The Chesapeake Bay Crater: Geology and Geophysics of a Late Eocene Submarine Impact Structure

528 Pages·2004·24.531 MB·English

by  Dr. C. Wylie Poag, Dr. Christian Koeberl, Dr. Wolf Uwe Reimold (auth.)

Impact Studies
Series Editor: Christian Koeberl
Editorial Board
Eric Buffetaut ( CNRS, Paris, France)
lain Gilmour (Open University, Milton Keynes, UK)
Boris Ivanov (Russian Academy of Sciences, Moscow, Russia)
Wolf Uwe Reimold (University of the Witwatersrand, Johannesburg, South Africa)
Virgil L. Sharpton (University of Alaska, Fairbanks, USA)
Springer-Verlag Berlin Heidelberg GmbH
C. Wylie Poag
Christian Koeberl
Wolf Uwe Reimold
The Chesapeake
Bay Crater
Geology and Geophysics of a Late Eocene
Submarine Impact Structure
EXIRA
MATERIALS
With 207 Figures, 42 Tables extras.springer.com
Springer
c.
DR. WYLIE POAG DR. CHRISTIAN KOEBERL
U.S. Geological Survey Department of Geological
384 Woods Hole Road Sciences
Woods Hole, MA 02543-1598 University of Vienna
USA Althanstrasse 14
Email: [email protected] 1090 Vienna
Austria
DR. WoLF UwE REIMOLD Email:
School of Geosciences [email protected]
University of the Witwatersrand
P.O. Wits 2050
Johannesburg, South Africa
Email: reimoldw@geosciences. wits.ac.za
Additional material to this book can bc downloadcd from http://cxtras.springer.com.
ISBN 978-3-642-62347-9 ISBN 978-3-642-18900-5 (eBook)
DOI 10.1007/978-3-642-18900-5
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© Springer-Verlag Berlin Heidelberg 2004
Originally published by Springer-Verlag Berlin Heidelberg New York in 2004
Softcover reprint of the hardcover 1s t edition 2004
The use of general descriptive names, registered names, trademarks, etc. in this publication does not
imply, even in the absence of a specific statement, that such names are exempt from the relevant protective
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Cover Design: Kirchner, Heidelberg
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Printed on acid free paper 32/2132 AO - 5 4 3 2 1 o
We dedicate this book to David J. Roddy (1932-2002), one of the pioneers of im
pact cratering studies. For 40 years, Dave was a driving force in the analysis of
natural hypervelocity impact structures and the mechanics of nuclear explosion
cratering. The wealth of data and observations he contributed remains fundamen
tal to our understanding of the physics of impact cratering and the shock-wave de
formation of the Earth's crustal materials.
Preface
" ... bangs have replaced whimpers and the geological record has become much
more exciting than it was thought to be." Derek Ager (1993) The New Catastro
phism. Cambridge University Press, Cambridge, p xix
Scientific and public interest in asteroids, comets, and meteorite impacts has never
been more intense than right now. Much of this interest stems from the fervent
debates surrounding the causes of the Cretaceous-Tertiary mass extinctions and
their possible relationships to a giant bolide impact in Mexico's Yucatan Penin
sula. Recent spectacular impacts on Jupiter, and several near misses of our own
planet by Near-Earth Objects have intensified professional and popular discussion
of society's imperative need to understand the process and effects of bolide im
pacts. In the United States, the scientific community and the public, as well, were
startled to learn, in 1994, that the largest impact structure in this country had been
detected beneath Virginia's portion of the Chesapeake Bay. Seismic surveys and
deep coring revealed a huge crater, 85 kilometers in diameter and more than a
kilometer deep, stretching from Yorktown, Virginia, to 15 kilometers out onto the
shallow continental shelf. Several of Virginia's major population centers, includ
ing Norfolk, Hampton, and Newport News, are located on the western rim of the
crater, and still experience residual effects of the original collision, 36 million
years after the impact took place.
