Backbone of the Americas: Shallow Subduction, Plateau Uplift, and Ridge and Terrane Collision (Geological Society of America Memoir 204)

284 Pages·2009·23.37 MB·English

by  Suzanne Mahlburg Kay

Backbone of the Americas:
Shallow Subduction, Plateau Uplift, and
Ridge and Terrane Collision
edited by
Suzanne Mahlburg Kay
Department of Earth and Atmospheric Sciences
Snee Hall
Cornell University
Ithaca, New York 14853
USA
Víctor A. Ramos
Laboratorio de Tectónica Andina
Facultad de Ciencias Exactas y Naturales
Universidad de Buenos Aires–
Consejo Nacional de Investigaciones Científicas y Técnicas
Ciudad Universitaria Pabellón 2
Buenos Aires
Argentina
William R. Dickinson
Department of Geosciences
University of Arizona
Tucson, Arizona 85721
USA
Memoir 204
3300 Penrose Place, P.O. Box 9140 Boulder, Colorado 80301-9140, USA
2009
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Library of Congress Cataloging-in-Publication Data
Backbone of the Americas : shallow subduction, plateau uplift, and ridge and terrane collision /
edited by Suzanne Mahlburg Kay, Víctor A. Ramos, William R. Dickinson.
p. cm. — (Memoir ; 204)
Includes bibliographical references.
ISBN 978-0-8137-1204-8 (cloth)
1. Orogeny—America. 2. Geology, Structural—America. I. Kay, Suzanne Mahlburg, 1947–. II.
Ramos, Víctor A. III. Dickinson, William R.
QE621.5.A45B33 2009
551.8′2091812—dc22
2009009035
Cover: SRTM (Satellite Radar Topographic Mission) image showing the central and southern part
of the Central Andean Puna-Altiplano Plateau. From left to right are the Pacific Ocean, the forearc
valleys and ranges, the high plateau (white and gray tones) with high volcanic peaks and giant
ignimbrite calderas (largely red and purple tones), and the foreland thrust belts (green and brown
tones). See Chapter 11 (“Shallowing and steepening subduction zones, continental lithospheric loss,
magmatism, and crustal flow under the Central Andean Altiplano-Puna Plateau”) for discussion of
these features.
This SRTM image was processed by Jay Hart of Trumansburg, New York. Elevation data were
compiled into a single graphic from Costa Rica to the Falklands, with shadows thrown from the east
and a palette designed to isolate local variation. This excerpt from Cordillera is used with permission
from Hart (http://www.earthpattern.com).
10 9 8 7 6 5 4 3 2 1
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .v
1. Anatomy and global context of the North American Cordillera . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
William R. Dickinson
2. Anatomy and global context of the Andes: Main geologic features and the Andean
orogenic cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Víctor A. Ramos
3. Neogene collision and deformation of convergent margins along the backbone
of the Americas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
R. von Huene and C.R. Ranero
4. Relation of flat subduction to magmatism and deformation in the western United States . . . . . .85
Eugene Humphreys
5. Structural geologic evolution of the Colorado Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
George H. Davis and Alex P. Bump
6. Three-dimensional kinematics of Laramide, basement-involved Rocky Mountain
deformation, USA: Insights from minor faults and GIS-enhanced structure maps . . . . . . . . . .125
Eric A. Erslev and Nicole V. Koenig
7. Cretaceous–Eocene magmatism and Laramide deformation in southwestern Mexico:
No role for terrane accretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
Michelangelo Martini, Luca Ferrari, Margarita López-Martínez, Mariano Cerca-Martínez,
Víctor A. Valencia, and Lina Serrano-Durán
8. Geochemical evolution of igneous rocks and changing magma sources during the formation
and closure of the Central American land bridge of Panama . . . . . . . . . . . . . . . . . . . . . . . . . . .183
Gerhard Wörner, Russell S. Harmon, and Wencke Wegner
9. Mode and timing of terrane accretion in the forearc of the Andes in Ecuador . . . . . . . . . . . . . .197
