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Cambridge Conference Digest - February 27, 1998

CAMBRIDGE-CONFERENCE DIGEST, 27 February 1998
---------------------------------------------

(1) SORRY PEOPLE, BUT I MADE A BIT OF A BOO-BOO
    Charles Darwin 

(2) A MODEL OF MASS EXTINCTION
    M.E.J. Newman, CORNELL UNIVERSITY

(3) EJECTA LAYER AT THE K/T BOUNDARY IN NEW JERSEY
    R.K. Olsson et al., RUTGERS STATE UNIVERSITY

(4) ROADBLOCKS ON THE KILL CURVE: TESTING THE RAUP HYPOTHESIS
    C.W. Poag, US GEOLOGICAL SURVEY

(5) MASS EXTINCTIONS AND THE SUN'S ENCOUNTERS WITH SPIRAL ARMS
    E.M. Leitch and G. Vasisht, CALTECH

(6) LOOKING AT THE K/T BOUNDARY IN THE WESTERN PYRENEES
    E. Apellaniz et al., EUSKAL HERRIKO UNIBERTSITATEA

(7) EVALUATING THE FLUCTUATION OF MASS EXTINCTIONS AND RECOVERY
    M.L. Droser et al., UNIVERSITY OF CALIFORNIA RIVERSIDE

(8) THE CRETACEOUS-TERTIARY BIOTIC TRANSITION
    N. Macleod et al., NATURAL HISTORY MUSEUM

(9) NONLINEAR DYNAMICS AND MASS EXTINCTIONS
    R.V. Sole et al., UNIVERSITY POLITECHNIC OF CATALUNYA

=====================================
(1) SORRY PEOPLE, BUT I MADE A BIT OF A BOO-BOO

From: Charles Darwin 

Hi folks,

Having followed your research and debates for some while, I think it's 
about time to confess that I no longer adhere to the main 
conclusions (attached below) of my controversial book published 
some 140 years ago. I am sure you will be lenient with me; after 
all, I used to be a fellow catastrophist in my early days. I've 
come to realise that I got it terribly wrong when I converted to 
Lyell's uniformitarian creed. After more than 90 years of sessions 
with my psycho-analyst, I now believe that the crisis which 
triggered this sudden conversion was not so much due to my 
relationship to my mother but rather caused by post-traumatic 
stress syndrom from which I suffered under the impact of the 
Chilean earthquake. So leave Oedipus out of the deabte.

Cheers, Charly

P.S. I have attached the main paragraph of my flawed theory which  
has now become merely of historical interest:

	"As all living forms of life are the lineal descendants of 
	those which lived long before the Silurian epoch, we may feel 
	certain that the ordinary succession by generation has never 	
	been broken, and that no cataclysm has desolated the whole 	
	world. Hence we may look with some confidence to a secure 	
	future of equally inappreciable length. And as natural 	
	selection works solely by and for the good of each being, all 	
	corporeal and mental environments will tend to progress towards 
	perfection" (On the Origin of Species by Means of Natural 	
	Selection: or the Preservation of Favoured Races in the 	
	Struggle for Life, 1859) 


=====================
(2) A MODEL OF MASS EXTINCTION

M.E.J. Newman: A model of mass extinction. JOURNAL OF THEORETICAL 
BIOLOGY, 1997, Vol.189, No.3, pp.235-252

CORNELL UNIVERSITY, CTR THEORY, RHODES HALL, ITHACA, NY, 14853, USA

In the last few years a number of authors have suggested that evolution 
may be a so-called self-organized critical phenomenon, and that 
critical processes might have a significant effect on the dynamics of 
ecosystems. In particular it has been suggested that mass extinction 
may arise through a purely biotic mechanism as the result of 
'coevolutionary avalanches'. In this paper we first explore the 
empirical evidence which has been put forward in favor of this 
conclusion. The data center principally around the existence of 
power-law functional forms in the distribution of the sizes of 
extinction events and other quantities. We then propose a new 
mathematical model of mass extinction which does not rely on 
coevolutionary effects and in which extinction is caused entirely by 
the action of environmental stress on species. In combination with a 
simple model of species adaption we show that this process can account 
for all the observed data without the need to invoke coevolution and 
critical processes. The model also makes some independent predictions, 
such as the existence of 'aftershock' extinctions in the aftermath of 
large mass extinction events, which should in theory be testable 
against the fossil record. (C) 1997 Academic Press Limited.

