DOCSLIB.ORG

Tectonic Segmentation of the North Andean Margin: Impact of the Carnegie Ridge Collision

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tectonic Segmentation of the North Andean Margin: Impact of the Carnegie Ridge Collision ELSEVIER Earth and Planetary Science Letters 168 (1999) 255±270 Tectonic segmentation of the North Andean margin: impact of the Carnegie Ridge collision M.-A. Gutscher a,Ł, J. Malavieille a, S. Lallemand a, J.-Y. Collot b a Laboratoire de GeÂophysique et Tectonique, UMR 5573, Universite Montpellier II, Place E. Bataillon, F-34095 Montpellier, Cedex 5, France b IRD, Geosciences Azur, Villefranche-sur-Mer, France Received 17 July 1998; accepted 2 March 1999 Abstract The North Andean convergent margin is a region of intense crustal deformation, with six great subduction earthquakes Mw ½ 7:8 this century. The regional pattern of seismicity and volcanism shows a high degree of segmentation along strike of the Andes. Segments of steep slab subduction alternate with aseismic regions and segments of ¯at slab subduction. This segmentation is related to heterogeneity on the subducting Nazca Plate. In particular, the in¯uence of the Carnegie Ridge collision is investigated. Four distinct seismotectonic regions can be distinguished: Region 1 ± from 6ëN to 2.5ëN with steep ESE-dipping subduction and a narrow volcanic arc; Region 2 ± from 2.5ëN to 1ëS showing an intermediate-depth seismic gap and a broad volcanic arc; Region 3 ± from 1ëS to 2ëS with steep NE-dipping subduction, and a narrow volcanic arc; Region 4 ± south of 2ëS with ¯at subduction and no modern volcanic arc. The Carnegie Ridge has been colliding with the margin since at least 2 Ma based on examination of the basement uplift signal along trench-parallel transects. The subducted prolongation of Carnegie Ridge may extend up to 500 km from the trench as suggested by the seismic gap and the perturbed, broad volcanic arc. These ®ndings con¯ict with previous tectonic models suggesting that the Carnegie Ridge entered the trench at 1 Ma. Furthermore, the anomalous geochemical (adakitic) signature of the volcanoes in the broad Ecuador volcanic arc and the seismicity pattern are proposed to be caused by lithospheric tears separating the buoyant, shallowly subducting Carnegie Ridge from segments of steep subduction in Regions 1 and 3. It is further suggested that Carnegie Ridge supports a local `¯at slab' segment similar to that observed in Peru. The impact of the Carnegie Ridge collision on the upper plate causes transpressional deformation, extending inboard to beyond the volcanic arc with a modern level of seismicity comparable to the San Andreas fault system. The pattern of instrumental and historical seismicity indicates (1) great earthquakes on the northern and southern ¯anks of the colliding ridge, (2) a slight reduction in observed seismicity at the trench±ridge intersection, (3) increased stress far into the continent, and (4) a NNE displacement of the N. Andes block, to be further effects of the collision. 1999 Elsevier Science B.V. All rights reserved. Keywords: Northern Andes; plate collision; tectonics; seismicity; segmentation; earthquakes Ł Corresponding author. Fax: C33-467-523908; E-mail: [email protected] 0012-821X/99/$ ± see front matter 1999 Elsevier Science B.V. All rights reserved. PII: S0012-821X(99)00060-6 256 M.