Cristian Vallejo, Wilfried Winkler, Richard A. Spikings, Leonard Luzieux, Friedrich Heller, and
François Bussy
10. Influence of the subduction of the Carnegie volcanic ridge on Ecuadorian geology:
Reality and fiction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .217
François Michaud, Cesar Witt, and Jean-Yves Royer
iii
iv Contents
11. Shallowing and steepening subduction zones, continental lithospheric loss, magmatism,
and crustal flow under the Central Andean Altiplano-Puna Plateau . . . . . . . . . . . . . . . . . . . . . .229
Suzanne Mahlburg Kay and Beatriz L. Coira
12. Flat-slab subduction and crustal models for the seismically active Sierras Pampeanas
region of Argentina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .261
Patricia Alvarado, Mario Pardo, Hersh Gilbert, Silvia Miranda, Megan Anderson, Mauro Saez,
and Susan Beck
Preface
This volume has its genesis in the “Backbone of the Americas: Patagonia to Alaska” conference that
took place in the city of Mendoza, Argentina, from 2 to 7 April 2006. The conference was convened by the
Asociación Geológica Argentina and the Geological Society of America in collaboration with the Socie-
dad Geológica de Chile and was the fi rst meeting on this scale to be jointly convened by North and South
American geologic societies. Some 400 participants from 20 countries along the western margins of the
Americas and elsewhere participated. The purpose of the meeting was to explore common scientifi c themes
affecting the evolution of the Cordilleras of the Americas from a multidisciplinary international perspective.
Major themes included collision of active and aseismic oceanic ridges, shallowing and steepening subduc-
tion zones, plateau and orogenic uplift, and terrane collision. This volume presents a selection of papers by
the invited plenary speakers and other represenative presentations of the symposium.
The volume begins with overview papers on the Precambrian to Holocene evolution of the North, Cen-
tral, and South American Cordilleras and a review of marine tectonic processes along the margin. These are
followed by a series of papers highlighting distinctive processes and tectonic regions along the margin. The
discussions begin in North America, proceed through Central America, and progress into South America.
The presentations here are complemented by overviews in fi ve fi eld trip guides prepared in conjunction with
the meeting to highlight the meeting themes in South America. These guides appear in a separate volume
edited by Kay and Ramos, which is entitled Field Trip Guides to the Backbone of the Americas in the South-
ern and Central Andes: Ridge Collision, Shallow Subduction, and Plateau Uplift. The volume was published
in 2008 as FLD013 in the Geological Society of America Field Guide series.
The fi rst chapter here, by William R. Dickinson (University of Arizona), sets the stage in North America
by presenting an overview of the evolution, setting, and global context of the 5000-km-long North American
orogen. Unlike the Central and South American and Alaskan cordilleras, much of the margin of the North
American cordillera is currently characterized by dextral transform faults. The history of this margin initi-
ated with the breakup of the Rodinian supercontinent, which created a Neoproterozoic to early Paleozoic
passive margin that was later modifi ed by Permian-Triassic transform faults from California into Mexico,
late Paleozoic to Mesozoic accretion of oceanic island arcs and subduction complexes, and subduction after
the Triassic. Mesozoic to Cenozoic terrane accretion occurred as far south as northern South America, and
subduction produced retroarc basins and Mesozoic to Cenozoic batholiths. The subduction era largely ended
with the shallow subduction episode that produced the Laramide breakup of the Cordilleran foreland. The
history ends with extension in the Basin and Range, and margin-parallel dextral strike slip that displaced
elongate segments of the coastal region to the north.