=========================
(3) EJECTA LAYER AT THE K/T BOUNDARY IN NEW JERSEY

R.K. Olsson*), K.G. Miller, J.V. Browning, D. Habib, P.J. Sugarman: 
Ejecta layer at the Cretaceous-Tertiary boundary, Bass River, New 
Jersey (Ocean Drilling Program Leg 174AX). GEOLOGY, 1997, Vol.25, No.8, 
pp.759-762

*) RUTGERS STATE UNIVERSITY, DEPARTMENT OF GEOLOGICAL SCIENCE, 
PISCATAWAY, NJ, 08855

A continuously cored borehole drilled at Bass River, New Jersey, 
recovered a Cretaceous-Tertiary (K-T) succession with a dcm-thick 
spherule layer immediately above the boundary. Below the spherule 
layer, the Cretaceous glauconitic clay is extensively burrowed and 
contains the uppermost Maastrichtian Micula prinsii calcareous 
nannofossil zone. Spherical impressions of spherules at the top of the 
Cretaceous indicate nearly instantaneous deposition of ejecta from the 
Chicxulub impact. The thickest ejecta layer shows clearly that a single 
impact occurred precisely at K-T boundary time. Above the spherule 
layer, the glauconitic clay contains the planktonic foraminiferal PO 
and Pa Zones, indicating (1) a complete K-T succession and (2) 
continuous deposition interrupted only by fallout of the ejecta layer. 
Clay clasts within a 6 cm interval above the spherule layer contain 
Cretaceous microfossils and may be rip-up clasts from a tsunami or 
possibly a megastorm event. Extinction of the Cretaceous planktonic 
foraminifers and burrowing organisms occurs abruptly at the K-T 
boundary. Thus, the Bass River K-T succession unequivocally links the 
Chicxulub bolide impact to the mass extinctions at the end of the 
Mesozoic. Copyright 1998, Institute for Scientific Information Inc.
=============================
(4) ROADBLOCKS ON THE KILL CURVE: TESTING THE RAUP HYPOTHESIS
 
C.W. Poag: Roadblocks on the kill curve: Testing the Raup hypothesis.
PALAIOS, 1997, Vol.12, No.6, pp.582-590

US GEOLOGICAL SURVEY, 384 WOODS HOLE RD, WOODS HOLE, MA, 02543

The documented presence of two large (similar to 100-km diameter), 
possibly coeval impact craters of late Eocene age, requires 
modification of the impact-kill curve proposed by David M. Raup. Though 
the estimated meteorite size for each crater alone is large enough to 
have produced considerable global environmental stress, no horizons of 
mass mortality or pulsed extinction are known to be associated with 
either crater or their ejecta deposits. Thus, either there is no fixed 
relationship between extinction magnitude and crater diameter, or a 
meteorite that would produce a crater of > 100-km diameter is required 
to raise extinction rates significantly above a similar to 5% 
background level. Both impacts took place similar to 1 - 2 m.y. before 
the ''Terminal Eocene Event'' (= early Oligocene pulsed extinction). 
Their collective long-term environmental effects, however, may have 
either delayed that extinction pulse or produced threshold conditions 
necessary for it to take place. Copyright 1998, Institute for 
Scientific Information Inc.
=====================
(5) MASS EXTINCTIONS AND THE SUN'S ENCOUNTERS WITH SPIRAL ARMS

E.M. Leitch and G. Vasisht: Mass extinctions and the sun's encounters 
with spiral arms. NEW ASTRONOMY, 1997, Vol.3, No.1, pp.51-56

CALTECH,PASADENA,CA,91125

The terrestrial fossil record shows that the exponential rise 
in biodiversity since the Precambrian period has been punctuated by 
large extinctions, at intervals of 40 to 140 Myr. These mass 
extinctions represent extremes over a background of smaller events and 
the natural process of species extinction. We point out that the 
non-terrestrial phenomena proposed to explain these events, such as 
boloidal impacts (a candidate for the end-Cretaceous extinction) and 
nearby supernovae, are collectively far more effective during the solar 
system's traversal of spiral arms. Using the best available data on the 
location and kinematics of the Galactic spiral structure  (including 
distance scale and kinematic uncertainties), we present evidence that 
arm crossings provide a viable explanation for the timing of the large 
extinctions. (C) 1998 Elsevier Science B.V.

