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[N.MacLeod@nhm.ac.uk: Re: "No Bolides!"]



Since the following was sent in response to a message which was also
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--
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)

  Date: Thu, 4 Apr 96 04:05:08 PST
  From: N.MacLeod@nhm.ac.uk (N. MacLeod)
  To: Multiple recipients of list <paleonet@ucmp1.Berkeley.EDU>
  Subject: Re: "No Bolides!"

  Sorry Tom, but I can't let this sort of disinformation go by
  unchallenged.

  > No one is saying that the comet/meteor itself killed off the
  > dinosaurs and ~75% of thier contemporaries.
  
  Not true. That is exactly what many people are saying and have been
  saying for some time...
  
  Alvarez, L. W., Alvarez, F., Asaro, F. & Michel, H. V. 1980.
  Extraterrestrial cause for the Cretaceous-Tertiary
  extinction. Science, 208, 1095-1108.
  
  Sheehan, P. M., Fastovsky, D. E., Hoffmann, R. G., Berghaus, C. B. &
  Gabriel, D. 1991. Sudden extinction of the dinosaurs: Latest
  Cretaceous, Upper Great Plains, U.S.A. Science, 254, 835-839.
  
  [see Hulbert, S. H. & Archibald, J. D. 1995. No stastistical support
  for sudden (or gradual) extinction of dinosaurs. Geology, 23,
  881-884. in reference to the Sheehan et al. study]
  
  indeed...
  
  Raup, D. M. 1991. Extinction: Bad genes or Bad Luck. W. W. Norton
  and Co., New York.
  
  ..has even suggested that all extinctions (mass and background) may
  be caused by impacts.
  
  > There is a confirmed crater in the Yucatan that is nearly 300Km in
  > diameter.
  
  Not certain. There are onging disputes over the so-called crater's
  size...
  
  Ward, W. C., Keller, G., Stinnesbeck, W. & Adatte,
  T. 1995. Yucat=E1n subsurface stratigraphy: Implications and
  constraints for the Chicxulub impact. Geology, 23, 873-876.
  
  ..have recently argued that the structure may be as small as 100 km
  and even those who support the impact model disagree among
  themselves as to how large the stucture is.
  
  > But an ecologcal disaster that may have resulted in the collapse
  > of the food web seems to have been the trigger for the mass
  > extinctions.
  
  This sounds suspiciously like a tautology to me.

  > When the impact occured 65Ma the area was a warm , shallow
  > (<300 m) carbonate platform and tremendous volumes of CO2 were
  > released, billions of gallons of sea water vaporized, flash fires
  > ignited thousands of miles away form ballistic emplacement of
  > fallout and global ranging tsunamis than may have been as high as
  > 2Km all would have had immediate effect on the biota! Longer term
  > climatic phenomena may have ranged from a super Greenhouse , to a
  > so called "nuclear winter" scenario, acid rains, etc. Massive
  > off-the scale earthquakes would probaly continue for centuries
  > (meg-aftershocks).
  
  Most of this is assumption and a-scientific scenario construction.
  Paleontology cannot address these issues. However, we can contribute
  to the debate by taking these hypotheses (the impact scenario is
  fine as a hypothesis), suggesting biotic predictions that uniquely
  derive from those hypotheses, and testing those predictions against
  the data of the fossil record. This brings us back to Mike Resse's
  original posting. If all of these terrible things happened why are
  there not high levels of extinctions among "vulnerable" terrestrial
  invertebrates and vertebrates? There doesn't even seem to be any
  change in plant-insect associations in the US west...
  
  Labandiera, C. C. 1992. Diets, diversity, and disparity: Determining
  the effect of the terminal Cretaceous extinction on insect
  evolution. Fifth North American Paleontological Convention,
  Abstracts with Programs, Special Publication of the Paleontological
  Society, 6, 174.
  
  The fact that you avoid any specific reference to the biotic
  predictions of your favored model suggests that you aren't very
  willing to get into them.  This seems curious to me since claiming
  that "the impact caused all the extinctions...except for those that
  it didn't cause" sounds like a pretty flimsy "explanation" of a mass
  extinction event.
  
