PLEASE NOTE:


*

CCNet DIGEST, 28 July 1998
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(1) REWRITING COMETARY HISTORY
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) NEW PAPERS ON THE CRETACEOUS-TERTIARY (K/T) EVENT


===================
(1) REWRITING COMETARY HISTORY

From ASTRONOMY & GEOPHYSICS: THE JOURNAL OF THE ROYAL ASTRONOMICAL
SOCIETY August 1998, 39(4), 34

REWRITING COMETARY HISTORY

Sara Schechner Genuth (1997) Comets, Popular Culture and the Birth
of Modern Cosmology, Princeton/Chichester: Princeton University
Press [ISBN 0-691-01150-8] hbk

Roberta J. M. Olson and Jay M. Pasachoff (1998) Fire in the Sky:
Comets and Meteors, the Decisive Centuries in British Art and
Science, Cambridge: Cambridge University Press [ISBN 0 521 630606]
hbk



Since Thomas Kuhn’s "The Structure of Scientific Revolutions", we know
that scientific paradigm shifts are generally followed by major
revisions of standard text-books and science history. These changes are
frequently documented as if the new paradigm gradually emerged from the
old view of the world. Science history thus tends to portray such
transformations as consistently progressive.

A rather different picture emerges from Sara Schechner Genuth’s book on
the birth of modern cometary theory. Here, astronomical knowledge
established some 300 years ago, regresses to such an extent that it
almost becomes extinguished in our own century. Newton and his
contemporaries were only too aware that gravitational attraction would
sooner or later cause comets to smash into the Sun, the Earth and the
other planets. Not surprisingly, cometary perturbations featured widely
in the works of Newton, Halley, Whiston and many of their
contemporaries. Yet between the early 19th and the late 20th
centuries, the theory of cometary catastrophes became a taboo in
science and academic discourse alike.

There is thus an essential question raised by “Comets, Popular Culture,
and the Birth of Modern Cosmology”: Why were cometary theories during
the 17th and 18th centuries more in line with today’s scientific
scholarship than those which succeeded them during the 19th and 20th
centuries?

According to Genuth, the rejection of Newton’s, Halley’s and Whiston’s
new astronomical comprehension of cosmic catastrophes was not due to
scientific reasoning or evidence, but invariably related to the
political opposition to cometary divination and the apocalyptic
interpretation of sacred and natural history. These popular activities
were the by-products of cosmology but, in the aftermath of the English
Civil War, were considered a persistent threat to the stability of
society.

As early as the Middle Ages, political authorities recognised the
threats posed by apocalyptic movements and cometary prophesies. Before
and during the Civil War, prognostication from comets (i.e. the
prediction of social and natural revolutions) became popular among
milleniarists, political radicals and the lower classes. The elite, by
contrast, chose to reject revolutionary astrology and folk beliefs
about comets. With the restoration of the Stuarts in 1660, the new
authorities cracked down on astrologers whose apocalyptic prophecies
were blamed for revolutionary incitement and political unrest.

Genuth claims that it was left to Newton to convert the alarming comet
lore into politically benevolent astrophysics. Popular folk belief was
fatalistic and held that comets augured civil disorder, social upheaval
and catastrophic destruction. For Newton, by contrast, comets were
bound by the universal laws of motion and were thus apparitions of
God’s design. By applying these laws, astronomers were able to
determine which comets might eventually punctuate the Earth. However,
since such information was prone to cause public alarm and,
consequently, likely to rekindle apocalyptic hysteria among the lower
classes, it was to be restricted to the scientific elite. As a result,
modern cosmology detached itself completely from popular conceptions
about comets and their hazards which were rejected as vulgar and
politically dangerous.

One could even go a step further and argue that the strategy to subdue
astronomical knowledge about the inevitability of cometary impacts
prevailed for almost 300 years; that is until astronomical
catastrophism was revived some 20 years ago. In fact, the strategy
was so successful that cometary perturbations did not feature in
astronomical research (let alone academic publications) until the
late 1970s. Genuth’s book provides convincing documents to suggest that
social and political reasons rather than hard scientific evidence led
the scientific elite to censure or conceal this knowledge. The book
will be most likely to rekindle the debate about the social factors
relating to astronomical research and paradigm building.

While Genuth draws heavily on and compares the astronomical views of
both the scientific elite (or what the author sometimes calls ‘high’
culture) and that of the lower classes (‘low’ or ‘popular’ culture),
“Fire in the Sky” is a rather traditional book of science history.
Olson and Pasachoff present some 160 paintings, photographs, drawings
and other works of art from the 18th and 19th centuries which document
the perception of comets and meteors among the elite of British
astronomers, artists and caricaturists. It is during this period that
the catastrophic bearing of cometary motion is overthrown and in which
the optimistic view of incessant natural, social and economic progress
replaced apocalyptic foreboding.   

