Meteoritics & Planetary Science 39, Nr 6, 787–790 (2004)
Abstract available online at http://meteoritics.org

787 © Meteoritical Society, 2004. Printed in USA.

The Chicxulub Scientific Drilling Project (CSDP)

Jaime URRUTIA-FUCUGAUCHI,1 Joanna MORGAN,2 Dieter STÖFFLER,3 and Philippe CLAEYS4

1Instituto de Geofisica, Universidad Nacional Autónoma de México, Coyoacán 04510, Mexico City, Mexico
2Earth Sciences and Engineering, Imperial College London, SW7 2AZ, United Kingdom

3Natural History Museum, Humboldt University, D-10099, Berlin, Germany
4Department of Geology, Vrije Universiteit Brussel, Pleinaan 2, B-1050, Brussels, Belgium

In the June and July issues of Meteoritics & Planetary
Science, we present the initial results of the Chicxulub
Scientific Drilling Project (CSDP).

The Chicxulub crater is a unique impact structure
associated with one of the most dramatic geological events in
the Phanerozoic. It is buried beneath carbonate sediments in
the northern Yucatán Peninsula, southeastern Mexico. It has a
diameter of 180–200 km and a complex multi-ring structure
(Fig. 1). It represents the youngest and the best preserved of
only three large multi-ring impact basins documented in
terrestrial geological record. The impact that excavated the
Chicxulub crater has been dated at 65 Ma and, therefore, is
related to the event that marks the Cretaceous/Tertiary (K/T)
boundary and the extinction of about 75% of species (50% of
genera, including the dinosaurs) (Alvarez et al. 1980;
Hildebrand et al. 1991). This crater presents a unique
opportunity to discover new important information on the
formation and characteristics of such large multi-ring impact
craters, their environmental and climatic effects, and their
implications for geological and biological evolution.

The Chicxulub crater has been the focus of numerous
studies, particularly in the last decade. Studies include
offshore and onshore geophysical surveys, drilling/coring,
laboratory analyses of impact breccias and melt, and
computer modeling (e.g., Sharpton et al. 1992; Morgan et al.
1997, 2000; Collins et al. 2002; Ebbing et al. 2001).  Drilling
inside the structure and in its immediate vicinity has been
carried out within the oil exploratory program by PEMEX
with intermittent core recovery and, more recently, by the
National University of Mexico (UNAM) Chicxulub drilling
program resulting in continuous core recovery.

The need for drilling/coring within the deeper part of the
impact basin, where the crater floor is buried under several
hundred meters of Tertiary carbonate sediments, was
recognized already during the early studies of the crater
because only the uppermost crater-related deposits were
drilled (Urrutia-Fucugauchi et al. 1996; Rebolledo-Vieyra et
al. 2000). With the initiation of the International Continental
Scientific Drilling Program (ICDP), interest in drilling the
crater increased and CSDP was developed as part of an
international collaboration within the framework of ICDP.

The drilling project was financed by ICDP and the
National University of Mexico (UNAM) and was coordinated
by UNAM. The CSDP borehole Yaxcopoil-1 was drilled from
December 2001 through March 2002 in the southern sector of
the crater at ~62 km radial distance from the approximate
crater center at Chicxulub Puerto (Fig. 1). The Yaxcopoil-1
(Yax-1) borehole was planned to core continuously into the
lower part of the post-impact carbonate sequence, the impact
breccias, and the displaced Cretaceous rocks. The drill site at
Hacienda Yaxcopoil (Figs. 2a and 2b) was selected based on
integration of gravity, magnetics, magnetotelluric and
offshore seismic surveys, pre-existing boreholes of PEMEX
and UNAM programs, site conditions and access, land
ownership, water availability, and an environmental impact
assessment (Urrutia-Fucugauchi et al. 2001). 

An INDECO rotary drill rig from Perforaciones
Industriales Termicas, S. A. (PITSA) and the coring device
from the Drilling, Observation, and Sampling of the Earth’s
Continental Crust (DOSECC) were used for the drilling/
coring operations. Rotary mode was used to drill from the
surface to the depth of 404 m. After running wireline logs and
casing the borehole, drilling was continued with wireline
coring of the carbonate sequence and impact lithologies.
Cores 63.5 mm in diameter were obtained to the depth of
993 m. At this depth, the HQ coring string became stuck and
eventually was left in the hole as casing. Coring resumed with
an NQ string (core diameter of 47.6 mm) to the final depth of
1511 m. 

Geophysical logging was conducted after completion of
drilling through the first 400 m and reaching the final depth of
1511 m. Observations included hole deviation and azimuth
(caliper, SP), magnetic susceptibility, radioactive element
contents, gamma ray, electrical resisitivity, temperature, and
conventional and waveform sonic. The Yax-1 borehole is
open and available for experiments under a ten-year
agreement between the Yaxcopoil Hacienda and UNAM.
Several geophysical logging campaigns have been conducted
after completion of the drilling project.

A core laboratory and temporary repository was
established at the University of Yucatán in Mérida. Facilities
for digital photography of core boxes and core segments and

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788 J. Urrutia-Fucugauchi et al.

an automated digital core scanner were available for
documentation. Cores were transported from the drill site
daily, and information was made available on the CSDP web
site through the ICDP information system. After completion
of drilling operations, cores were packed and shipped to the
UNAM Core Repository in Mexico City. Cores were further
examined and then cut longitudinally in halves (one half is the
project archive, while the other one is available for sampling

by CSDP science team). Full cores and halves were digitally
scanned for high resolution images, some of which are
presented in the papers included in these two volumes of
MAPS.