The second chapter, by Víctor A. Ramos (Universidad de Buenos Aires, Argentina), presents a comple-
mentary overview of the evolution of the western South American margin, which is the longest continen-
tal margin currently dominated by subduction. The review shows that subduction began shortly after the
Late Proterozoic breakup of the Rodinia supercontinent with terrane amalgamation occurring throughout
the Neoproterozoic and Paleozoic all along the margin. Episodes of rifting, detachment, and re-accretion
led to a complex system of exotic to para-autochthonous Neoproterozoic and Paleozoic terranes in the Cen-
tral Andes. Generalized rifting associated with the Mesozoic breakup of the Pangean supercontinent and
opening of the South Atlantic Ocean followed this period. The subsequent northeastward absolute motion
of Gondwana created negative trench rollback leading to a subduction regime characterized by backarc
v
vi Preface
extension that lasted until the late Early Cretaceous. The Early Cretaceous to middle Miocene history in the
north is distinctive in that island-arc and oceanic plateau collisions along the Venezuelan to Ecuadorian mar-
gin occurred in association with Caribbean plate motion. The Cenozoic is marked by episodes of shallowing
and steepening of the subducting plate leading to repeated broadening and narrowing of the volcanic arc
interspersed with times of magmatic quiescence, development of foreland fold-thrust systems, and intermit-
tent delamination of continental lithosphere and crust.
The third chapter, by Roland Von Huene (U.S. Geological Survey, University of California–Davis) and
Cesar Ranero (Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain), highlights Neogene col-
lision and deformation along the eastern Pacifi c convergent margin. All along the margin, features with high-
standing relief on the subducting oceanic plate are shown to be colliding with continental slopes. Common
processes include the uplift of the continental margin, accelerated seafl oor and basal subduction-erosion,
and shallow subduction zones. At a smaller scale, the subduction of seamounts and lesser ridges attached to
the subducted plate produce temporary surface uplift. The collision and subduction of the Yakutat terrane in
North America, the Cocos Ridge in Central America, the Nazca and Juan Férnandez Ridges in central South
America, and the south Chile triple junction in southern South America are considered.
The fourth chapter, by Eugene Humphreys (University of Oregon), discusses the relation of fl at subduc-
tion to magmatism and deformation in the western United States from a geophysical point of view. Hum-
phreys argues that fl at subduction of the Farallon plate during the Laramide orogeny was due to a combina-
tion of subduction of an oceanic plateau and suction in the mantle wedge as the shallowing slab approached
the North American cratonic root. The shallow slab caused the lithosphere to dehydrate, and removal of the
fl at slab put the asthenosphere in contact with the basal lithosphere, leading to magmatism that was particu-
larly intense where the basal lithosphere was fertile, below the present Basin and Range Province. Heating
of the weakened lithosphere in that region led to convective instability. The strongest part of the lithosphere
remained a plateau, and the weak park to the west collapsed to form the Basin and Range. The development
of a transform plate boundary on the western margin led to the weakened westernmost zone being entrained
within the Pacifi c plate.
The fi fth chapter, by George Davis (University of Arizona) and Alex Bump (BP Exploration and Pro-
duction Technology, Houston), analyzes the tectono-structural evolution of the Colorado Plateau. These
authors point to the role of the Neoproterozoic, Paleozoic, and Mesozoic sedimentary rocks and the hetero-
geneous latest Paleoproterozoic and Mesoproterozoic crystalline basement, which they mechanically overlie
in producing the dominant Late Cretaceous to early Tertiary Laramide basement-cored uplifts and associ-
ated monoclines. They argue that the geometries of these uplifts refl ect “trishear” fault-propagation, that
the uplifts largely formed as a response to tectonic inversion of Neoproterozoic normal-displacement shear
zones, and that the principal NE-SW– and NW-SE–directed compressive stresses generating the uplifts were
transmitted through the basement in response to plate-generated stresses. The deformation is attributed to
the Colorado Plateau being caught in a bi-directional tectonic vise with the northwest side subjected to SE-
directed compressive stress, and the base of the lithosphere subjected to viscous NE-directed undershearing
produced by the shallowly subducting Farallon slab. The plateau is argued to have systematically deformed
along the weakest deep basement links with variable reactivation of old shear zones leading to a disparate
array of uplifts.