  > Ecosystems would be hard pressed to withstand this stress and it
  > would be inevitable that die offs would ensue. Along with the
  > dinosaurs, I believe it was Raup who stated that no land animal
  > over 25Kg survived the event.
  
  How many fossils representing animals over 25kg are present in the
  strata within or immediately below the impact debris layer?
  None. Can you cite a single section in which a large fossil occurs
  in this position? If so, please direct me to that literature. The
  closest uncontroversial dinosaur fragment is located 60 cm below the
  Ir horizon in Montana. Sixty centimeters represents a lot of
  time. see...
  
  Williams, M. E. 1994. Catastrophic versus noncatastrophic extinction
  of the dinosaurs: Testing, falsifiability, and the burden of
  proof. Journal of Paleontology, 68, 183-190.

  > Placental mammals were very hard hit
  
  No way to tell really!
  
  Archibald, J. D. & Clemens, W. A. 1984. Mammal evolution near the
  Cretaceous-Tertiary boundary. In: Berggren, W. A. & Vancouvering,
  J. A.  eds., Catastrophes and Earth History: The New
  Uniformitarianism. Princeton University Press, Princeton, 229-371.
  
  ..show that the (relatively small number of) mammalian extinctions
  that are recorded in Bug Creek Montana appear to be related to the
  facies shift that occurs at the same time. The facies shift does not
  appear to be impact related. See also...
  
  Archibald, J. D. & Bryant, L. J. 1990. Differential
  Cretaceous-Tertiary extinction of nonmarine vertebrates; evidence
  from northeastern Montana.  In: Sharpton, V. L. & Ward, P. D. eds.,
  Global catastrophes in Earth history: an interdisciplinary
  conference on impacts, volcanism, and mass mortality. Geological
  Society of America Special Paper 247, Boulder, 549-562.
  
  Archibald, J. D. 1993. The importance of phylogenetic analysis for
  the assessment of species turnover: a case history of Paleocene
  mammals in North America. Paleobiology, 19, 1-27.
  
  
  > , so were numerous marine ceatures, i.e.  Ammonites,
  
  Nonsense! Ammonite diversity had been declining for almost 11
  million years prior to the K-T boundary...
  
  House, M. R. 1993. Fluctuations in ammonoid evolution and possible
  environmental controls. In: House, M. R. ed., The Ammonoidea:
  environment, ecology, and evolutionary change. Systematics
  Association Special Volume, 13-34.
  
  Kennedy, W. J. 1993. Ammonite faunas of the European Maastrichtian;
  diversity and extinction. In: House, M. R. ed., The Ammonoidea:
  environment, ecology, and evolutionary change. Systematics
  Association Special Volume, 285-326.
  
  The highest ammonite fossil thus far found is still 15 cm below that
  boundary...
  
  Ward, P. D., Kennedy, W. J., MacLeod, K. G. & Mount,
  J. F. 1991. Ammonite and inoceramid bivalve extinction patterns in
  Cretaceous/Tertiary boundary sections of the Biscay region
  (southwestern France, northen Spain).  Geology, 19, 1181-1184.
  
  ..in a section that is demonstrably incomplete...
  
  MacLeod, N. & Keller, G. 1991. How complete are Cretaceous/Tertiary
  boundary sections? A chronostratigraphic estimate based on graphic
  correlation. Geological Society of America Bulletin, 103, 1439-1457.
  
  Ward, P. D. & Kennedy, W. J. 1993. Maastrichtian ammonites from the
  Biscay region (France, Spain). Paleontological Society Memoir, 34,
  1-58.

  > rudists clams,

  Forget it! No rudistids are present above the middle
  Maastrichtian...
  
  Kauffman, E. G. 1984. The fabric of Cretaceous extinctions. In:
  Berggren, W. A. & Van Couvering, J. A. eds., Catastrophes and Earth
  History: The New Uniformitarianism. Princeton University Press,
  Princeton, 151-246.
  
