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Gerta Keller's last word. (I sincerely
hope not)
Smitten with failed impact-tsunami
theory
Please note: There will be two more contributions before
we close the Great Chicxulub Debate - one from Keller and
another from Smit, wrapping up their experiences of the
debate and pointing the way forward. Site Editor
Smit's final riposte to the Chicxulub Debate (Jan 5,
2004) concludes that "the K/T boundary impact and the
Chicxulub impact solidly remain one and the same". To draw
this conclusion he states that "all these conclusions and
evidence (referring to Keller and others' published
references and presented in these web debate pages) are
interpretations, not facts." He further states, "the large
body of contrary evidence … to the K/T impact-tsunami
hypothesis" (as presented by Keller and others) "contains
very little substance as well."
Smit's statements sum up the major problem why the K/T
impact mass extinction theory has continued for more than 20
years with no significant progress. It is the infatuation
factor with a very popular theory to the point where the
theory becomes fact and the real facts that don't fit the
theory are ignored, dismissed, or labeled "interpretation."
It has also become a game of showmanship where denial,
innuendo (and sometimes character assassinations) can take
the place of real scientific investigations, and where the
goal is to "outsmart your opponent".
Unfortunately, science loses in this game. Science
progresses by testing hypotheses through empirical
investigations, which either confirm or refute the
particular hypothesis. I believe Smit has turned this whole
process on its head by refuting the investigations and
resultant empirical data and treating the hypothesis as
fact.
More than 12 years ago Smit et al. (l992) proposed the
impact-tsunami theory to explain the siliciclastic deposits
separating the K/T boundary from the underlying impact
spherule ejecta deposits. At the time, the data were limited
to just one outcrop (El Mimbral) followed by a few other now
classic outcrops, such as El Penon. At the outset, the
impact-tsunami theory seemed to fit the field
investigations, at least on a superficial level. But
detailed investigations of more than 40 outcrops over the
past 10 years revealed critical evidence that invalidate
this theory for the northeastern Mexico region for which it
was developed (Adatte et al., l996; Keller et al., 1997;
2002, 2003; Ekdale and Stinnesbeck, l998).
We summarized the evidence in this web debate (see parts
I and II, as well as Adatte) and replied three times to
Smit's ripostes. Smit's final riposte has no new information
or substantive arguments. Instead, he simply rebuts or
dismisses each and every piece of evidence we presented as
"interpretation", as "insignificant", as "non-existent", or
counters by showing his own illustrations of what (he
believes) we show in our photos. Invariably, his
illustrations support his assertions, but make no sense and
bear no semblance to the data we present and show in our
photos. For example, he has done this repeatedly in the case
of the burrows of units 1, 2 and 3; he repeatedly claims
that all photos of j-shaped burrows are mirror images of one
and the same burrow; he repeatedly shows photos of crystals
and claims that these are what Keller mistakes as
foraminifera in the Chicxulub core, etc.
Here we summarize the critical data we presented in the
Chicxulub debate. For the details and illustrations the
reader is referred to the preceding web discussion
pages.
1. Bioturbation:
Fossil burrows are present within the three lithological
units that supposedly form the impact-tsunami deposits.
Their presence effectively rules out deposition over a
period of hours to days by a tsunami.
These fossil burrows have been widely documented from the
alternating sand-silt-shale layers of unit 3 where they are
abundant and diverse in several discrete layers (e.g.
Chondrites, Ophiomorpha, Planolites, Zoophycos). Chondrites
and Ophiomorpha burrows are truncated within unit 3 by
overlying sand beds El Penon (Chondrites) and Rancho
Canales (Ophiomorpha) respectively. In the massive sandstone
of unit 2, burrows (j-shaped spherule in-filled) are rare,
but present near the base where they are truncated by rapid
deposition of sand. Similar j-shaped spherule in-filled
burrows truncated at the top by erosion are observed in the
sandy limestone layer (SLL) that is present in the spherule
unit 1. No burrows are observed within the spherules layers
above and below the SLL (Ekdale and Stinnesbeck, l998;
Keller et al., l997; 2002, 2003, this web discussion).