The sixth chapter, by Eric Erslev and Nicole Koenig (Colorado State University), focuses on the three-
dimensional kinematics of Laramide Rocky Mountain deformation with an emphasis on contractional, base-
ment-involved foreland deformation. Their perspective comes from the analyses of minor faults and geo-
graphic information system (GIS)–enhanced structural maps. They discuss current kinematic hypotheses for
the Laramide orogeny, which include single-stage NE- to E-directed shortening, sequential multidirectional
shortening, and transpressive deformation partitioned between NW-striking thrust and N-striking strike-slip
faults. Proposed driving forces range from external stresses paralleling plate convergence to internal stresses
related to gravitational collapse of the Cordilleran thrust belt. Laramide deformation is argued to show a pri-
mary external infl uence of ENE-directed shortening parallel to North American–Farallon plate convergence
parameters, complexities related to localized preexisting weaknesses, and impingement by the adjoining
Cordilleran thrust belt. Obliquities between convergence directions and the northern and southeastern bound-
aries of the Laramide province are argued to have created transpressive arrays of en echelon folds and arches
without major through-going strike-slip faults.
Preface vii
The seventh chapter, by Michelangelo Martini (Universidad Nacional Autónoma de México [UNAM],
Querétaro, Mexico), Luca Ferrari (UNAM, Querétaro), Margarita López-Martínez (Ensenada, Mexico),
Mariano Cerca-Martínez (UNAM, Querétaro), Victor Valencia (University of Arizona), and Lina Serrano-
Durán (UNAM, Querétaro), focuses on the causes of Cretaceous to Eocene magmatism and Laramide defor-
mation in southwestern Mexico. They use new mapping and structural studies along with new 40Ar/39Ar and
U-Pb zircon dates from a broad region in the central-eastern part of the widely discussed Guerrero terrane to
argue against models that attribute the Laramide-age deformation in this region to accretion of allochthonous
terranes. They favor a model in which most of the Guerrero terrane is composed of autochthonous or parau-
tochthonous units that formed on the thinned continental margin of the North American plate, and in which
the Mesozoic magmatic and sedimentary rocks record a long-lasting migrating, west-facing arc and related
extensional backarc and forearc basins. The driving force to generate the Late Cretaceous–early Tertiary
shortening and shearing of the southern margin of the North American plate remains poorly understood.
In the eighth chapter, Gerhard Wörner (Universität Göttingen, Germany), Russell Harmon (U.S. Army
Research Laboratory), and Wencke Wegner (Universität Göttingen) use magmatic rocks from the, until
recently, poorly studied Cordillera de Panama to put the evolution and closure of the Central American land
bridge into a tectonic framework. They argue that the Isthmus of Panama refl ects intermittent magmatism
and oceanic plate interactions over the last 100 m.y., and they trace its early evolution using the chemistry of
the magmatic rocks in the Caribbean large igneous province. Evidence for the initiation of arc activity comes
from the 66–45 Ma Chagres igneous complex, which could constitute much of the upper crust in the region.
The chemistry of this complex shows that by 66 Ma, the mantle under the region was more depleted and
variable in composition than the Galapagos hotspot mantle that gave rise to older magmas. The chemistry
of the subsequent 20–5 Ma andesites shows that any plume infl uence was gone by the Miocene. The end of
this arc stage at about 5 Ma coincided with the collision of a series of aseismic ridges. The chemistry of the
younger lavas (<2 Ma) is argued to refl ect the melting of an oceanic ridge subsequent to collision rather than
the competing hypothesis, which states that their chemistry refl ects addition of continental lithosphere into
the mantle through forearc subduction-erosion.
Moving into northern South America, the ninth chapter, by Cristian Vallejo (ETH [Eidgenössische Tech-
nische Hochschule], Zürich), Wilfried Winkler (ETH Zürich), Richard A. Spikings (University of Geneva),
Leonard Luzieux, (ETH Zürich), Friedrich Heller (ETH Zürich), and François Bussy (Université de Lau-
sanne, Switzerland), presents an updated analysis on the mode and timing of the collision of oceanic terranes
against the continental margin of Ecuador. This paper presents new fi eld data on the volcanic rocks of the
Western Cordillera, new paleomagnetic constraints, and a new stratigraphic framework for oceanic plateau
postcollisional volcanic rocks based on an extensive set of new U-Pb and 40Ar-39Ar geochronologic ages.
