sanfranciscana basins. O Mesozóico, tema do presente trabalho, também deixou profundas impressões no Brasil. Como um todo, pode ser caracterizado por uma época de clima predominantemente quente, com níveis marinhos altos e pouca variação térmica entre o equador e os polos, se comparado com as condições atuais. O registro geológico continental observado em parte do Brasil corrobora esta suposição climática, apesar das dificuldades inerentes ao estudo destas rochas, ao contrário daquelas crono-correlatas presentes em nossas bacias costeiras. As dificuldades devem-se, dentre outros fatores, à restrita importância econômica destas rochas, ao seu registro fragmentário, ao geralmente alto grau de alteração intempérica além...

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The relationship between the iridium anomaly and palynological floral events at three Cretaceous-Tertiary boundary localities in western Canada

Cited by 75 publications

References 0 publications

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid‐Waipara River, North Canterbury, New Zealand

A critical review of the case for, and against, extraterrestrial impact at the K/T boundary

Evolução Climática Do Gondwana Na Região Centro-Sul Do Brasil E Seus Registros Geológicos Continentais Durante O Mesozóico, Enfatizando O Arco Do Paranaíba, a Borda Nne Da Bacia Do Paraná E a Porção Meridional Da Bacia Sanfrasciscana, No Oeste Do Estado D

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