(3) WHY BIOSTRATIGRAPHERS DON'T AGREE WITH JAN SMIT
Gerta Keller <gkeller@Princeton.EDU>
Dear Benny
Jan Smit (CCNet Jan. 23) brings a spirited defense of Schulte et al.(CCNet
Jan. 12) and his own work by rehashing old arguments (because
the "old arguments" are still correct) he has made time and time
again - arguments which have already been demonstrated ("demonstrated" only
by Keller and associates, who follow her blindly) to contradict empirical evidence in various
publications. Here I will only address his claim that is relevant to the Schulte
et al. paper, namely that the KT boundary at Brazos is correctly placed at
the base of the event deposit based on the presence of Chicxulub spherules.
His many other claims, including sedimentation, sea level systems tracts and
KT spherules being the same as Chicxulub spherules, make little sense and have no scientific basis (moot qualifications without any basis).
On CCNet Jan. 24 he continues pulling the wool over non-experts eyes by attempting
to denigrade paleontologists (as Luis Alvarez has done in the past) by labeling
them as little more than drawing "their conclusions behind the microscope,
fully neglecting sedimentological and field aspects." In this derogatory
statement he includes anyone who disagrees with him - the sedimentologists,
mineralogists and geochemists along with the biostratigraphers (Ho ho, not all of them, just your team consisting of lip servants. The vast majority agrees with me,
only some biostratigraphers don't) . He puts himself up as expert in
all ( I worked with many experts in all of these fields)
, but has done no research (nonsense, I have done a lot of research, but if it turns up no new facts, why distort them and present them as new?)
and published no studies on biostratigraphy for more than 20 years,
nor has he published any in-depth studies on sedimentology, mineralogy
or geochemistry comparable to the ones he derides ( On
the contrary, I find Peter Schultes PhD thesis an excellent and in depth study
of the KT boundary deposits in Mexico. He decided to quit with your team because you changed his data in his PhD thesis), Instead, he accuses
with innuendo and slander the detailed and serious research ( I
do indeed, as such research is based
on amateurish, below standard sedimentological observations) done by multidisciplinary
teams of experts as not knowing what they are doing whenever the results
do not agree with his own (Uuuuuh,
that's normal, is n't it? If research does not agree on what you are working
on since 1974, you start wondering if you are right or wrong. I checked and
rechecked my results, and they came out like before. So I started to examine
the science of the other party, and found serious and fatal flaws in that
research) (that includes his comments on sedimentology, mineralogy,
sea level, and geochemistry in CCNet Jan. 23).
In todays CCNet he raises a red herring by asking "Why can biostratigraphers
not agree on the K-T boundary?" In fact, biostratigraphers do agree (wishful thinking, look at the K/T boundary definition paper in Episodes by Molina et al 2008!) on the placement of the K-T boundary.
More than any other boundary, the K-T boundary is very easily identified
and there is hardly ever any disagreement among biostratigraphers on its
placement (finally we agree, but there is one region where this debate is all about: the Gulf of Mexico
near the Chicxulub impact, and there Keller is dead wrong). It is only when ideology and circular
reasoning interfere that there are disagreements. Smit uses circular
reasoning by claiming that Chicxulub is the K-T impact, therefore wherever
Chicxulub ejecta is found must be the K-T boundary. In the process he
dismisses the geochemical, lithological and stratigraphic criteria ( Nonsense, I adressed specifically these criteria (mass-extinction, iridium
anomaly, base of boundary clay) with regards to the K/T boundary)
- while at the same paying them lip service as in his CCNet comment.
Let us first analyze Smit's arguments in CCNet Jan. 24. He states that "What
biostratigraphers forget is that boundary stratotypes are NOT defined on
biostratigraphic criteria, but are a "golden spike" in a sedimentary
succession, chosen (in el Kef, not elsewhere)
on lithological criteria." Evidently Smit assumes (I never implied that) that lithological changes ( I said criteria, not changes) are time correlative, but anyone who has taken Geology 101 knows
that (all?) lithological changes are time
transgressive (but here below you make the exception?!).