-A. Gutscher et al. / Earth and Planetary Science Letters 168 (1999) 255±270 1. Introduction and tectonic setting reactivated in three subsequent events from south to north, in 1942, 1958 and 1979 [1,2]. This region, The North Andean margin is a region of intense frequently cited when discussing models of segment crustal deformation, in particular where Carnegie rupture, earthquake propagation and recurrence in- Ridge is subducting beneath Ecuador (Fig. 1). This tervals [1±4], was also the site of the large Mw D 7:1 section of the subduction zone has produced six earthquake, August 4, 1998. The region of great- great (de®ned as Mw > 7:75) earthquakes this cen- est seismicity coincides with the subducted northern tury. The largest in 1906 (Mw D 8:8) had an esti- ¯ank of Carnegie Ridge. Unlike other subduction mated rupture zone of ca. 500 km length, partially zones, in the North Andes instrumental and histori- 10˚N Plate Motions Caribbean Plate Global Model NUVEL-1 (De Mets et al., 1990) 7.2 cm/a 8˚N GPS 9.1 cm/a Panama FZ (Kellogg and Vega, 1995) 5 6˚N Cocos Coiba R. North 4 7.0 cm/a Plate Cocos Ridge 5.0 cm/a Andes 6-7 3 Block cm/a 6-7 4˚N cm/a 2 Malpelo R. Panama 5B 2 4 Rift DGM 2 5A 3 Malp. Yaquina 3 Rift Graben 2˚N 2 2 5A 2500m 4 7.0 cm/a 5B 2 7.0 cm/a 5 0˚ Galapagos 3 Islands Coastal R. Explanation Carnegie Ridge Brazilian Shield 2˚S Subduction Zone Active Volcano Thrust Fault Mangrove Swamp Nazca GG Spreading Center Drainage Basin w. Plate (active) Outflow Direction 4˚S Spreading Center (inactive) Oceanic Plateau Grijalva FZ (2500 m contour) Figures 2,3 Alvarado R. Transform Sarmiento R.10 Coastal Relief 6˚S 200 m, 400 m Farallon Ocean Crust9 Strike Slip Fault 8 Inferred Fault or 3 Magnetic 7 Anomaly Subducted Structure 8˚S 95˚W 85˚W 80˚W 90˚W 75˚W Fig. 1. Tectonic setting of the study area showing major faults, relative plate motions according to GPS data [7] and the NUVEL-1 global kinematic model [8], magnetic anomalies [13] and active volcanoes [50]. Here and in Fig. 4, the locations of the 1906 (Mw D 8:8, very large open circle) and from south to north, the 1953, 1901, 1942, 1958 and 1979 (M ½ 7:8, large open circles) earthquakes are shown. GG D Gulf of Guayaquil; DGM D Dolores±Guayaquil Megashear. M.-A. Gutscher et al. / Earth and Planetary Science Letters 168 (1999) 255±270 257 cal seismicity M ½ 7 extend hundreds of kilometers place ca. 25 Ma, breaking the Farallon Plate into inland and beyond the volcanic arc. The current de- the Cocos and Nazca plates to the south and the bate on seismic coupling in subduction zones [5,6] Juan de Fuca Plate farther to the north [12]. Due and its relation to subducting bathymetric highs (as- to differential stresses on the northeastward-subduct- perities) bears strongly on the entire area and on the ing Cocos Plate and the eastward-subducting Nazca assessment of its seismic risk. Plate, spreading was initiated around 23 Ma be- Recent advances in instrumentation and computer tween the two plates in the vicinity of the Galapagos technology and availability of satellite-derived data hotspot and later evolved into the current-day Gala- present a unique opportunity to combine indepen- pagos Rift with N±S spreading [13,14]. The Grijalva dent, high resolution, digital data sets from a va- scarp, an old N60ëE fracture zone in the Farallon riety of ®elds (seismology, volcanology, morphol- Plate, is interpreted to represent the southern half of ogy=topography, satellite altimetry, GPS±geodetic the scar where the Nazca Plate tore off. Carnegie studies, structural geology) for application to geo- and Cocos ridges are mirror-image hotspot traces dynamic problems. The principal objective of this formed by the northeastward motion of the Cocos study is to re-examine the seismicity and tectonics Plate and the eastward motion of the Nazca Plate in this region of intense crustal deformation in view over the Galapagos hotspot [13±16]. According to of these newly available data. By studying the spa- this model both Cocos and Carnegie ridges arrived at tial distribution of hypocenters and examining focal their respective trenches 1 Ma [13]. mechanisms we aim to identify the principal fault Most models suggest that Malpelo Ridge is a planes, identify areas prone to large earthquakes