================================
(6) LOOKING AT THE K/T BOUNDARY IN THE WESTERN PYRENEES

E. Apellaniz*), J.I. Baceta, G. Bernaola Bilbao, K. Nunez Betelu, 
X. Orue Etxebarria, A. Payros, V. Pujalte, E. Robin, and R. Rocchia:
Analysis of uppermost Cretaceous lowermost Tertiary hemipelagic 
successions in the Basque Country (western Pyrenees): evidence for a 
sudden extinction of more than half planktic foraminifer species at the 
K/T boundary. BULLETIN DE LA SOCIETE GEOLOGIQUE DE FRANCE, 1997, 
Vol.168, No.6, pp.783-793

*) EUSKAL HERRIKO UNIBERTSITATEA,ZIENTZI FAK,ESTRATIG & PALEONTOL 
SAILA, 644 POSTAKUTXA, BILBAO, BASQUE COUNTRY, SPAIN

This paper summarises our current knowledge about 21 sections across 
the K/T boundary from the Basque Country (western Pyrenees), all of 
them comprising intermediate-deep basinal facies. This study allowed us 
to establish that Sopelana III and Bidart are the best sections for 
analysing the extinction of the planktic foraminifers at the K/T 
boundary. Detailed analyses of planktic foraminifers from four new 
sections allow us to differentiate four biozones, one at the end of the 
Cretaceous and three at the beginning of the Tertiary. These analyses 
further show that 63 Upper Maastrichtian planktic foraminifers species 
reached the boundary where 33 species became extinct. The study also 
shows that some species decrease markedly in abundance in the last few 
metres of the Cretaceous prior to the extinction event which could be 
related to environmental changes at the end of the Maastrichtian. More 
than 50 % of the planktic foraminifers, that is 33 species, became 
extinct at the end of the Cretaceous. However, most of the extinct 
species were rare and only about 20 % of the total Cretaceous 
assemblages are involved in the extinction event. The 30 surviving 
species, that is less than 50 % of the Cretaceous species, later 
disappear through the Pr. longiapertura and P. pseudobulloides biozones 
of the beginning of the Tertiary. Above the K/T boundary, samples are 
far poorer in planktic foraminifer specimens than those from the 
uppermost Maastrichtian and include 16 Tertiary species. Moreover, 
together with this extinction event there are impact markers (iridium 
and Ni-rich spinels), as well as a high concentration of soot at the 
beginning of the Danian at the Sopelana III section. This strengthens 
the hypothesis of a causal link between the impact and WT extinctions.
Copyright 1998, Institute for Scientific Information Inc.

========================
(7) EVALUATING THE FLUCTUATION OF MASS EXTINCTIONS AND RECOVERY

M.L. Droser*), D.J. Bottjer, and P.M. Sheehan: Evaluating the 
ecological architecture of major events in the Phanerozoic history of 
marine invertebrate life. GEOLOGY, 1997, Vol.25, No.2, pp.167-170

*) UNIVERSITY OF CALIFORNIA RIVERSIDE, DEPARTMENT OF EARTH 
SCIENCE, RIVERSIDE,CA,92521

Paleoecological changes associated with Phanerozoic mass extinctions 
and radiations can be categorized into four nonhierarchical, 
nonadditive levels. First-level changes include colonization of a new 
ecosystem. Structural changes within an established ecosystem represent 
the second level, changes within an already established ecological 
structure are the third level, and taxonomic changes within a community 
represent the fourth level. Applying these levels to the Ordovician 
radiation, end-Ordovician extinction and Silurian recovery, as well as 
the end-Permian extinction and Triassic recovery, demonstrate that 
paleoecological changes associated with these major events can be 
evaluated and compared in a more rigorous manner than previously done. 
Results of this analysis demonstrate that use of these levels indicates 
that the relative magnitude of an event as measured by taxonomic 
criteria may be decoupled from its paleoecological significance. 
Copyright 1998, Institute for Scientific Information Inc.

