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Cretaceous–Paleogene boundary events
Available online at www.sciencedirect.com
Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 1 – 3 www.elsevier.com/locate/palaeo
Preface
Cretaceous–Paleogene boundary events The Cretaceous–Paleogene (K–Pg) boundary is recognized as one of the major catastrophic perturbations which affected the marine and terrestrial ecosystems and changed the earth's history and the path of evolution forever. Following this, the story of the K–Pg boundary has fascinated everyone interested in the history of life and death on our planet. In the quarter century since the publication of the seminal Alvarez et al. paper in Science in 1980, a large number of studies of the Cretaceous–Paleogene (K–Pg) boundary have been published. These papers typically have been interdisciplinary, and have involved collaborations of specialists in quite varied areas. The two topical sessions “Mass extinctions and other large ecosystem perturbations: extraterrestrial and terrestrial causes” and “K/T boundary events” at the 32nd International Geological Congress held in Florence in August 2004 that focused on mass extinctions and environmental perturbations, and on the K–Pg boundary itself, provide an opportunity to bring together some of the newest results pertaining to the K–Pg mass extinction and its causes. This special issue includes the most relevant contributions and allows these new results to be presented in the context of the history of the link between K and Pg boundary events and an extraterrestrial impact, and the possible ramifications of the impact hypothesis for the study of mass extinctions and the subdivisions of geologic time in general. In the first paper of this issue, Kring provides a description of the Chicxulub impact event and its expected environmental consequences. The environmental effects of this extraordinary event were global in their extent, largely because of the interaction of ejected debris with the atmosphere. The environmental consequences of the Chicxulub impact event and their associations with the K–Pg boundary mass extinction event, clearly indicate that impact cratering processes can affect both the geologic and biologic evolution of our planet. 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2007.02.036
Nichols presents the results of a study on the plant communities from terrestrial rocks at eight localities of western North America that preserve evidence of the Chicxulub impact. The plant microfossil record reveals a major disruption and permanent alteration at the K–Pg boundary that were a consequence of the boundary event. In particular, abrupt disappearance of pollen species (that is plant extinctions) is closely associated with impact ejecta deposits containing iridium and shocked quartz. Moreover, a fern-spore spike occurring above the K–Pg boundary at most sites is the record of pioneer plant communities on a devastated landscape. Oms and others provide new insights on the continental K–Pg transition in SW Europe through an integrated sedimentological, magnetostratigraphic, and paleontological study of a thick and continuous stratigraphic section in southeastern Pyrenees (Spain) that records deposition during the Maastrichtian and into the Paleogene. A robust magnetostratigraphy is correlated to the standard polarity scale in light of known biochronological constraints (charophyte, marine invertebrates, eggshells and other dinosaur remains). Sedimentology indicates a progressive regression from marine through lagoonal to entirely continental environments with a maximum palaeoenvironmental change (regressive peak) that, within the framework of a sudden palaeoenvironmental reorganization, affected the continental areas of SW Europe before the K–Pg boundary. Finally, after a period of renewed quiescence following the regression maximum, a Cenozoic flooding took place. Scholz and Hartman have investigated the highly diverse and well-preserved fauna of unionoid (freshwater) bivalves near the K–Pg boundary of the Western Interior (USA) that undergoes a significant turnover with a gradual, severe extinction followed by a very long period of recovery. A quantitative study based on multivariate morphometrics allowed to better understand the pattern and causes of the extinction. The
2
Preface
decrease in taxonomic diversity of unionoids in the interval spanning the K–Pg boundary is associated with a significant shift in morphospace occupation that indicates a major decrease in habitat stability. Four events and processes are discussed as possible causes of this change in habitat stability. The findings support the idea that the Chicxulub impact was not the major agent for the unionoid turnover at the end of the Cretaceous, but tectonic and eustatic processes are much more important. The authors underline conspicuous similarities of the causes for the K–Pg extinction and the modern extinction or extirpation of unionoid bivalves in the world. This may also happen today if modern environmental protection and river management programs are not put efficiently into action. The papers by Ogorelec