A lithological succession changes with the local environment - it can therefore
not become a globally correlateable boundary (that is totally beyond the point, you don't correlate the K/T boundary by lithological criteria) deposits.
Only when a lithological change is induced by a global event (First all lithological changes are time transgressive, and now
lithological changes are not time-transgressive?),
such as the KT clay layer, the KT carbon-13 shift, the late Cenomanian carbon-13
shift in association with global anoxia and organic-rich sediments, can
lithology be used as one of the criteria in conjunction with the geochemical
markers ( I don't follow this, this is exactly what
I meant, and to define the K/T boundary )
However, even the KT clay layer and basal red layer with its Ir anomaly is
dependent on local environments and its absence doesn't necessarily mark the
absence of the KT boundary. By Smit's argument (No, I said it is defined at the base of the clay at el Kef. Please read!) the KT boundary must always
be placed at the base of the KT clay layer (In the
GSSP at el Kef it is defined at the base of the clay layer. period. But anywhere else you have to use your brains, correlation tools
and common geological sense. As it happens, these correlation tools invariably lead to a position
of the K/T boundary at the base of a clay layer, as Keller admits above, except in the Gulf of Mexico).
All biostratigraphers agree and follow this practice, especially if this clay
layer also records an Ir anomaly and the global shift in carbon-13 values
(so what is the point?, we do the same).
But let us examine whether Smit and Schulte et al. follow this practice as
they proclaim. For example, at Brazos there is no distinct KT clay layer
(not true. Claylayer G and base of I, are extremely poor in biota, and poor in carbonate (<20%). That is not obvious in the field because carbonate content is below
30% in all adjacent non-event beds).
But an Ir anomaly is present above (wrong, not above, but
in the top of the event bed. An important distinction, because it makes the iridum anomaly part of the event!)
the event deposit coincident with the first Tertiary species (wrong again) and a mm thin
rust colored sandstone layer (Rocchia et al., l996) (wrong again. Rocchia showed this rust colored sandstone layer is compared to directlty adjacent layers
poor in iridium) .
In addition, the global carbon-13 shift coincides (Not
exactly, they are separated) with the Ir anomaly and biostratigraphic placement (your biostratigraphic placement, at the Kef GSSP these markers are above the K/T boundary) of the KT boundary.
Yet, Smit and Schulte et al dismiss these accepted markers (wrong again, we use these markers) and
place the KT boundary at the base of the event deposits on the sole basis
that they contain Chicxulub spherules (Nope, it coincides
with the mass-extinction, which happens at el Kef GSSP exactly at the K/T boundary, contrary to Keller's markers) .
They do the same in Mexico's sections where a clay layer and thin red layer
with Ir anomaly (wrong again, that red layer is a fine
sand, and on the contrary poor in iridium like at Brazos river) is present above the event deposits (wrong again, it is in the top of the event deposit),
such as at El Mimbral, La Sierrita, La Parida and others. This KT clay and
Ir anomaly also coincides (Nope, your abundant foraminifers
in a micrite mud have already disappeared below the event bed ) with
the mass extinction in planktic foraminifera and the first appearance of Tertiary
species within a few cm above it (wrong again, and sloppy. In all these sites the last normal Cretaceous beds are all below the event bed). But as at Brazos, Smit and Schulte et al
place the KT boundary at the base of the event deposit on the basis that the
presence of reworked Chicxulub spherules there marks this as the KT boundary (wrong again, we took the mass-extinction level).
They ignore Smit's (Smit ignores Smit??) much touted identifying criteria (CCNet Jan. 24) and the
fact that the original Chixulub spherule ejecta is interbedded in undisturbed (wrong again. Schulte and I revisited these outcrops, and beyond doubt and exception, these "original" Chicxulub spherule ejecta layers are all discontinuous slumped) marine marls 4-5 m
below the event deposit (BBC Horizon 2004: What didn't kill the dinosaurs).