and former continuation of Cocos Ridge separated by scrutinize apparent seismic gaps. Correlations be- dextral motion along the N±S-trending Panama FZ tween structural heterogeneity of the oceanic Nazca [13,14]. Malpelo and Carnegie ridges separated from Plate and uplift, deformation and volcanism in the one another during a period of rifting and sea¯oor overriding South American Plate should improve spreading from ca. 17 to 8 Ma [13,15,17]. The ex- our understanding of these processes and of the pressions of the extinct Malpelo Rift and adjacent overall lithospheric structure of an oceanic plateau± rift segments as well as the transform faults separat- subduction zone collision. ing them are clearly visible in the morphology of the Along the North Andean margin, the Nazca Plate sea¯oor (Fig. 2). is subducting eastwards beneath South America at arateof5±7cm=a [7,8] (Fig. 1). Simultane- ously, the North Andean block is being displaced 2. Seismicity database and observations to the northeast at a rate of ca. 1 cm=a along the Dolores±Guayaquil Megashear accounting for the Earthquake data in the study area were obtained discrepancy between the global model (Nazca mo- from Engdahl et al.'s recent global relocation effort tion relative to stable South America) [2] and the [18], improving hypocenter locations from the Inter- GPS measurements (Nazca motion relative to the national Seismological Centre (ISC) Catalog. Thus, North Andes block [7,9] (Fig. 1). Thus, the ENE-ori- for this study area 1230 events Mb > 4:0 from ented Carnegie Ridge is sweeping southwards along January 1964 to December 1995 were available. Cat- the Ecuador margin. Recent coastal uplift facing alogs of lesser quality but (1) covering a greater time Carnegie Ridge is indicated by Pliocene marine ter- span (the South American SISRA Catalog [19] ca. races (Tablazos) exposed at 200±300 m elevations 800 events Mb > 4:0 from 1900 to 1972), or (2) [10,11]. To the north, the morphology, widespread comprising more events (the USGS PDE ± Prelim- mangrove swamps and neotectonics of the South inary Determination of Earthquakes ± Catalog; ca.
Load more

Recommended publications
  • Cambridge University Press 978-1-108-44568-9 — Active Faults of the World Robert Yeats Index More Information
    Cambridge University Press 978-1-108-44568-9 — Active Faults of the World Robert Yeats Index More Information Index Abancay Deflection, 201, 204–206, 223 Allmendinger, R. W., 206 Abant, Turkey, earthquake of 1957 Ms 7.0, 286 allochthonous terranes, 26 Abdrakhmatov, K. Y., 381, 383 Alpine fault, New Zealand, 482, 486, 489–490, 493 Abercrombie, R. E., 461, 464 Alps, 245, 249 Abers, G. A., 475–477 Alquist-Priolo Act, California, 75 Abidin, H. Z., 464 Altay Range, 384–387 Abiz, Iran, fault, 318 Alteriis, G., 251 Acambay graben, Mexico, 182 Altiplano Plateau, 190, 191, 200, 204, 205, 222 Acambay, Mexico, earthquake of 1912 Ms 6.7, 181 Altunel, E., 305, 322 Accra, Ghana, earthquake of 1939 M 6.4, 235 Altyn Tagh fault, 336, 355, 358, 360, 362, 364–366, accreted terrane, 3 378 Acocella, V., 234 Alvarado, P., 210, 214 active fault front, 408 Álvarez-Marrón, J. M., 219 Adamek, S., 170 Amaziahu, Dead Sea, fault, 297 Adams, J., 52, 66, 71–73, 87, 494 Ambraseys, N. N., 226, 229–231, 234, 259, 264, 275, Adria, 249, 250 277, 286, 288–290, 292, 296, 300, 301, 311, 321, Afar Triangle and triple junction, 226, 227, 231–233, 328, 334, 339, 341, 352, 353 237 Ammon, C. J., 464 Afghan (Helmand) block, 318 Amuri, New Zealand, earthquake of 1888 Mw 7–7.3, 486 Agadir, Morocco, earthquake of 1960 Ms 5.9, 243 Amurian Plate, 389, 399 Age of Enlightenment, 239 Anatolia Plate, 263, 268, 292, 293 Agua Blanca fault, Baja California, 107 Ancash, Peru, earthquake of 1946 M 6.3 to 6.9, 201 Aguilera, J., vii, 79, 138, 189 Ancón fault, Venezuela, 166 Airy, G.
