PLEASE NOTE:
*
CCNet DIGEST, 28 July 1998
--------------------------
(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 Kuhns "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 Genuths
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 todays
scientific
scholarship than those which succeeded them during the 19th and
20th
centuries?
According to Genuth, the rejection of Newtons, Halleys
and Whistons
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
Gods 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. Genuths 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 Britains
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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