These burrowed horizons represent repeated colonization of
the ocean floor during deposition of unit 3, and in unit 2
and 1 also indicate invertebrates lived on the ocean floor
repeatedly and disappeared at times of rapid sediment
influx. Sediment deposition therefore must have occurred
over an extended time interval that far exceeds a tsunami
event.
Our evidence of bioturbation has generally been ignored
by Smit. But faced with it in this debate he has tried hard
to discredit the findings by saying that they simply
represent root traces, cracks, flute casts, mud structures,
rusty scratches, and even wasp nests. More specifically, he
refutes the presence of the j-shaped spherule-infilled
burrows in units 1 and 2 as flame structures or mere rusty
scratches and shows a photo of something that looks like a
rusty scratch (Smit, Fig. 1c), which he says is the only
thing he observed. He seems oblivious to the fact that the
j-shaped burrows are up to 8cm long and 2cm wide and clearly
in-filled with spherules. They cannot be mistaken for rusty
scratches. He has also argued that the j-shaped burrows we
illustrate from units 1 and 2 are mirror images of one and
the same burrow, even though we show the photos are clearly
in their respective locations (the SLL and base of unit 2,
riposte II, fig. 18).
We illustrated two burrows, in both color and black and
white (as reproduced by Smit, Fig.1) one each from units 1
and 2, which Smit mistakenly assumed to represent four
burrows. He further claims that one burrow was mislabeled as
unit 3; if that is the case it is a typographic error.
Despite our evidence, despite our explaining his error, he
repeats that all images represent one and the same burrow,
one photo from a hand specimen and the counter image from
the field. It seems mind boggling to me that he can continue
this absurd argument with such certainty. Could it be it
because these burrows negate his tsunami theory?
Smit equally fervently argues that the multiple burrowed
horizons in unit 3 simply represent burrowing downwards
after the tsunami deposition. His "evidence" is his
interpretation in a block diagram showing Ophiomorpha
burrowing down to 1m and branching out. While it is true
that Ophiomorpha can burrow down to such depths, it does not
mean that all Ophiomorpha burrows can be interpreted as
originating at the top of unit 3. For example, we have shown
that at Rancho Canales the Ophiomorpha burrows are oblique,
not bifurcating, clearly different from the "vertical
bundles of tubes … that spread out horizontally" as
shown by Smit for El Penon, and clearly truncated within
unit 3. The organisms thus lived on the ocean floor during
unit 3 sediment deposition. Moreover, there is no question
that the small centimeter-long burrows of Chondrites within
various fine-grained layers of unit 3 represent in situ
burrowing during deposition of unit 3. The sole purpose for
denial of these facts seems to be the desire to fit data to
the impact-tsunami hypothesis.
We suggested that examining the microfossils within the
burrows as a simple test to determine whether burrowing
occurred from the Tertiary into the underlying strata of
unit 3. We conducted such tests and found only late
Maastrichtian microfossils within the burrows. Smit claims
that no Tertiary microfossils would be present because they
did not evolve for the first few thousand years after the
mass extinction. At El Mimbral, early Danian microfossils
are present in the cm above the red layer that contains the
K/T iridium anomaly (Keller et al., l994). In the most
expanded K/T boundary section at El Kef, the first Danian
species are present within the basal 3cm of the boundary
clay. Hence, burrowing by Ophiomorpha or any other large
invertebrate would have carried plenty of microfossils into
the burrows downward. None is observed.
2. Zeolite layers indicate volcanic influx
inconsistent with tsunami hypothesis:
Two distinct layers enriched in zeolites
(clinoptilolite-heulandite) are recognized near the base and
top of unit 3 in all sections examined (see Adatte et al.,
l996; Adatte this debate, Fig. 4). Additional
zeolite-enriched layers associated with smectite are also
observed in unit 1, as well as in the underlying late
Maastrichtian Mendez marls and the early Tertiary shales of
the Velasco Formation. These different zeolite enriched
layers are correlatable from section to section over a
distance of more than 300 km. An in situ-diagenetic origin
of these zeolites is unlikely because of their geographic
distribution and excellent corretability in different
lithologies, such as sands, silts, shales and marls (Fig.4).