Exploration and documentation of the Chesapeake Bay impact structure has
proceeded in three phases. Phase one was characterized by mainly serendipitous
discoveries. Initial clues to its presence came from deep-sea cores collected by
scientists aboard the drillship Glomar Challenger, during a coring cruise off the
coast of Atlantic City, New Jersey, in 1983. Diagnostic evidence of an impact, in
the form of microtektites and impact-shocked minerals, showed up in a few cen
timeters of late Eocene chalk, dated at ~35 million years old. The thickness and
coarse-grained nature of the impact debris indicated that the impact site must have
been relatively close to the core site. Three years later (1986), the first of four
stratigraphic coreholes in southeastern Virginia recovered additional impact
generated debris, containing diagnostic shock-metamorphosed minerals. The geo
logic age of the debris was identical to the microtektite-bearing debris cored off
New Jersey. In 1994, acquisition of multichannel seismic reflection data from
commercial oil companies revealed that two of the Virginia coreholes had pene
trated the massive body of impact breccia that fills an enormous impact crater bur
ied beneath Chesapeake Bay. Each of these three milestone events was the result
VIII Preface
of chance - surprise discoveries made during geologic investigations of unrelated
phenomena.
Phase two of the crater documentation was marked by the acquisition of addi
tional seismic reflection data to clarify the detailed structure and morphology of
the impact structure. When added to the previous data set, the new surveys
yielded a database of >2000 kilometers of seismic reflection profiles. These seis
mic data clearly revealed that the Chesapeake Bay structure is a complex, peak
ring/central-peak structure, with many features similar to those of other large ter
restrial and planetary impact structures, but which displays several unique aspects,
as well.
Firm knowledge of the crater's structure and morphology allowed the third
phase of exploration to begin in 2000. Phase three emphasized the careful selec
tion of new core sites to answer specific questions regarding impact processes and
resultant impact-generated deposits.
Now, 20 years after the New Jersey core discoveries, researchers have estab
lished the principal structural, morphological, depositional, and paleoenvironmen
tal features of the Chesapeake Bay impact and its resultant structure. This volume
contains the first synthesis of our current knowledge of this fascinating cosmic
event and its aftermath. It is our hope that the broad spectrum of data and inter
pretations we offer herein will enhance the understanding and appreciation of bo
lide impacts as crucial events in the geologic and biologic evolution of our planet.
C. Wylie Poag Christian Koeberl W. Uwe Reimold
US Geological Survey University of Vienna University of the
Woods Hole, Vienna, Austria Witwatersrand
Massachussetts, USA Johannesburg, South
Africa
Acknowledgments
We are indebted to a host of colleagues who contributed data, analyses, interpreta
tions, and advice, during our roughly 12-year study of the Chesapeake Bay impact
crater. The list is headed by Debbie Hutchinson, Steve Colman, Tommy O'Brien,
Barry Irwin, Dave Nichols, Jeremy Loss, John Evans, and Nancy Soderberg, who
constituted the shipboard science party that collected seismic reflection data
aboard the RIV Seaward Explorer (1996). Texaco, Inc. (particularly Parish Erwin)
contributed the multichannel seismic reflection profiles that originally defined the
major features of the crater. Rusty Tirey, John Grow, and Pete Popenoe collected
the early USGS seismic reflection data before we knew the crater was there. Dave
Foster and John Diebold helped to acquire and process the seismic data collected
by the RIV Maurice Ewing (1998). Dave Powars, Bob Mixon, Scott Bruce, and
Don Queen carried out the initial coring programs that provided ground truth for
the seismic reflection analyses. Marie-Pierre Aubry provided critical analyses of
calcareous nannofossils. Gene Shoemaker, Jens Ormo, Filippos Tsikalas, Henning
Dypvik, Richard Grieve, Peter Schultz, Kevin Pope, Bill Glass, Ron Stanton, Jeff
Williams, Dave Folger, Glen Izett, and Michael Rampino provided expert advice
and much needed encouragement during this project. Tom Aldrich, Joe Newell,
and the crews of the RIV Seaward Explorer and RIV Maurice Ewing facilitated
collection of seismic data in Chesapeake Bay. John Costain, Carl Bowin, Larry
Poppe, Warren Agena, Myung Lee, Dann Blackwood, Dick Norris, Ed Mankinen,
Judy Commeau, Louie Kerr, and Jeff Plescia provided critical data, data analysis
or processing, scientific advice, and technical assistance. Chuck Pillmore pro
vided the Manson seismic profile; Lubomir Jansa provided the Montagnais seis
mic line. The Deep Sea Drilling Project (DSDP) and Ocean Drilling Program
(ODP) provided offshore cores. The National Geographic Research Committee
provided funding to the senior author for the single-channel survey of the crater.