It is clear that while paying lip service to the defining criteria, they in
fact only use their belief that the presence of Chicxulub spherules at the
base of the event deposit places the KT boundary there because they assume
that Chicxulub is the KT impact. The age of this impact, however, appears
to predate the KT by about 300 ky (Keller et al., 2002, 2003, 2004a,b) (based on what criterion??).
Smit and Schulte et al. thus conveniently dismiss lithological and geochemical
data when it doesn't fit their belief of where the boundary should be placed
to be consistent with the hypothesis that the Chicxulub impact is the KT killer.
What about Smit's slander of biostratigraphers? Who use only subjective criteria
(since when is the interpretation behind a microscope
a proven fact?? it remains a human interpretation!), who can never
agree on first and last appearance datums? Smit trots out the brief keywords
on the KT as selected by Jim Ogg for the latest ICS web page. These keywords
include the Ir anomaly, the mass extinction in the major microfossil groups
and dinosaurs (the latter is especially controversial and not a defining criteria
since few dino bones if any can be found at the KT boundary). Jim Ogg obviously
didn't include all marker criteria for the KT boundary in his keywords. Notably
absence is the carbon-13 shift, and the first appearances of Tertiary species,
which are indeed key bio- (can't be, they first occur
5 cm above the KT boundary!) and chemo-markers of the KT boundary.
But neither are Chicxulub impact spherules mentioned as identifying citerion
as Smit would have us belief.
Smit takes Oggs keywords as support to dismiss any and all biostratigraphers
who employ the first appearances of Tertiary species as one of the markers
of the KT boundary at Brazos - that indeed includes every study done by microfossil
biostratigraphers to date. Even Schulte et al.s dinoflagellate expert on his
team, Michael Prauss (see CCNet, Jan. 23), who excused himself from this paper.
This agreement (??among who) among biostratigraphers for the placement of the KT boundary
in the Brazos section alone shows that evidently biostratigraphy works very
well across different microfossil groups. The close coincidence of the first
Tertiary species with the carbon-shift and the Ir anomaly - all above the
event deposits - makes it rather clear that the KT boundary is not at the
base of the event deposits.
Smits erroneously claims that:" They all five (Prauss, Tantawy, Keller,
Adatte, Harting) mistakenly stress that the ONLY criteria based on first occurrences
of Paleocene biota should be used.." This is at best misrepresentation
by Smit since all biostratigraphers have made it clear that faunal turnovers
from Cretaceous to Paleocene assemblages and the carbon-13 shift mark the
placement of the boundary,
Biomarkers, first and last appearances of species and acmes, appropriately
tested globally form the basis of biostratigraphy and age dating in conjunction
with paleomagnetic and radiometric dates. At the K-T boundary, the mass extinction
of tropical and subtropical planktic foraminifera marks a unique event. Equally
unique is the first appearance of Tertiary species in foraminifera, as well
as nannofossils and dinoflagellates. Smit stated that this occurs within the
first 5 cm above the extinction horizon and Ir anomaly at El Kef, which is
indeed very close (but not close enough!). In
fact, the first Tertiary forams appear already in the first 1 cm of the KT
clay in the smaller than 63 micron size fraction (Keller et al., 1995; 2002)
(Keller claims so, but she is the only one finding them
there) and coincident with the carbon-13 shift. Yet he exclaims: "Where
she recognizes that first appearance of Danian species DO NOT coincide with
the K/T boundary!?" Evidently he has not kept up with biostratigraphic
KT studies over the past decades (I am not the only one who does not accept your identifications, poorly figured specimens, and acceptation of dolomite crystals for foraminifers).
This is also evident in his comment: "As member of the subcommission
on the K/T GSSP, I pledged for NOT ACCEPTING the first appearance of e.g.