The authors propose a new model for the geodynamic evolution of the accreted terranes and the subduction
geometry of the colliding plateau in the latest Cretaceous.
The tenth chapter, by François Michaud (Nice, France), Cesar Witt (Escuela Politécnica, Ecuador), and
Jean-Yves Royer (Brest, France), deals with fact and fi ction over the infl uence of the subduction of the Car-
negie volcanic ridge on Ecuadorian geology, particularly with respect to the timing of the initiation of ridge
subduction and processes associated with collision against the continental margin. They conclude that there
is no clear link between deformation along the continental margin and coastal uplift with the subduction of
the Carnegie Ridge. They further argue for relatively recent initiation of ridge subduction based on seismic
evidence against a shallowly subducting slab beneath Ecuador, alternatives to partial melting of the subduct-
ing ridge to explain the adakitic signatures in magmatic rocks, and insignifi cant vertical uplift related to ridge
subduction. Finally, they use global positioning system (GPS) results to argue that the northward migration
of the North Andean block can explain inhibition of ridge-induced vertical strain.
The eleventh chapter, by Suzanne Mahlburg Kay (Cornell University) and Beatriz Coira (Consejo
Nacional de Investigaciones Científi cas y Técnicas, Argentina), presents an overview of the Neogene evolu-
tion and uplift of the Central Andean Altiplano-Puna Plateau, which is the world’s highest and most extensive
plateau formed in the absence of continental collision. Magmatic, geophysical, and structural data are used
to construct lithospheric-scale models of three distinctive transects in the southern Altiplano, northern Puna,
and southern Puna regions that reveal variable roles for shallowing and steepening of the subducting plate,
crustal shortening, delamination of thickened lower crust and lithosphere, mantle and crustal melting, and
deep crustal fl ow. Temporal similarities in processes in these transects are correlated with changes in the rate
of westward drift of South America and slab rollback, and along-strike temporal differences are correlated
viii Preface
with variations in Nazca plate geometry that refl ect the southward progression of the subduction of the
aseismic Juan Férnandez Ridge. The large concentration of giant ignimbrites in the northern Puna region is
attributed to the greatest change in slab geometry above a region where an early Miocene amagmatic fl at slab
was followed by steepening slab angles, leading to a massive ignimbrite fl are-up.
The twelfth chapter, by Patricia Alvarado (Universidad Nacional de San Juan, Argentina), Mario Pardo
(Universidad de Chile), Hersh Gilbert (Purdue University), Silvia Miranda (Universidad Nacional de San
Juan, Argentina), Megan Anderson (Colorado College), Mauro Saez (Universidad Nacional de San Juan),
and Susan Beck (University of Arizona), presents a discussion of the seismic characteristics of the Chilean-
Pampean fl at-slab region, with a particular emphasis on the region under the Sierras Pampeanas in central
Argentina. The paper reviews and presents new results from regional seismic networks on the seismicity and
shape of the subducted Nazca plate, the lithospheric structure above the fl at-slab region, and the character of
the overlying crust. The seismic character of the crust is explored in terms of inheritance of crustal properties
from the pre-Mesozoic terranes that are thought to characterize the crust in the region and a model of partial
eclogitization of a thickened crust in the western region. This chapter complements the geological discussion
of the Chilean-Pampean fl at-slab region in the fi eld guides (see below).