  Johnson, C. C. & Kauffman, E. G. 1996. Maastrichtian extinction
  patterns of Carribean province rudistids. In: MacLeod, N. & Keller,
  G. eds., The Cretaceous-Tertiary Mass Extinction: Biotic and
  Environmental Changes. W.  W. Norton & Co., New York, 231-274.
  
  ..this group doesn't even figure in the extinction controversy
  anymore.
  
  > tropical reefs corals,
  
  Rudists were the principle reef-building organisms in the upper
  Cretaceous.  I'm not completely sure on this point, but I know of no
  late Maastrichtian reefs; rudist, coral, or otherwise.

  > mosasaurs,
  
  Mosasaurs make it into the Maastrichtian, but that's about it. The
  youngest Mosasaur comes from the lower Hornerstown Fm. in New
  Jersey. which is dated as Maastrichtian, but is widely acknoledged
  to be incomplete across the K-T boundary and contains no
  impact-debris whatsoever. I'm not a specialist on this group, but I
  believe that Mosasaurs are declining in taxic richness from
  Campanian - Maastrictian. Can anyone out there offer a more precise
  summary of the Mosasaur fossil record?

  > pterosaurs
  
  No way! Pterosaurs originate in the Berriasian and rich their
  maximum diversity (10 families) in the mid-Cretaceous. Only two
  genera make it into the Maastrichtian and the deposits containing
  these fossils are not of uppermost Maastrichtrian age...
  
  Wellnhofer, P. 1991. The illustrated encyclopedia of
  Pterosaurs. Salamander Books, London.
  
  > all became extinct.
  
  Sure, they all became extinct, but their extinction had nothing to
  do with a K-T impact or at least this cannot be proved from the
  paleontological evidence.
  
  
  > Zooplankton was hard hit as well,
  
  Space prevents me from commenting on this one.
  
  > and land plants were reduced.
  
  Wrong again! Hickey shows that from a taxic point of view the K-T
  boundary didn't substantially effect angiosperms...
  
  Hickey, L. J. 1984. Changes in the agiosperm flora across the
  Cretaceous-Tertiary boundary. In: Berggren, W. A. & Vancouvering,
  J. A.  eds., Catastrophes in Earth History: The New
  Uniformitarianism. Princeton University Press, Princeton, 279-313.
  
  ..what you're probably referring to is the palynological evidence...
  
  Nichols, D. J. & Fleming, R. F. 1990. Plant microfossil record of
  the terminal Cretaceous event in the western United States and
  Canada. In: Sharpton, V. L. & Ward, P. D. eds., Global catastrophes
  in Earth history: an interdisciplinary conference on impacts,
  volcanism, and mass mortality.  Geological Society of America
  Special Paper, Boulder, 445-455.
  
  Johnson, K. R. & Hickey, L. J. 1990. Megafloral change across the
  Cretaceous-Tertiary boundary in the northern Great Plains and Rocky
  Mountains, U.S.A. In: Sharpton, V. L. & Ward, P. D. eds., Global
  catastrophes in Earth History: an interdisciplinary conference on
  impact, volcanism, and mass mortality. Geological Society of America
  Special Paper, Boulder, 433-444.
  
  ..which is taxonomically much-coarser a type of data. Some argue
  that a palynological extinction event took place (see above) while
  others suggest that the palynological turnover was either
  localized...
  
  Sweet, A. R. & Braman, D. R. 1992. The K-T boundary and contiguous
  strata in western Canada: Interactions between paleoenvironments and
  palynological assemblages. Cretaceous Research, 13, 31-79.
  
  Sweet, A. R., Braman, D. R. & Lerbekmo, J. F. 1990. Palynofloral
  response to K/T boundary events; A transitory interruption within a
  dynamic system.  In: Sharpton, V. L. & Ward, P. D. eds., Global
  Catastrophes in Earth History. Geological Society of America,
  Special Paper 247, 457-469.
  