========================
(8) THE CRETACEOUS-TERTIARY BIOTIC TRANSITION

N. Macleod*), P.F. Rawson, P.L. Forey, F.T. Banner, M.K. Boudagher 
Fadel, P.R. Brown, J.A. Burnett, P. Chambers, S. Culver, S.E. Evans, C. 
Jeffery, M.A. Kaminski, A.R. Lord, A.C. Milner, A.R. Milner, N. Morris, 
E. Owen, B.R. Rosen, A.B. Smith, P.D. Taylor, E. Urquhart, J.R. Young: 
The Cretaceous-Tertiary biotic transition. JOURNAL OF THE GEOLOGICAL 
SOCIETY, 1997, Vol.154, No.Pt2, pp.265-292

*) NATURAL HISTORY MUSEUM, DEPT PALAEONTOLOGY, CROMWELL RD, LONDON SW7 
5BD, ENGLAND

Mass extinctions are recognized through the study of fossil groups 
across event horizons, and from analyses of long-term trends in 
taxonomic richness and diversify. Both approaches have inherent flaws: 
and data that once seemed reliable can be readily superseded by the 
discovery of new fossils and/or the application of new analytical 
techniques. Herein the current state of the Cretaceous-Tertiary (K-T) 
biostratigraphical record is reviewed for most major fossil clades, 
including: calcareous nannoplankton, dinoflagellates, diatoms, 
radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, 
brachiopods, molluscs, echinoderms, fish, amphibians, reptiles and 
terrestrial plants (macrofossils and palynomorphs). These reviews take 
account of possible biasing factors in the fossil record in order to 
extract the most comprehensive picture of the K-T biotic crisis 
available. Results suggest that many faunal and floral groups 
(ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were 
in decline throughout the latest Maastrichtian while others (diatoms, 
radiolaria, benthic foraminifera, brachiopods, gastropods, fish, 
amphibians, lepidosaurs, terrestrial plants) passed through the K-T 
event horizon with only minor taxonomic richness and/or diversity 
changes. A few microfossil groups (calcareous nannoplankton, 
dinoflagellates, planktonic foraminifera) did experience a turnover of 
varying magnitudes in the latest Maastrichtian-earliest Danian. 
However, many of these turnovers, along with changes in ecological 
dominance patterns among benthic foraminifera, began in the latest 
Maastrichtian. Improved taxonomic estimates of the overall pattern and 
magnitude of the K-T extinction event must await the development of 
more reliable systematic and phylogenetic data for all Upper Cretaceous 
clades. Copyright 1998, Institute for Scientific Information Inc.

=============================
(9) NONLINEAR DYNAMICS AND MASS EXTINCTIONS

R.V. Sole*), S.C. Manrubia, M. Benton, P. Bak: Self-similarity of 
extinction statistics in the fossil record. NATURE, 1997, Vol.388, 
No.6644, pp.764-767

*) UNIVERSITY POLITECHNIC OF CATALUNYA, DEPT PHYS FEN, CAMPUS NORD, 
MODUL B4,ES-08034 BARCELONA,SPAIN

The dynamical processes underlying evolution over geological timescales 
remain unclear. Analyses of time series of the fossil record have 
highlighted the possible signature of periodicity in mass extinctions, 
perhaps owing to external influences such as meteorite impacts. More 
recently the fluctuations in the evolutionary record have been proposed 
to result from intrinsic nonlinear dynamics for which self-organized 
criticality provides an appropriate theoretical framework. A 
consequence of this controversial conjecture is that the fluctuations 
should be self-similar, exhibiting scaling behaviour like that seen in 
other biological and socioeconomic systems. The self-similar character 
is described by a 1/f power spectrum P(f), which measures the 
contributions of each frequency f to the overall time series. If 
self-similarity is present, then P(f) approximate to f(-beta) with 0 < 
beta < 2, This idea has not been sufficiently tested, however, owing to 
a lack of adequate data. Here we explore the statistical fluctuation 
structure of several time series obtained from available 
palaeontological data bases, particularly the new 'Fossil Record 2'. We 
find that these data indeed show self-similar fluctuations 
characterized by a 1/f spectrum. These findings support the idea that a 
nonlinear response of the biosphere to perturbations provides the main 
mechanism for the distribution of extinction events. Copyright 1998, 
Institute for Scientific Information Inc.

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