E. eugubina, of C. primus, knowing that these markers first occur 4-25 centimetres
above the iridium anomaly..." (Disclosure: I was also a member of that
subcommission). No biostratigrapher proposed on that commission that the first
appearance of P. eugubina mark the KT boundary. The first appearance of this
species has always been (at least for two decades) the index fossil for the
P0/Pla boundary in the early Danian! Smit's claim makes it clear that he is
not familiar with biostratigraphy - while at the same time dismissing it.
If Smit had carefully read Tantawy's comment on CCNet, he would also have
seen that C. primus is not a KT defining criterion. But a host of first and
last appearances of species and faunal turnovers are including the nannofossil
"Biantholithus sparsus the calcareous dinoflagellate Thoracosphaera operculata,
the sudden change in nannofossil assemblage, the last appearance of Ankhangelskiella
cympiformis and Micula decussata and/or the first appearance of Cyclagelosphaera
alta." Is Smit really so out of it with the current status of biostratigraphy?
Or just arrogant in dismissing all that doesn't fit his hypothesis? (you can scream and wriggle, but all said and done, the K/T boundary exactly coincides at the el Kef GSSP with the easily observable mass-extinction of the calcareous planktic biota, and NOT, I repeat NOT, with the first appearance of new Paleocene species). They approximate, but do NOT coincide!)
Based on the above arguments Smit states "Biostratigraphically, the K/T
boundary is therefore better defined and approximated by the major extinction
horizon, and this level is in Brazos river below the event beds." There
is just one small problem with this criterion at Brazos - there is no conventional
mass extinction. (Not if you solely rely on microsope
observations, ignoring lithological properties and abundance patterns)
Planktic foraminifera, define this mass extinction in marine fossils with
all tropical and subtropical species extinct (2/3 of the total assemblage)
by KT time and the survivorship of environmentally tolerant taxa. At Brazos,
biotic stress is very high through the late Maastrichtian because the area
was a very shallow sea (less than 80m estimated by Schulte et al) excluding
most specialized species. In this environment species diversity is therefore
very low, 20-30 species in any given sample below the event bed, as compared
with 55-60 species in normal marine environments (Keller, l989). Some specialized
species (e.g., globotruncanids and rugoglobigerinids) are sporadically present
and these disappear at the unconformity at the base of the event deposit (reading this
I dropped from my chair in astonishing amazement! This very disappearance is
therefore equal to the -by Keller- much touted mass-extinction of tropical and
specialized species. What better criterion can you use to define the KT boundary?
It only so happens that that coincides with the base of the event bed, as
Schulte and Smit have said from the beginning, and as Keller here admits).
The event deposit and sediments above it were deposited in even shallower
seas leading to even greater biotic stress, as evident by the sharp increase
of benthic species in the benthic/planktic ratio. In this high-stress environment
the disappearance of the rare and sporadic specialized species at the unconformity
below the event deposit cannot be assumed to represent the KT mass extinction
as Smit claims (and why not? in the deep Gulf of Mexico this "biotic stress" does not exist I presume, yet representatives of specialized foraminifers washed in from there do not occur above the event bed).
In contrast, the carbon-13 shift and Ir anomaly both of which coincide with
the first appearance of Danian planktic foramifera, nannofossils and dinoflagellates
and faunal turnovers from Cretaceous to Paleocene assemblages well above the
event deposit reliably mark the KT boundary. Prauss, Tantawy and I have independently
studied the microfossils in the core KT1/KT2 of Schulte et al. and found that
the boundary is coincident with the carbon-13 shift at 1.6 m above the event
deposit. Thus, three independent studies based on different microfossil groups
all agree on the placement of the KT boundary. They agree because the KT faunal
and floral turnovers and the carbon-13 shift are unique. The same was observed
in other sequences at Brazos (e.g., KT3 core, and CM outcrops, Keller, l989;
Barrera and Keller, l990). Smit and Schulte et al. conveniently ignore this
evidence.
Now consider that reworked Chicxulub ejecta is always well below the KT and
at the base of the event deposit. Based on the empirical evidence this is
a clear case of two separate events - the KT and Chicxulub impacts.