    [Show full text]
  • Structure of the Collision Zone Between the Nazca Ridge and the Peruvian Convergent Margin
    RESEARCH ARTICLE Structure of the Collision Zone Between the Nazca Ridge 10.1029/2019TC005637 and the Peruvian Convergent Margin: Geodynamic Key Points: • The Nazca Ridge hosts an and Seismotectonic Implications overthickened lower crust E. Contreras‐Reyes1 , P. Muñoz‐Linford2, V. Cortés‐Rivas1, J. P. Bello‐González3, J. A. Ruiz1, (10–14 km) formed in an on‐ridge 4 setting (hot spot plume near a and A. Krabbenhoeft spreading center) 1 2 • The Nazca Ridge correlates with a Departamento de Geofísica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile, Centro prominent continental slope scarp I‐MAR, Universidad de los Lagos, Puerto Montt, Chile, 3Grupo Minero Las Cenizas, Taltal, Chile, 4GEOMAR‐Helmholtz bounded by a narrow and uplifted Centre for Ocean Research, Kiel, Germany continental shelf • The Nazca Ridge has behaved as a seismic asperity for moderate earthquakes (e.g., 1996 Mw 7.7 and Abstract We study the structure and tectonics of the collision zone between the Nazca Ridge (NR) and 2011 Mw 6.9) nucleating at depths the Peruvian margin constrained by seismic, gravimetric, bathymetric, and natural seismological data. >20 km The NR was formed in an on‐ridge setting, and it is characterized by a smooth and broad shallow seafloor (swell) with an estimated buoyancy flux of ~7 Mg/s. The seismic results show that the NR hosts an Supporting Information: – – • Supporting Information S1 oceanic lower crust 10 14 km thick with velocities of 7.2 7.5 km/s suggesting intrusion of magmatic material from the hot spot plume to the oceanic plate. Our results show evidence for subduction erosion in the frontal part of the margin likely enhanced by the collision of the NR.
    [Show full text]
  • Seismic Imaging of the Structure of the Central Ecuador Convergent Margin : Relationship with the Inter-Seismic Coupling Variations Eddy Sanclemente Ordońez
    Seismic imaging of the structure of the central Ecuador convergent margin : relationship with the inter-seismic coupling variations Eddy Sanclemente Ordońez To cite this version: Eddy Sanclemente Ordońez. Seismic imaging of the structure of the central Ecuador convergent margin : relationship with the inter-seismic coupling variations. Earth Sciences. Université Nice Sophia Antipolis, 2014. English. NNT : 2014NICE4030. tel-01005320 HAL Id: tel-01005320 https://tel.archives-ouvertes.fr/tel-01005320 Submitted on 12 Jun 2014 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITE DE NICE-SOPHIA ANTIPOLIS - UFR Sciences École Doctorale de Sciences Fondamentales et Appliquées T H E S E pour obtenir le titre de : Docteur en Sciences de l'UNIVERSITÉ de Nice-Sophia Antipolis Discipline : Sciences de la Planète et de l’Univers présentée et soutenue par Eddy SANCLEMENTE IMAGERIE SISMIQUE DE LA STRUCTURE DE LA MARGE CONVERGENTE D’EQUATEUR CENTRAL : RELATIONS AVEC LES VARIATIONS DE COUPLAGE INTERSISMIQUE SEISMIC IMAGING OF THE STRUCTURE OF THE CENTRAL ECUADOR CONVERGENT MARGIN: RELATIONSHIP WITH THE INTER-SEISMIC COUPLING VARIATIONS Thèse dirigée par : Jean-Yves COLLOT et Alessandra RIBODETTI soutenue le 28 Mai 2014 Jury : M. Bertrand Delouis, Professeur, Examinateur M.