This new confidence also brought about new attitudes towards comets,
leading to rather positive cometary connotations such as progress,
swiftness and brightness. Only eccentrics such as William Blake and
religiously inspired artists such as John Martin continued to portray
comets in an apocalyptic context. Yet in most cases, these isolated
paintings referred to past images (i.e. ancient Greek mythology, the
biblical flood, etc.)  rather than future perturbations.

In spite of the fact that 19th century Britain witnessed an
unprecedented record of spectacular comet apparitions, this traditional
view of comets failed to gain acceptance. Instead comets and meteors
increasingly pepper the satirical prints and caricatures of early 19th
century publications. Even party-political struggles between Tories and
Whigs become occasionally embroidered by cometary imagery.

"Fire in the Sky" focuses primarily on Britain’s ‘high’ culture and
hardly refers to documents which depict the cometary perceptions of
19th century ‘popular culture’. This limitation thus leads to a
somewhat restricted portrait of 18th and 19th century Britain. A review
of the cometary imagery in ‘popular culture’ would have shown that the
traditional and by now widely ridiculed view of comets as hazardous
celestial objects was maintained on the periphery throughout this
period of ‘enlightenment’. During the early 19th century, astronomers
such as David Milne and Wilhelm Olbers had even calculated that the
newly discovered comet Encke would – millions of years in the
future – inevitably impact the earth. It will take more time, more
research and further books to discover why this astronomical knowledge
was left ignored and unexploited for more than 150 years. Today, as
cosmic catastrophism has once again become a leading paradigm, both
books reviewed here testify to the need to re-think and re-write the
modern history of cometary astronomy.

Benny J Peiser

=======================
(2) NEW PAPERS ON THE CRETACEOUS-TERTIARY (K/T) EVENT

N. Lopez Martinez, L. Ardevol, M.E. Arribas, J. Civis, A. Gonzalez
Delgado: The geological record in non-marine environments around the
K/T boundary (Tremp formation, Spain). BULLETIN DE LA SOCIETE
GEOLOGIQUE DE FRANCE, 1998, Vol.169, No.1, pp.11-20

*) UNIVERSITY COMPLUTENSE MADRID, FAC CC GEOL, E-28040 MADRID, SPAIN

In the Ager basin and Benabarre area (southern Pyrenees, Spain), the
Cretaceous-Tertiary (K/T) boundary is recorded in a succession of
non-marine to coastal deposits (Lower Tremp Formation). Abundant
diverse dinosaur tracks have been found at two localities on top of an
estuarine sandstone body. A few meters above, grey marls at two
localities contain Palaeocene mammals and fish. Both levels are
correlated with the latest part of chron C29R. These data have led to
the location of the K/T boundary within a 3 m thick stratigraphic
interval with no major breaks in the sedimentation. A rapid fall in
delta(13)C content is recorded shortly after the WT boundary. The
delta(13)C curve does nor support the hypothesis of a gradual shift due
to volcanic activity. Both fossil vertebrates and isotope data are
compatible with an abrupt change in the continental ecosystems close to
the K/T boundary. Copyright 1998, Institute for Scientific Information
Inc.

====================
R. Coccioni*) and S. Galeotti: What happened to small benthic
foraminifera at the Cretaceous/Tertiary boundary? BULLETIN DE LA
SOCIETE GEOLOGIQUE DE FRANCE, 1998, Vol.169, No.2, pp.271-279

*) UNIVERSITY OF URBINO, INST GEOL, CAMPUS SCI, LOCALITA
   CROCICCHIA,I-612029 URBINO,ITALY

Benthic foraminiferal assemblages from the Cretaceous/Tertiary boundary
(KTB) of eight complete or near complete. land-based sections from
different depositional environments, record sudden and marked changes
of trophic structures and abundance which are bathymetrically related.
Deep-water assemblages were less severely affected by the KTB event
(KTBE) probably in consequence of increased organic matter nux to the
sea floor in response to oxygen deficiency in deep-and
intermediate-waters which counterbalanced the drop of oceanic primary
productivity. At the KTB the sea floor ecosystem experienced a
differentiation into two separate domains: a shallow-water ''epifaunal
domain'' and a deep-water ''infaunal domain''. Copyright 1998,
Institute for Scientific Information Inc.