and others and Tewari and others present δ13C and δ18O measurements and results of detailed paleontological (rudists, foraminifera, algae, gastropods, and ostracods) and paleoenvironmental analyses from shallow marine carbonate successions of the NW Adriatic Platform. They show that the recognized extreme depletion in the δ13C record at the K–Pg boundary may be related to global climate change but also to local environmental changes. The global, prominent abundance spike of the dinoflagellate Manumiella seelandica that occurred at the end of the Maastrichtian is the subject of the study by Habib and Saeedi. The authors advance the hypothesis that the coiling event recognized at the end of the Cretaceous played an important role in producing this peak abundance during an episode of marine regression. Fornaciari and co-authors report the results of an integrated micropaleontological (planktonic foraminifera and calcareous nannofossils), mineralogical and stable isotope investigation carried out in a previously undescribed lower bathyal section cropping out in Southern Alps where a complete K–Pg transition with an expanded basal Danian is preserved. The authors give evidence of a decoupling in the recovery of the coccolithophore and planktonic foraminiferal communities, the latter recovering well long before. In addition, it appears that in the initial Danian the calcareous dinoflagellates took over the ecospace occupied by coccolithophores in the terminal Maastrichtian and remained a significant component of the assemblage for about 200 kyr. The entire early Danian interval considered is characterized by low Sr/Ca ratio of the biogenic carbonates that would suggest dramatically low coccolithophore productivity. The authors speculate that the altered ecological structure of phytoplankton community and the low productivity of coccolithophores severely affected the efficiency of the transfer of
organic carbon from the photic zone to the deep ocean, thus supporting the early Danian “living ocean” model. Bernaola and Monechi provide a high-resolution calcareous nannofossil quantitative analysis across the K–Pg boundary at ODP Site 1262 on Walvis Ridge (eastern South Atlantic Ocean, paleodepth ∼2500– 3000 m). They document in detail the calcareous nannoplankton turnover across the boundary that is marked by an important decrease in calcareous nannofossil absolute abundance, the increase of Cretaceous-persistent species together with dinoflagellate cysts and the appearance of new-Paleocene taxa. A pulse of surface water cooling occurs in the uppermost Maastrichtian and the southern high latitude influx continues or even increases during the early Danian. The total recovery of the calcareous nannoplankton communities took place only some hundred thousands of years after the K–Pg boundary. Coccioni and Marsili, and Alegret have investigated the benthic foraminiferal assemblages across the K–Pg boundary respectively from the outer neritic–uppermost bathyal Elles section (NW Tunisia) and the middle bathyal Loya section (Basque–Cantabrian Basin, SW France). These studies provide evidence of a dramatic faunal and paleoenvironmental turnover in coincidence with the K–Pg boundary without significant extinction at the end of the Cretaceous. A stepped pattern of faunal recovery and restructuring is recognizable during the lowermost Danian reflecting the gradual restabilization of the environmental conditions after the K–Pg boundary event. As shown by Coccioni and Marsili, environmental instability occurred in the lowermost Danian over a period of about 25 kyr that is related to a rapidly changing of food supply driven by phytoplankton blooms. Stabilization of the surface water and sea floor ecosystems may have occurred within some tens of thousands of years, which is a considerably shorter period than commonly suggested. However, as shown by Alegret, supply to the benthos recovered more than 200 kyr after the K–Pg boundary event. The drastic change of benthic foraminiferal assemblages coincident with the K–Pg boundary at Elles and the staggered reorganization during the lowermost Paleogene are largely compatible with the catastrophic effects of a huge asteroid impact on Earth at the K–Pg boundary that severely destabilized the oceanic phytoplanktonbased food web. Acknowledgements We thank the organization of the 32nd International Geological Congress, Florence 2004, for hosting the
Preface
sessions in which these papers have been presented. Finally, we wish to acknowledge the great effort spent by many colleagues who willingly reviewed manuscripts. Without their efforts, a volume of this quality would not have been possible. These colleagues include: José Antonio Arz, William A. Clemens, Lucy E. Edwards, R. Farley Fleming, Norman Frederiksen, Simone Galeotti, Silvia Gardin, János Haas, Kirk R. Johnson, Michael A. Kaminski, Antonio Longinelli, Valeria Luciani, Nicoletta Mancin, Kenneth G. Miller, Bojan Ogorelec, Isabella Premoli Silva, Nevio Pugliese, Robert Scholger, Jan Smit, Francois Therrien, Loïc Villier, and Katarina von Salis. Reference Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208, 1095–1108.