The CSDP recovered core from the lower Tertiary
carbonate sequence, impact breccias, and overlying
Cretaceous carbonates, down to the depth of 1511 m. Core
recovery was 98.5%. The Tertiary carbonates were cored
between 404 m and 795 m. Impact breccias were cored
between 795 m and 895 m, presenting an unexpectedly thin
sequence of impactites, given the greater thickness of such
breccias in wells located toward and outward the crater center
relative to Yax-1. Beneath the impact breccias, a sequence of
carbonate rocks (limestones, dolomites, and anhydrite) were
recovered. The dip of the carbonates varies from being sub-
horizontal to up to 60 degrees, and these rocks contain thin
dikes of breccia and melt. Impact breccias have been divided
into six units which, from top to bottom, are (prelimary log
names): redeposited suevites (794.63–808.02 m), suevites
(808.02–822.86 m), chocolate-brown melt breccias (822.86–
845.80 m), glass-rich variegated suevites (845.80–861.06 m),
green monomicitic-autogene melt breccias (861.06–
884.92 m), variegated polymicitic, allogenic clast melt
breccias (884.92–894.94 m) (Dressler et al. 2003). A similar
subdivision with a different classification of the lithologies

Fig. 1. Location of the CSDP borehole Yax-1.

Fig. 2a. Drilling operations at Hacienda Yaxcopoil.



CSDP-Introduction 789

has been proposed in Dressler et al. (2003) and in other papers
included in these volumes (e.g., Tuchscherer et al. 2004;
Stöffler et al. 2004). The Cretaceous sedimentary rocks below
about 895 m are cut with dikes of polymict breccias and
display zones of monomict brecciation. They appear to
represent “megablocks” displaced by the impact event.
Anhydrite layers, the thickness of which varies from a few
centimeters to up to 15 m, and make some 27% of the
megablocks. Organic-rich layers and oil-bearing units are
present at depths between 1410 and 1455 m (according to
Kenkmann et al. [2004], this layer starts at 1263 m.).

Scientific study of Yax-1 core samples and
complementary studies are allowing researchers to: 1)
evaluate the link between the Chicxulub crater and global K/
T boundary layer and mass extinction; 2) study large-scale
cratering processes; 3) investigate post-impact crater
modifications, environmental evolution, and faunal recovery;
and 4) provide additional constraints on target compositions
and deformation styles characteristic of the zone flanking the
collapsed transient cavity.

Initial studies have already provided important progress
on these issues and, at the same time, left questions
unanswered and opened new lines of inquiry. For instance: 

1. The proportion of basement material within the impact
breccias is higher than observed at other craters, opening
exciting possibilities for investigations of excavation
models and the nature of the Yucatán crust. 

2. The impact breccia layers are thinner than predicted,
with implications for crater structure, breccia
emplacement, and crater formation. 

3. Although there are layers of anhydrite in the target rocks,
there is a surprising lack of evidence for anhydrite in the
impact breccias. 

4. Several different analyses document the importance of
post-impact hydrothermal alteration within the core
samples.

5. Recovered blocks of Cretaceous and impactites provide
valuable material for laboratory analyses, despite the
effects of subsequent alteration.  

6. The origin of the thick carbonate sequence beneath the
breccias (>600 m) has provoked an interesting debate
and requires further study. 

7. Initial studies of the impactite and early Paleocene
stratigraphy have provided interesting age constraints
and information on sequence completeness (for example
the identification of the 29r/29n chron boundary just
above the appearance of the first Danian fossils),
provoking a debate about the age of the Chicxulub
impact.
In two consecutive volumes of MAPS, we present the

initial results of the CSDP Science Team. These volumes
include papers on the petrology, mineralogy, geochemistry,
hydrothermal alteration, and degree of shock of the impactites,
as well as interpretations of their deposition, including

Fig. 2b. The CSDP rig at Hacienda Yaxcopoil.



790 J. Urrutia-Fucugauchi et al.

numerical modeling. Papers on the late Cretaceous section
include studies of their stratigraphy, sedimentology, structure
and deformation, and cross-cutting dikes, as well as
interpretations of their origin. Other contributions include
physical property measurements on the core, seismic-, bio- and
magneto-stratigraphic studies, and evidence for the existence
of a hydrothermal plume in the early Tertiary ocean.

The guest editors would like to acknowledge the valuable
contribution of the reviewers of the papers submitted for the
special volumes. Our thanks to: D. Ames, K. Benn, R. J.
Bodnar, T. Bralower, R. Buffler, O. Campos-Enriquez, A.
Deutsch, H. Dypvik, S. D’Hondt, A. Goguitchaichvili, S.
Gulick, M. Harting, L. Hecht, A. Hildebrand, F. Hörz, B.
Huber, G. Keller, T. Kenkmann, D. Kent, K. Kirsimae, C.
Koeberl, D. Kring, F. Kyte, V. Luciani, B. Milkereit, A.
Montanari, O. Morton, H. R. Newsom, R. Norris, J. Ormo, H.
Palme, L. Pesonen, K. Pope, W. U. Reimold, E. Robin, P.
Rochette, J. Safanda, J. Smit, A. M. Soler, R. Stoessel, D.
Stüben, R. Tagle, D. H. Tarling, A. Therriault, D. Thomas, L.
Thompson, F. Tsikalas, R. Walker, J. Whitehead, L. Zurcher. 

We also tkank the Editor, Tim Jull, and the editorial staff
of Meteoritics & Planetary Science. Their professional
assistance and patience have made this effort possible. 

Acknowledgments–The CSDP is an international cooperation
research project. The support received from numerous
individuals and institutions is gratefully acknowledged. We
are thankful for the support and encouragement of ICDP
Chairman Prof. Rolf Emmermann. ICDP, UNAM,
CONACYT, Government of Yucatán, Hacienda Yaxcopoil,
Universidad Autónoma de Yucatán, and PEMEX have
provided financial and/or logistic support. 

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