=================
J. Roger, C. Bourdillon, P. Razin, L. LeCallonnec, M. Renard,
M.P. Aubry, J. Philip, J.P. Platel, R. Wyns, M. Bonnemaison:
Palaeoenvironmental and biotic changes across the Cretaceous/Tertiary
boundary in the Oman Mountains (in French). BULLETIN DE LA SOCIETE
GEOLOGIQUE DE FRANCE, 1998, Vol.169, No.2, pp.255-270

*) BUR RECH GEOL & MINIERES,SERV GEOL NATL,SGN12G,BP 6009,F-45060
   ORLEANS 2,FRANCE

Two new sites, revealing a record of the events at the K/T boundary,
have been recently discovered in the Oman Mountains at the eastern end
of the Arabian plate. In the Buraymi Basin. located at the northwestern
flank of the chain, the KIT boundary is intersected by a basinal facies
succession, whilst in the Sur area, the transition is illustrated
within a confined carbonate platform sequence. This period exhibits
important palaeoenvironmental and biotic changes which originated from
the conjunction of multiple factors. These came together over differing
intervals of time, i.e., long period of time, short time scale and
instantaneous event. At the scale of the long period of time (4 Ma)
stretching from late Maastrichtian to the Danian (P1c), the Oman
Mountains recorded profound modifications in terms of their
palaeogeographic context, undoubtedly linked to plate reorganisation.
This was initially shown by the emersion of the rudist platforms and
the flooding of the margins in the late, but not terminal,
Maastrichtian. This first tectonic event introduced an hemipelagic and
a turbiditic sedimentation. As a consequence, this episode created, at
the southern limb of the chain, the confined Murka sub-basin
characterised by a carbonate platform sedimentation. Because the
transition terminal Maastrichtian-earliest Danian correspond to a
period of tectonic quiescence, the sedimentation persisted through the
K/T boundary without any notable modification. A second tectonic
episode in the Danian P1b/P1c interval, accentuated the flooding of the
plate margins where basin deposits were accumulating. The renewal of
planktic foraminifera took place in stages suggesting a gradation of
palaeoecological conditions spread over a short time scale (1 to 2 Ma).
This gradation is marked by the succession of three waves of extinction
which took place from the late Maastrichtian to the KIT boundary.
Diversity of the benthic foraminifera then increased progressively from
subzone P1b onwards, showing the re-establishment of the ecosystem in
P1c. The iridium anomaly detected at the WT boundary at both sites
would tend to reinforce the hypothesis of a meteorite impact. the
effects of which would have added to these events that unfolded over a
longer rime scale. Copyright 1998, Institute for Scientific Information
Inc.

=====================
W.B. Yang and T.J. Ahrens: Shock vaporization of anhydrite and global
effects of the K/T bolide. EARTH AND PLANETARY SCIENCE LETTERS, 1998,
Vol.156, No.3-4, pp.125-140

*) CALTECH, SEISMOL LAB, LINDHURST LAB EXPT GEOPHYS, PASADENA, CA,
   91125

Shock vaporization experiments were carried out for 30% porous
anhydrite up to 76 GPa. Shocked fully or partially vaporized samples
interact with overlying LiF windows whose velocity histories are
monitored using a velocity interferometer to obtain pressure bounds for
incipient and complete vaporization for CaSO4. Experimental data and
thermodynamic calculations indicate that these shock pressures are 81
+/- 7 and 155 +/- 13 GPa for crystal anhydrite, and 27 +/- 1 and 67 +/-
6 GPa for porous anhydrite, respectively. A one-dimensional finite-
difference code was used to simulate the measured velocity profiles.
The vaporized products can be described by a simple Gruneisen thermal
equation of state where the effective Gruneisen parameter varies from
1.5 to 0.73 upon release from 76 to 25 GPa. Using the above criteria,
and recent lithic models of the impact site, the mass of degassed S has
been estimated from the Chicxulub impact. For asteroids of 10 and 20 km
in diameter impacting the Earth at 20 km/s, the mass of degassed S in
SO2 or SO3 is found to be 0.5 x 10(17) to 2 x 10(17) g. Simple
extrapolation of Sigurdsson's [H. Sigurdsson, Assessment of the
atmospheric impact of volcanic eruptions, in: V.L. Sharpton, P.D. Ward
(Eds.), Global Catastrophes in Earth History: An Interdisciplinary
Conference on Impact, Volcanism, and Mass Mortality, Geol. Sec. Am.
Spec. Pap. 247 (1990) 99-110.] formula yields a global cooling
prediction of greater than or similar to 10 degrees C. (C) 1998
Elsevier Science B.V. All rights reserved.