These layers are therefore detritical in origin and indicate
discrete periods of volcanoclastic influx. Their widespread
presence within units 1 and 3 is further evidence that
deposition occurred over an extended time period that is
inconsistent with the impact-tsunami hypothesis.
Smit argues that the zeolite layers represent reworked
volcanic material from the bentonites in the Mendez marls
and are therefore not inconsistent with tsunami deposition.
How does a tsunami wave selectively remove a bentonite layer
and re-deposit it as discrete layer? The high energy waves
of a tsunami would rule out such discrete redeposition.
3. Sandy limestone layer in unit 1 inconsistent with
tsunami hypothesis:
A 10 - 20cm thick sandy limestone layer (SLL) is present
within the spherule unit 1 in most outcrops spanning an area
of 300km (Keller et al., l997; Adatte et al., l996). This
SLL contains some spherules at the base and top, but not
generally within. The SLL is burrowed as observed by the
presence of a j-shaped spherule-infilled burrow which is
truncated at the top. Whole rock and clay-mineral
compositions differ for the SLL and the cemented
spherule-rich layer above and below. (1) The spherule-rich
intercalations are primarily composed of calcite (up to
60%), decreased phyllosilicates, quartz and plagioclase;
intercalations of Mendez marls have the same composition.
(2) The thick SLL differs from these sediments by showing
lower calcite, but higher quartz, plagioclase, chlorite and
illite. This suggests distinctly different detrital influxes
during deposition of the SLL and the spherule rich layers.
It marks a change in the depositional environment from the
spherule layer above and below to sandy limestone deposition
with burrowing organisms on the ocean floor.
Smit argues that the SLL does not represent hemipelagic
deposition because it "is not even continuous over more than
10m." The SLL is present in unit 1 of most outcrops over an
area spanning 300km and hence can be regionally correlated.
The siliciclastic deposits (units 1 to 3) were generally
deposited in submarine channels. Exposures of
non-channelized sequences are rare, but when they do occur,
they also show a 10-20 cm thick sandy limestone layer (e.g.
La Sierrita). It seems that Smit's argument rests on
semantics, and essentially comes down to his interpretation
&endash; i.e., to call it a high-energy sandstone consistent
with tsunami deposition. Even so, what is this sandstone,
and the burrowing, doing within a spherule ejecta deposit
that is supposed to have been deposited within hours?
4. Multiple Spherule layers in Mendez marls:
The Mendez marl Formation below the spherule unit 1 was
not investigated until a few years ago (Stinnesbeck et al.,
2001, Keller et al., 2002, 2003). This investigation
revealed the presence of up to four additional spherule
layers interbedded in 10m to 12m of Mendez marls. Over 40
sections have been analyzed through detailed field
investigations and laboratory analyses.
Biostratigraphy indicates that deposition of all spherule
layers occurred within the Plummerita hantkeninoides zone
(CF1), which spans the last 300 ky of the Maastrichtian. The
lowermost spherule layer consistently is near the base of
this zone. In most outcrops the 2m to 4m between the
spherule layers consist of undisturbed marls. The multiple
spherule layers can be correlated. This has been
demonstrated particularly for the El Penon and Loma Cerca
sections, which are 25 km apart and show very similar
stratigraphic positions for the spherule layers interbedded
in the top 10-12 m of the Mendez Formation. We interpret the
stratigraphically lowermost spherule layer as the oldest
layer and the original spherule ejecta deposit with an age
of deposition about 300Ka prior to the K/T boundary. All
other spherule layers, including the spherules of unit 1 are
probably reworked from the original deposit at various times
during the latest Maastrichtian in association with sea
level changes.
Much has been made of some small (<10 m) isolated
slumps in the Mesa Juan Perez area, which was documented by
our team (Schulte et al., 2003). Smit has ceased on this
local small slump to interprete all multiple spherule layers
as slump deposits. In support he produced a photo of a
presumed slump next to perfectly layered Mendez marls at
Rancho Nuevo, which was disputed by Markus Harting (this
debate). Without any data of his own or any other evidence,
he concluded that all spherule layers could have been
deposited as slumps over a period of 10 years (why 10
years?); that none of the spherule layers can be correlated
over more than 10 m (why 10 m?), ignoring the data we
present for excellent correlation over 25 km.