    [Show full text]
  • Tectonic Segmentation of the North Andean Margin: Impact of the Carnegie Ridge Collision
    ELSEVIER Earth and Planetary Science Letters 168 (1999) 255±270 Tectonic segmentation of the North Andean margin: impact of the Carnegie Ridge collision M.-A. Gutscher a,Ł, J. Malavieille a, S. Lallemand a, J.-Y. Collot b a Laboratoire de GeÂophysique et Tectonique, UMR 5573, Universite Montpellier II, Place E. Bataillon, F-34095 Montpellier, Cedex 5, France b IRD, Geosciences Azur, Villefranche-sur-Mer, France Received 17 July 1998; accepted 2 March 1999 Abstract The North Andean convergent margin is a region of intense crustal deformation, with six great subduction earthquakes Mw ½ 7:8 this century. The regional pattern of seismicity and volcanism shows a high degree of segmentation along strike of the Andes. Segments of steep slab subduction alternate with aseismic regions and segments of ¯at slab subduction. This segmentation is related to heterogeneity on the subducting Nazca Plate. In particular, the in¯uence of the Carnegie Ridge collision is investigated. Four distinct seismotectonic regions can be distinguished: Region 1 ± from 6ëN to 2.5ëN with steep ESE-dipping subduction and a narrow volcanic arc; Region 2 ± from 2.5ëN to 1ëS showing an intermediate-depth seismic gap and a broad volcanic arc; Region 3 ± from 1ëS to 2ëS with steep NE-dipping subduction, and a narrow volcanic arc; Region 4 ± south of 2ëS with ¯at subduction and no modern volcanic arc. The Carnegie Ridge has been colliding with the margin since at least 2 Ma based on examination of the basement uplift signal along trench-parallel transects. The subducted prolongation of Carnegie Ridge may extend up to 500 km from the trench as suggested by the seismic gap and the perturbed, broad volcanic arc.
    [Show full text]
  • Revised Tectonic Boundaries in the Cocos Plate Off Costa Rica Implications for the Segmentation of the Convergent Margin And
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. B9, PAGES 19,207-19,220, SEPTEMBER 10, 2001 Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models Udo Barckhausen,• Cesar R. Ranero, 2 R. von Huene, 2,• Steven C. Cande,4 and Hans A. Roeser t Abstract. The oceanicCocos Plate subductingbeneath Costa Rica has a complexplate tectonichistory resulting in segmentation.New lines of magneticdata clearlydefine tectonicboundaries which separatelithosphere formed at the East PacificRise from lithosphereformed at the Cocos-Nazcaspreading center. They also define two early phase Cocos-Nazcaspreading regimes and a major propagator.In addition to these sharply definedtectonic boundaries are overprintedboundaries from volcanismduring passageof CocosPlate over the Galapagoshot spot.The subductedsegment boundaries correspond with distinctchanges in upper plate tectonicstructure and featuresof the subductedslab. Newly identifiedseafloor-spreading anomalies show oceanic lithosphere formed during initial breakupof the FarallonPlate at 22.7 Ma and openingof the Cocos-Nazcaspreading center. A revisedregional compilation of magneticanomalies allows refinement of plate tectonicmodels for the earlyhistory of the Cocos-Nazcaspreading center. At 19.5Ma a major ridgejump reshapedits geometry,and after -14.5 Ma multiplesouthward ridge jumps led to a highly asymmetricaccretion of lithosphere.A suspectedcause of ridgejumps is an interactionof the Cocos-Nazcaspreading center
    [Show full text]
  • Tectonic Analysis of Northwestern South America from Integrated Satellite, Airborne and Surface Potential Field Anomalies