Steve Curtin provided downhole logs. Core drilling in the Chesapeake Bay im
pact crater has been a cooperative effort among the Hampton Roads Planning Dis
trict Commission, the NASA Langley Research Center, the Virginia Department
of Environmental Quality, the Geology Department of the College of William and
Mary, and the USGS. The Chesapeake Coring Team (Greg Gohn, Dave Powars,
Scott Bruce, Laurel Bybell, Tom Cronin, Lucy Edwards, Norm Frederiksen,
Wright Horton, Glen Izett, Gerry Johnson, Joel Levine, Randy McFarland, Jim
Quick, Steve Schindler, Jean Self-Trail, Matt Smith, Bob Stamm, Rob Weems,
Art Clark, and Don Queen) acquired and described the NASA Langley, North, and
Bayside cores. Becca Drury, Michael Taylor, Andy Mcintire, Laura Hayes, Philip
Moizer, Emily Denham, Daniel Boamah and Kassa Amare provided computer
skills and laboratory assistance. Philip Moizer also collected a new set of gravity
X Acknowledgments
data on the Delmarva Peninsula and carried out the gravity modeling of the crater.
VeeAnn Cross constructed the 3-D structural model of the crater.
We are especially indebted to the reviewers, David Crawford, Henning Dypvik,
David Foster, Jens Ormo, Larry Poppe, Scott Snyder, Filippos Tsikalas, and Buck
Ward, for significant improvements to the manuscript.
The USGS Coastal and Marine Geology Program and Earth Surface Processes
Program supported Poag's crater research. Koeberl's geochemical and petro
graphic studies were supported by the Austrian Science Foundation (FWF) project
Y58-GEO. Reimold's research was supported by the National Research Founda
tion of South Africa and a grant from the University of the Witwatersrand to the
Impact Cratering Research Group. This is ICRG Contribution No. 45.
Contents
1 Introduction ......................................................................................................... l
2 Geological Framework of Impact Site .............................................................. 41
2.1 Crystalline Basement Rocks ........................................................................ 41
2.1.1 Regional Tectonostratigraphy ................................................................ 41
2.1.2 Crystalline Basement Rocks in Boreholes ............................................ .43
2.1.3 Regional Configuration of Crystalline Basement Surface .................... ..45
2.2 Coastal Plain Sedimentary Rocks ................................................................ 47
2.2.1 General Stratigraphic Framework ..........................................................4 7
2.2.2 Preimpact Deposits ............................................................................... .48
2.2.2.1 Potomac Formation ......................................................................... .48
2.2.2.2 Unnamed Upper Cretaceous Beds ................................................... 50
2.2.2.3 Brightseat Formation ....................................................................... 50
2.2.2.4 Aquia Formation .............................................................................. 50
2.2.2.5 Marlboro Clay ................................................................................. .50
2.2.2.6 Nanjemoy Formation ....................................................................... 51
2.2.2.7 Piney Point Formation ..................................................................... 51
2.2.2.8 Unnamed Upper Eocene Deposits ................................................... 51
2.2.3 Postimpact Deposits .............................................................................. 51
2.2.3 .1 Chickahominy Formation ................................................................ 52
2.2.3.2 Delmarva Beds ................................................................................ 52
2.2.3.3 Old Church Formation ..................................................................... 52
2.2.3.4 Calvert Formation ............................................................................ 54
2.2.3.5 Choptank Formation ........................................................................ 54
2.2.3.6 St. Marys Formation ........................................................................ 54
2.2.3.7 Eastover Formation .......................................................................... 54
2.2.3 .8 Yorktown Formation ....................................................................... .54
2.2.3.9 Chowan River Formation ................................................................ .55
2.2.3 .1 0 Quaternary Formations .................................................................. 55
2.3 Sequence Stratigraphy ................................................................................. 57
2.4 Paleogeography of Impact Site .................................................................... 57
2.5 Subsidence of Virginia Continental Margin ................................................ 64
2.6 Initial Evidence of East Coast Impact.. ........................................................6 4
2.7 Onshore Borehole Evidence ........................................................................ 69
2.7.1 Noncored Boreholes .............................................................................. 69
2.7.2 Cored Boreholes .................................................................................... 69