5. Maastrichtian Foraminifera above suevite in
Yaxcopoil-1:
In the new Yax-1 core drilled in the Chicxulub crater, a
50 cm thick laminated micritic limestone with minor small
scale (2cm) oblique structures near the base and four thin
green glauconite layers disconformably overlie the suevite
breccia and underlie the K/T boundary. Late Maastrichtian
planktic foraminifera characteristic of the Plummerita
hantkeninoides zone CF1 have been observed and documented by
us in the laminated intervals (see fig. 21, 22 of Keller
reply II). Half a dozen foraminifer experts have confirmed
these images as bona fide Cretaceous planktic foraminifera.
Their presence in sediments above the suevite breccia and
below the K/T boundary effectively rules out a K/T age for
the Chicxulub impact.
In addition, magnetostratigraphy shows this interval to
have been deposited in Chron 29R prior to the K/T boundary,
and stable isotope data indicate normal late Cretaceous
values. Sediment analysis shows that the green layers are
of glauconitic origin and represent in situ formation over a
prolonged time interval. This data is consistent with the
earlier observations of a pre-K/T age of the oldest impact
spherule layer in NE Mexico discussed above.
Smit's response to this evidence is flat denial of its
existence. He claims that these images are dolomite rhombs
(We have already replied to this rather strange claim in
Keller et al. riposte II). He states that Arz has observed
some Albian foraminifera within these sediments, but that
they are not the same (there is no confirmation by Arz).
This denial seems ludicrous, especially when dolomite rhombs
are so totally different from foraminiferal images. It seems
to serve only one purpose &endash; to save the K/T impact
theory.
Smit proposes to test whether there are foraminifera
present by preparing polished thin sections. We have done so
a long time ago along with ultra-thin thin sections. We have
hundreds of images from these thin sections and some of the
images were already reproduced in these pages. Other
microfossil specialists have confirmed them as foraminifera.
According to Smit even Arz has identified foraminifera in
these sediments. Smit's call for an "impartial moderator to
perform this test" skirts the issue and seems to serve no
other purpose than to obfuscate and delay recognition that
Chicxulub predates the K/T boundary mass extinction. A
better approach to solve the disagreement is for other
foraminiferal specialists to examine these sediments, and to
examine the same interval in other UNAM cores taken in the
Chicxulub crater. Earlier studies of PEMEX cores have
already indicated that there is Late Maastrichtian sediments
above the impact breccia (see Ward et al., l995).
However, the issue of the age of the Chicxulub impact
does not solely rest on the presence of these planktic
foraminifera; there is also the magnetostratigraphy and the
stable isotopes. Moreover, the sedimentology itself does not
support backwash and crater infill for this interval.
6. Normal marine sedimentation or Backwash and
crater infill?
We have shown evidence that the critical 50cm interval
was deposited in a low energy but variable environment which
was interrupted repeatedly by long periods of very slow
deposition during which glauconite formed (see Keller et
al., riposte II).
Smit interprets this interval as high-energy backwash and
crater infill consistent with a post-impact tsunami event.
The prosecution rests…
We herewith conclude our part in this debate. No purpose
is served by continuing to re-hash the same issues over and
over again. The purpose of the Debate was to present the
facts and interpretations to the public. We never expected
to convince Jan Smit that his K/T impact-tsunami theory
failed and should be retired. Others will make that decision
for him. Our aim was to bring the varied evidence that
doesn't fit the K/T impact-tsunami theory into the open, to
let open-minded scientists and interested non-scientists see
what support there is for each side and to allow them to
draw their own educated conclusions. It is unfortunate that
there has been absolutely no input into this debate from the
K/T impact community that over the years has so strongly
supported the impact-tsunami theory. Why this deafening
silence? Why was there no voice in support for Jan Smit? The
controversy is not over. There is more evidence in the
pipeline and slowly but surely the true history of the
dinosaur extinction will unravel itself.
References:
Adatte, T., Stinnesbeck, W., and Keller, G., l996.