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Rodolfo Coccioni Istituto di Geologia e Centro di Geobiologia, Università di Urbino, Campus Scientifico, Località Crocicchia, 61029 Urbino, Italy E-mail address: [email protected]. Corresponding author. Tel.: +39 0722 304237. Simonetta Monechi Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira, 4, 50121 Firenze, Italy Michael R. Rampino Department of Biology, New York University, 100 Washington Square East, New York, NY 10003-6688, USA 14 February 2007
Palaeogeography, Palaeoclimatology, Palaeoecology 255 (2007) 1 – 3 www.elsevier.com/locate/palaeo
Preface
Cretaceous–Paleogene boundary events The Cretaceous–Paleogene (K–Pg) boundary is recognized as one of the major catastrophic perturbations which affected the marine and terrestrial ecosystems and changed the earth's history and the path of evolution forever. Following this, the story of the K–Pg boundary has fascinated everyone interested in the history of life and death on our planet. In the quarter century since the publication of the seminal Alvarez et al. paper in Science in 1980, a large number of studies of the Cretaceous–Paleogene (K–Pg) boundary have been published. These papers typically have been interdisciplinary, and have involved collaborations of specialists in quite varied areas. The two topical sessions “Mass extinctions and other large ecosystem perturbations: extraterrestrial and terrestrial causes” and “K/T boundary events” at the 32nd International Geological Congress held in Florence in August 2004 that focused on mass extinctions and environmental perturbations, and on the K–Pg boundary itself, provide an opportunity to bring together some of the newest results pertaining to the K–Pg mass extinction and its causes. This special issue includes the most relevant contributions and allows these new results to be presented in the context of the history of the link between K and Pg boundary events and an extraterrestrial impact, and the possible ramifications of the impact hypothesis for the study of mass extinctions and the subdivisions of geologic time in general. In the first paper of this issue, Kring provides a description of the Chicxulub impact event and its expected environmental consequences. The environmental effects of this extraordinary event were global in their extent, largely because of the interaction of ejected debris with the atmosphere. The environmental consequences of the Chicxulub impact event and their associations with the K–Pg boundary mass extinction event, clearly indicate that impact cratering processes can affect both the geologic and biologic evolution of our planet. 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2007.02.036
Nichols presents the results of a study on the plant communities from terrestrial rocks at eight localities of western North America that preserve evidence of the Chicxulub impact. The plant microfossil record reveals a major disruption and permanent alteration at the K–Pg boundary that were a consequence of the boundary event. In particular, abrupt disappearance of pollen species (that is plant extinctions) is closely associated with impact ejecta deposits containing iridium and shocked quartz. Moreover, a fern-spore spike occurring above the K–Pg boundary at most sites is the record of pioneer plant communities on a devastated landscape. Oms and others provide new insights on the continental K–Pg transition in SW Europe through an integrated sedimentological, magnetostratigraphic, and paleontological study of a thick and continuous stratigraphic section in southeastern Pyrenees (Spain) that records deposition during the Maastrichtian and into the Paleogene. A robust magnetostratigraphy is correlated to the standard polarity scale in light of known biochronological constraints (charophyte, marine invertebrates, eggshells and other dinosaur remains). Sedimentology indicates a progressive regression from marine through lagoonal to entirely continental environments with a maximum palaeoenvironmental change (regressive peak) that, within the framework of a sudden palaeoenvironmental reorganization, affected the continental areas of SW Europe before the K–Pg boundary. Finally, after a period of renewed quiescence following the regression maximum, a Cenozoic flooding took place. Scholz and Hartman have investigated the highly diverse and well-preserved fauna of unionoid (freshwater) bivalves near the K–Pg boundary of the Western Interior (USA) that undergoes a significant turnover with a gradual, severe extinction followed by a very long period of recovery. A quantitative study based on multivariate morphometrics allowed to better understand the pattern and causes of the extinction. The
2
Preface
decrease in taxonomic diversity of unionoids in the interval spanning the K–Pg boundary is associated with a significant shift in morphospace occupation that indicates a major decrease in habitat stability. Four events and processes are discussed as possible causes of this change in habitat stability. The findings support the idea that the Chicxulub impact was not the major agent for the unionoid turnover at the end of the Cretaceous, but tectonic and eustatic processes are much more important. The authors underline conspicuous similarities of the causes for the K–Pg extinction and the modern extinction or extirpation of unionoid bivalves in the world. This may also happen today if modern environmental protection and river management programs are not put efficiently into action. The papers by Ogorelec and others and Tewari and others present