===================
W.J. Zinsmeister: Discovery of fish mortality horizon at the K-T
boundary on Seymour Island: Re-evaluation of events at the end of the
Cretaceous. JOURNAL OF PALEONTOLOGY, 1998, Vol.72, No.3, pp.556-571

*) PURDUE UNIVERSITY, DEPT EARTH & ATMOSPHER SCI,W LAFAYETTE,IN,47907

The discovery of a fish bone layer immediately overlying the K-T
iridium anomaly on Seymour Island, Antarctic Peninsula, which may
represent the first documented mass kill associated with the impact
event, together with new faunal data across the boundary has provided
new insight into events at the end of the Cretaceous. The utilization
of a geographical approach and a new graphical representation of range
data has revealed that events at the end of the Cretaceous were not
instantaneous, but occurred over a finite period of time. Although the
fish bone layer may contain victims of the impact event, the absence of
ammonites in either the iridium-bearing layer or the overlying fish
layer suggests that the extinction event at the end of the Cretaceous
was the culmination of several processes beginning in the late
Campanian. The impact was the proverbial ''straw that broke the camel's
back,'' leading to the extinction of many others forms of life that
might have survived the period of global biotic stress during the
waning stages of the Mesozoic if then had not been an impact. The
absence of mass extinction following catastrophic geologic events in a
biotic robust world, such as the Middle Ordovician Millbrig-Big
Bentonite volcanic event suggests that the biosphere is remarkably
resilient to major geologic catastrophes with mass extinction events
occurring only when there is a conjunction of geologic events none of
which might be capable of producing a global mass extinction by itself.
Copyright 1998, Institute for Scientific Information Inc.

========================
G. Keller*), T. Adatte, W. Stinnesbeck, D. Stuben, U. Kramar, Z.
Berner, L.Q. Li, K.V. Perch Nielsen: The Cretaceous-Tertiary transition
on the shallow Saharan Platform of Southern Tunisia. GEOBIOS, 1997,
Vol.30, No.7, pp.951-975

*) PRINCETON UNIVERSITY, DEPT GEOSCI,PRINCETON,NJ,08544

A multidisciplinary approach to the study of a K/T boundary section on
the Saharan Platform based on planktic and benthic foraminifera,
calcareous nannofossils, lithology, stable isotopes, mineralogy and
geochemistry reveals a biota stressed by fluctuating hyposaline,
hypoxic littoral and nearshore environments, productivity changes, and
a paleoclimate altering between seasonal warm to temperate and
warm/humid conditions. Benthic foraminifera indicate that during the
last 300 kyr of the Maastrichtian (CF1, Micula prinsii) deposition
occurred in a inner neritic (littoral) environment that shallowed to a
near-shore hyposaline and hypoxic environment during the last 100-200
kyr of the Maastrichtian. These conditions were accompanied by a
seasonal warm to temperate climate that changed to warm/humid
conditions with high rainfall, by decreasing surface productivity, and
significantly decreasing planktic and benthic foraminiferal species
richness. The K/T boundary is marked by an undulating erosional contact
overlain by a 10 cm thick sandstone layer which is devoid of any exotic
minerals or spherules. Their absence may be due to a short hiatus and
the fact that the characteristic clay and red layer (zone PO) are
missing. During the earliest Danian (Pla), low sea-levels prevailed
with continued low oxygen, low salinity, high rainfall, high erosion
and terrigenous sediment influx, accompanied by low diversity, low
oxygen and low salinity tolerant species. These environmental
conditions abruptly ended with erosion followed by deposition of a
phosphatic siltstone layer that represents condensed sedimentation in
an open (transgressive) marine environment. Above this layer, low sea-
levels and a return to near-shore, hyposaline and hypoxic conditions
prevailed for a short interval [(base of Plc(2))] and are followed by
the re-establishment of normal open marine conditions (inner neritic)
comparable to the late Maastrichtian. This marine transgression is
accompanied by increased productivity, and the first diversified Danian
foraminiferal assemblages after the K/T boundary event and represents
the return to normal biotic marine conditions. Though the WT Seldja
section represents one of the most shallow marginal sea environments
studied to date for this interval, it does not represent isolated or
atypical conditions. This is suggested by the similar global trends
observed in sea-level fluctuations, hiatuses, as well as faunal
assemblages. We conclude that on the Saharan platform of southern
Tunisia, longterm environmental stresses beginning 100-200 kyr before
the K/T boundary and related to climate, sea-level, nutrient, oxygen
and salinity fluctuations, were the primary causes for the eventual
demise of the Cretaceous fauna in the early Danian. The K/T boundary
bolide impact appears to have had a relatively incidental short-term
effect on this marine biota.Copyright 1998, Institute for Scientific
Information Inc.


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