Lithostratigraphic and mineralogical correlations of
near-K/T boundary clastic sediments in northeastern Mexico:
Implications for mega-tsunami or sea level changes? Geol.
Soc. Am. Special Paper 307, 197-210.
Ekdale, A.A. and Stinnesbeck, W., l998. Ichnology of
Cretaceous-Tertiary (K/T) boundary beds in northeastern
Mexico. Palaios 13, 593-602
Keller, G., Stinnesbeck, W. and Lopez Oliva, J.G.,
l994. Age, deposition and biotic effects of the
Cretaceous/Tertiary boundary event at Mimbral, NE Mexico.
Palaios, 9, 144-157.
Keller, G., Lopez-Oliva, J.G., Stinnesbeck, W., and
Adatte, T., 1997. Age, stratigraphy and deposition of near
K/T siliciclastic deposits in Mexico: Relation to bolide
impact? Geological Society of America Bulletin 109,
410-428.
Keller, G., Adatte, T., Stinnesbeck, W., Affolter,
M., Schilli, L., and Lopez-Oliva, J.G., 2002. Multiple
spherule layers in the late Maastrichtian of northeastern
Mexico.Geol. Soc. Amer., Special Publication 356,
145-161.
Keller, G., Stinnesbeck, W., Adatte, T., and
Stueben , D., 2003a. Multiple impacts across the
Cretaceous-Tertiary boundary. Earth Science Reviews 62,
327-363.
Keller, G., Stinnesbeck, W., Adatte, T., and
Holland, B., Stueben, D., Harting, M., C. de Leon and J. de
la Cruz, 2003b. Spherule deposits in Cretaceous/Tertiary
boundary sediments in Belize and Guatemala. J. Geol. Society
of London, 160, 783-795.
Schulte, P., Stinnesbeck, W., Stueben, D., Kramar,
U. Berner, Z., Keller, G., Adatte, T., 2003. Fe-rich and
K-rich mafic spherules from slumped and channelized
Chicxulub ejecta deposits in the northern La Sierrita area,
NE Mexico. Int. J. Earth Sci. 92, 114-142.
Smit, J., Montanari, A., Swinburne, N.H.M., Alvarez,
W., Hildebrand, A., Margolis, S.,
Claeys, P., Lowrie, W., and Asaro, F., l992. Tektite
bearling deep water clastic unit at the Cretaceous-Tertiary
boundary in northeastern Mexico. Geology, v. 20, 99-103.
Smit, J., Roep, T.B., Alvarez, W., Montanari, A.,
Claeys, P., Grajales-Nishimura, J.M. and Bermúdez,
J., 1996. Coarse-grained, clastic sandstone complex at the
K/T boundary around the Gulf of Mexico: Deposition by
tsunami waves induced by the Chicxulub impact. Geological
Society of America Special Paper 307,151-182.
Stinnesbeck, W., Barbarin, J.M., Keller, G.,
Lopez-Oliva, J.G., Pivnik, D.A., Lyons, J.B., Officer,
C.B., Adatte, T., Graup,G., Rocchia, R., and Robin, E.,
l993. Deposition of channel deposits near the
Cretaceous-Tertiary boundary in northeastern Mexico:
Catastrophic or "normal" sedimentary deposits? Geology 21,
797-800.
Stinnesbeck, W., Keller, G., Adatte, T.,
Lopez-Oliva, J.G., and N. MacLeod, l996.Cretaceous-Tertiary
boundary clastic deposits in northeastern Mexico: impact
tsunami or sea level lowstand? In MacLeod N and Keller, G.,
(eds),Cretaceous- Tertiary Mass Extinctions. W.W. Norton
& Company, New York, 471-518.
Stinnesbeck, W., Schulte, P., Lindenmaier, f.,
Adatte, T., Affolter, M., Schilli, L., Keller, G., Stueben,
D., Berner, Z., Kramer, U. and J.G. Lopez-Oliva, 2001. Late
Maastrichtian age of spherule deposits in northeastern
Mexico: Implication for Chicxulub scenario. Canadian Journal
of Earth Sciences 38, 229-238.
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