δ13C and δ18O measurements and results of detailed paleontological (rudists, foraminifera, algae, gastropods, and ostracods) and paleoenvironmental analyses from shallow marine carbonate successions of the NW Adriatic Platform. They show that the recognized extreme depletion in the δ13C record at the K–Pg boundary may be related to global climate change but also to local environmental changes. The global, prominent abundance spike of the dinoflagellate Manumiella seelandica that occurred at the end of the Maastrichtian is the subject of the study by Habib and Saeedi. The authors advance the hypothesis that the coiling event recognized at the end of the Cretaceous played an important role in producing this peak abundance during an episode of marine regression. Fornaciari and co-authors report the results of an integrated micropaleontological (planktonic foraminifera and calcareous nannofossils), mineralogical and stable isotope investigation carried out in a previously undescribed lower bathyal section cropping out in Southern Alps where a complete K–Pg transition with an expanded basal Danian is preserved. The authors give evidence of a decoupling in the recovery of the coccolithophore and planktonic foraminiferal communities, the latter recovering well long before. In addition, it appears that in the initial Danian the calcareous dinoflagellates took over the ecospace occupied by coccolithophores in the terminal Maastrichtian and remained a significant component of the assemblage for about 200 kyr. The entire early Danian interval considered is characterized by low Sr/Ca ratio of the biogenic carbonates that would suggest dramatically low coccolithophore productivity. The authors speculate that the altered ecological structure of phytoplankton community and the low productivity of coccolithophores severely affected the efficiency of the transfer of
organic carbon from the photic zone to the deep ocean, thus supporting the early Danian “living ocean” model. Bernaola and Monechi provide a high-resolution calcareous nannofossil quantitative analysis across the K–Pg boundary at ODP Site 1262 on Walvis Ridge (eastern South Atlantic Ocean, paleodepth ∼2500– 3000 m). They document in detail the calcareous nannoplankton turnover across the boundary that is marked by an important decrease in calcareous nannofossil absolute abundance, the increase of Cretaceous-persistent species together with dinoflagellate cysts and the appearance of new-Paleocene taxa. A pulse of surface water cooling occurs in the uppermost Maastrichtian and the southern high latitude influx continues or even increases during the early Danian. The total recovery of the calcareous nannoplankton communities took place only some hundred thousands of years after the K–Pg boundary. Coccioni and Marsili, and Alegret have investigated the benthic foraminiferal assemblages across the K–Pg boundary respectively from the outer neritic–uppermost bathyal Elles section (NW Tunisia) and the middle bathyal Loya section (Basque–Cantabrian Basin, SW France). These studies provide evidence of a dramatic faunal and paleoenvironmental turnover in coincidence with the K–Pg boundary without significant extinction at the end of the Cretaceous. A stepped pattern of faunal recovery and restructuring is recognizable during the lowermost Danian reflecting the gradual restabilization of the environmental conditions after the K–Pg boundary event. As shown by Coccioni and Marsili, environmental instability occurred in the lowermost Danian over a period of about 25 kyr that is related to a rapidly changing of food supply driven by phytoplankton blooms. Stabilization of the surface water and sea floor ecosystems may have occurred within some tens of thousands of years, which is a considerably shorter period than commonly suggested. However, as shown by Alegret, supply to the benthos recovered more than 200 kyr after the K–Pg boundary event. The drastic change of benthic foraminiferal assemblages coincident with the K–Pg boundary at Elles and the staggered reorganization during the lowermost Paleogene are largely compatible with the catastrophic effects of a huge asteroid impact on Earth at the K–Pg boundary that severely destabilized the oceanic phytoplanktonbased food web. Acknowledgements We thank the organization of the 32nd International Geological Congress, Florence 2004, for hosting the
Preface
sessions in which these papers have been presented. Finally, we wish to acknowledge the great effort spent by many colleagues who willingly reviewed manuscripts. Without their efforts, a volume of this quality would not have been possible. These colleagues include: José Antonio Arz, William A. Clemens, Lucy E. Edwards, R. Farley Fleming, Norman Frederiksen, Simone Galeotti, Silvia Gardin, János Haas, Kirk R. Johnson, Michael A. Kaminski, Antonio Longinelli, Valeria Luciani, Nicoletta Mancin, Kenneth G. Miller, Bojan Ogorelec, Isabella Premoli Silva, Nevio Pugliese, Robert Scholger, Jan Smit, Francois Therrien, Loïc Villier, and Katarina von Salis. Reference Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208, 1095–1108.
3
Rodolfo Coccioni Istituto di Geologia e Centro di Geobiologia, Università di Urbino, Campus Scientifico, Località Crocicchia, 61029 Urbino, Italy E-mail address: [email protected]. Corresponding author. Tel.: +39 0722 304237. Simonetta Monechi Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira, 4, 50121 Firenze, Italy Michael R. Rampino Department of Biology, New York University, 100 Washington Square East, New York, NY 10003-6688, USA 14 February 2007