The overviews in volume 13 of the Geological Society of America Field Guide series round out the
discussion of processes in central and southern South America. The two chapters by Ramos feature the
Paleozoic through Neogene evolution of the modern amagmatic Pampean fl at-slab region over the shallowly
subducting Nazca plate. The fi rst emphasizes the Argentine Frontal and Main Andean Cordilleras near the
southern boundary of the fl at-slab segment, and the second features a transect from the Sierras Pampeanas
across the Precordillera fold-and-thrust belt through the main Andean Range to Chile. There is a parallelism
here with western North American geology as the evolution of the Pampean fl at slab region is the most quoted
analogue in analyses of the North American Laramide orogeny. The chapter by Zapata, Zamora Valcarce,
Folguera, and Yagupsky highlights the Andean Cordillera and retroarc of the Neuquén Andes in Argentina
(~38.5°S to 37°S) in a region where both contractional and extensional deformation have occurred. The text
discusses the multiple Cretaceous to Holocene deformational events, which are interpreted with respect to
changes in the confi guration of the convergent plate boundary and the dip of the subducting slab.
The chapter by Kay, Coira, and Mpodozis highlights the Neogene evolution of the southern Puna pla-
teau between 23°S and 27.5°S latitude and the southernmost Central Andean volcanic zone arc in Chile
at 26.5°S to 27.5°S latitude. The text emphasizes the magmatic record, particularly, the giant Cerro Galán
ignimbrites and distinctive mafi c fl ows of the southern Puna region, the late Miocene to Pliocene migration
of the frontal magmatic arc from the Maricunga belt to the Central volcanic zone, and the implications for
forearc subduction-erosion.
Finally, the chapter by Gorring highlights the region in southern Patagonia, east of the Chile triple junc-
tion region, near where ridge-trench collision is occurring at 46.5°S latitude. The text features the southern
Patagonian Cordillera, where distinctive backarc deformational and magmatic features refl ect the northward-
propagation of a series of slab windows related to ridge-trench collisional events beginning at ca. 14 Ma.
Last, the editors would like to sincerely thank all of the reviewers for their constructive comments on
the papers. In alphabetical order, the reviewers were: Christopher Andronicos (Cornell University), Larry D.
Brown (Cornell University), Elena Centeno Garcia (Universidad Nacional Autónoma de México, Mexico),
Peter Clift (University of Aberdeen, UK), Darrel S. Cowan (University of Washington), Jelle de Boer (Wes-
leyan University, USA), Donna Eberhart-Phillips (University of California, Davis), Jaillard Etienne (IRD–
LGCA [Institut de Recherche pour le Développment–Laboratoire de Géodynamique des Chaînes Alpines],
Maison des Géosciences, France), Andreas Folguera (Universidad de Buenos Aires, Argentina), John Geiss-
man (University of New Mexico), Estanislao Godoy (Servicio Nacional de Geología y Minería, Chile), Ste-
phen Grand (University of Texas, Austin), Jeffrey Hedenquist (consultant, Canada), Teresa Jordan (Cornell
University), Robert Kay (Cornell University), David Lageson (Montana State University), Stephen Marshak
(University of Illinois), René Maury (Université de Bretagne Occidentale, France), Tony Monfret (Nice Uni-
versity, France), Constantino Mpodozis (Antofagasta Minerals, Chile), Jairo Alonso Osorio Naranjo (Colom-
bian Geological Survey, Bogotá), Warren Pratt (consultant, Great Britain), Jose A. Perello (Antofagasta Min-
erals SA, Santiago, Chile), Augusto Rapalini (Universidad de Buenos Aires, Argentina), Jeremy Richards
(University of Alberta, Canada), Pablo Samaniengo (Escuela Politécnica Nacional, Ecuador), Eric Sandvol
(University of Missouri), David Scholl (U.S. Geological Survey, Menlo Park), Walter Snyder (Boise State
Preface ix
University), Robert Trumbull (GeoForschungsZentrum Potsdam, Germany), Gene Yogodzinski (University
of South Carolina), and Dante Morán Zenteno (Universidad Nacional Autónoma de México, Mexico).
REFERENCE CITED
Kay, S.M., and Ramos, V.A., eds., 2008, Field Trip Guides to the Backbone of the Americas in the Southern and Central Andes: Ridge
Collision, Shallow Subduction, and Plateau Uplift: Boulder, Colorado, Geological Society of America Field Guide 13, 181 p.