(The funny thing is, take away the event deposits (incorporating those slumped spherule beds within the event beds), and
our K/T boundary and Kellers K/T boundary almost exactly coincide. The event
deposits are most likely caused by a series of tsunamis, with possibly a few
storm deposits related to the event, lasting a few weeks of time at most. These
few weeks will not be discernible in other K/T sequences, where no such beds
interfere. So what are we talking about, a difference of a few weeks in geological
time?)
Gerta Keller, Department of Geosciences, Princeton University
gkeller@princeton.edu
References:
Barrera, E., and Keller, G., l990. Stable isotope evidence for gradual environmental
changes and species survivorship across the Cretaceous-Tertiary boundary.
Paleoceanography 5(6), 867-890.
Keller, l989. Extended Cretaceous/Tertiary boundary extinctions and delayed
population change in planktic foraminifera from Brazos River, Texas. Paleoceanography
4, 287-332.
Keller, G., Li, L. and MacLeod, N., 1995. The Cretaceous/Tertiary boundary
stratotype section at El Kef, Tunisia: How catastrophic was the mass extinction?
Paleogeogr., Paleoclimatol.,
Paleoecol., 119: 221-254.
Keller, G., Adatte, T., Stinnesbeck, W., Luciani, V., Karoui, N., Zaghbib-Turki,
D., 2002. Paleoecology of the Cretaceous-Tertiary mass extinction in planktic
foraminifera. Paleogeogr., Paleoclimatol., Paleoecol., 178, 257-298.
Keller G., Stinnesbeck W., Adatte T. and Stueben D. 2003. Multiple impacts
across
the Cretaceous-Tertiary boundary. Earth-Science Reviews 1283: 1-37.
Keller, G., Adatte, T., Stinnesbeck, W., Rebolledo-Vieyra M., Urrutia Fuccugauchi,
J., Kramar, G., and Stueben, D., 2004a. Chicxulub predates the K/T boundary
mass extinction. Proceedings of the National Academy of Sciences 101, 3753-37-58.
Keller, G., Adatte, T., Stinnesbeck, W., Stueben, D., Berner, Z., Kramar,
U., Harting, M., 2004b. More evidence that the Chicxulub impact predates
the K/T mass extinction. Meteoritics & Planetary Science 39 (7), 1127-1144,
Keller, G., Adatte, T., Berner, Z., Harting, M., and Stueben, D., 2005. Chicxulub
impact predates K-T boundary in Texas and caused no mass extinction. 7th
International Symposium on the Cretaceous 5-9 Sept. 2005, University of Neuchatel,
Switzerland, Scientific Program and Abstracts, P. 118-119.
Remane, J., Keller, G., Hardenbol, J., Ben Haj Ali, M., l999. Report on the
international workshop on Cretaceous-Paleogene transitions. Episodes 22(l),
47-48.
Rocchia, R., Robin, E., Froget, L. and Gayraud, J., l996. Stratigraphic distribution
of Extraterrestrial markers at the Cretaceous-Tertiary boundary in the Gulf
of Mexico Area: Implications for the Temporal Complexity of the event. In:
The Cretaceous-Tertiary Event and other Catastrophes in Earth History, Geol.
Society of America, Special Paper 307, P. 279-286.
Schulte, P, Speijer, R., Mai, H., Kontny, A. (2006) The Cretaceous-Paleogene
(K-P) boundary at Brazos, Texas: Sequence stratigraphy, depositional events
and the Chicxulub impact. Sedimentary Geology, 184, 77-109
Gerta Keller
Department of Geosciences
Princeton University
Princeton NJ 08544, USA
email: gkeller@princeton.edu
phone: (609) 258-4117
fax: (609) 258-1671
Website:
http://geoweb.princeton.edu/research/Paleontology/paleontology.html
The Chicxulub Debate:
http://geoweb.princeton.edu/people/faculty/keller/chicxulub.html
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