  ..or very minor...
  
  Tschudy, R. H. 1984. Palynological evidence for change in
  continental floras at the Cretaceous-Tertiary boundary. In: A.,
  B. W. & Vancourvering, J. A. eds., Catastrophes and Earth History:
  The New Uniforitarianism.  Princeton University Press, Princeton,
  315-337.
  
  ..and even those who support the catastrophic interpretation for
  low-middle latitudes acknowledge that there was no palynological
  mass extinction at high latitudes...
  
  Johnson, K. R. & Greenwood, D. 1993. High-latitude deciduous forests
  and the Cretaceous-Tertiary boundary in New Zealand. Geological
  Society of America, Abstracts with Programs, 25, A-50.
  
  The way I read these data is that there was probably a localized
  ecological disturbance around K-T time in the western US, but that
  the taxic extent of this event is unclear. What is clear is that
  there is no K-T mass extinction in plants. Many of the plant groups
  that are (or soon will be) blooming outside your window would be
  represented in a Cretaceous landscape.
  
  > Besides, many of the above taxa such as the dinosaurs and
  > ammonites were doing well beforet the catastrophe and then
  > suddenly disappeared.
  
  Nada! There are 22 dinosaur families that make it into the
  Maastrichtian, but only 15 that make it to the Upper
  Maastrichtian. There are many more dino families in the Campanian,
  but I don't have that figure handy.  Dinosaurs were certainly
  declining throughout the upper Cretaceous. The lack of dino fossils
  unambiguously associated with impact debris has already been
  mentioned above as has the ammonite fossil record.
  
  Finally, it's not like there was nothing else going on the the
  uppermost Cretaceous. Eustatic sea level was changing...
  
  Haq, B. 1991. Sequence stratigraphy, sea-level change and
  significance for the deep sea. International Association of
  Sedimentologists, Special Publication, 12, 3-39.
  
  Haq, B., Hardenbol, J. & Vail, P. R. 1987. Chronology and
  fluctuating sea levels since the Triassic. Science, 235, 1156-1166.
  
  Volcanism was increasing...
  
  Courtillot, V. E. 1990. A volcanic eruption. Scientific American,
  263, 85-92.
  
  Courtillot, V., Jaeger, J.-J., Yang, Z., F=E9raud, G. & Hofman,
  C. in press.  The influence of continental flood basalts on mass
  extinctions: Where do we stand? In: Ryder, G., Fastovsky, D., et
  al. eds., Proceedings of the Conference on New Developments
  Regarding the K-T Event and Other Catastrophes in Earth
  History. Geological Society of America Special Paper, Boulder.
  
  Johnson, C. C. & Kauffman, E. G. 1996. Maastrichtian extinction
  patterns of Carribean province rudistids. In: MacLeod, N. & Keller,
  G. eds., The Cretaceous-Tertiary Mass Extinction: Biotic and
  Environmental Changes. W.  W. Norton & Co., New York, 231-274.
  
  ..and the overall climate was undergoing a series of short-term
  warming/cooling episodes from middle Maastrichtian onward...
  
  see E. Barrera's GSA abstracts for 1994 and 1995.
  
  All this was happening before your imapct! In short, I see no
  evidence for your assertions and a lot of published, peer-reviewed
  work by professional paleontologists to suggest you have your facts
  wrong. The idea that the K-T transition "started" with an impact has
  absolutely no foundation in paleontological data. If anything the
  impact occurred within a prolonged episode of environmental change
  that had already reduced the diversity of many clades, thus
  rendering them more susceptible to extinction by any and all
  mechanisms. More to the point, the patterns of extinction and
  survivorship we see in the fossil record do not seem to match
  reasonable biotic predictions derived from the various
  impact-related scenarios.
  
  I know you like the impact model and that's just fine. However,
  certain facts have been established and interpretations are not
  facts; especially when those interpretations are not even widely
  accepted. In both cases your posting doesn't do a very good job of
  summarizing this complex literature.

  Norm MacLeod

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