    TECTONIC ANALYSIS OF NORTHWESTERN SOUTH AMERICA FROM INTEGRATED SATELLITE, AIRBORNE AND SURFACE POTENTIAL FIELD ANOMALIES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Orlando Hernandez, B.S., M.S. ***** The Ohio State University 2006 Dissertation Committee: Approved by Dr. Ralph R. B. von Frese, Adviser Dr. Hallan C. Noltimier Adviser Dr. Michael Barton Graduate Program in Dr. Douglas E. Pride Geological Sciences °c Copyright by Orlando Hernandez 2006 ABSTRACT Northwestern South America is one of the most populated regions of the Americas with more than 80 million people concentrated along the Andes Mountains. This region includes a complex and dangerous mosaic of tectonic plates that have produced dev- astating earthquakes, tsunamis, volcanic eruptions and landslides in the last decades. The region’s economic development has also seriously suffered because the region is poorly explored for natural resources. To more effectively assess the tectonic hazards and mineral and energy resources of this region, we must improve our understanding of the tectonic setting that produced them. This research develops improved tectonic models for northwestern South America from available satellite, airborne and surface gravity and magnetic data integrated with global digital topography, seismic, and GPS plate velocity data. Reliable crustal thick- ness estimates that help constrain tectonic stress/strain conditions were obtained by inverse modeling of the magnetic anomalies and terrain compensated gravity anoma- lies. Correlated positive Terrain Gravity Effects (TGE) and Free Air Gravity Anoma- lies (FAGA) suggest that the crust - mantle interface under the northwestern Andes is closer to the surface than expected, indicating that these mountains are not iso- statically compensated.
    [Show full text]
  • Tectonics of the Panama Basin, Eastern Equatorial Pacific
    TJEERD H. VAN ANDEL" G. ROSS HEATH BRUCE T. MALFAIT Department of Oceanography. Oregon State University. Corralhs, Oregon 97331 DONALD F. HEINRICHSj JOHN I. EWING Lamont-Doherty Geological Observatory. Columbia University. Palisades. New York 10964 Tectonics of the Panama Basin, Eastern Equatorial Pacific ABSTRACT from being fully understood. Similar enigmatic The Panama Basin includes portions of the features are found at complex boundaries be- Nazca, Cocos and South America Hthospheric tween continental and oceanic plates. plates and borders the Caribbean plate. The In this paper we describe and attempt to ex- complex interactions of these units have largely plain the morphological and structural features determined the topography, pattern of faulting, of such a complex region; the area bordered on sediment distribution, and magnetic character the east and north by South and Central of the basin. Only heat flow data fail to corre- America, and on the south and west by the late with major structural features related to Carnegie and Cocos Ridges. This region (Fig. these units. 1) contains the aseismic Cocos and Carnegie The topographic basin appears to have been Ridges, portions of the Peru and Middle created by rifting of an ancestral Carnegie America Trenches, an actively spreading east- Ridge. The occurrence of a distinctive smooth west rift zone, several major fracture zones, a acoustic basement and a characteristic overly- complex continental margin between the ex- ing evenly stratified sedimentary sequence on treme ends of the two trenches, and the large virtually all elevated blocks in the basin suggest volcanic block of the Galapagos Islands. It en- that they all once formed part of this ancestral compasses portions of the Pacific, Nazca, South ridge.
    [Show full text]
  • Structure of the Malpelo Ridge (Colombia) from Seismic and Gravity Modelling
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/225334814 Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling Article in Marine Geophysical Researches · January 2006 DOI: 10.1007/s11001-006-9009-y CITATIONS READS 13 273 3 authors: Boris Marcaillou P. Charvis University of Nice Sophia Antipolis Institute of Research for Development 59 PUBLICATIONS 561 CITATIONS 196 PUBLICATIONS 3,807 CITATIONS SEE PROFILE SEE PROFILE jean-yves Collot Institute of Research for Development 421 PUBLICATIONS 2,135 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Ecuadorian Active margin studies View project Sisteur Project View project All content following this page was uploaded by P. Charvis on 10 March 2014. The user has requested enhancement of the downloaded file. Mar Geophys Res DOI 10.1007/s11001-006-9009-y ORIGINAL PAPER Structure of the Malpelo Ridge (Colombia) from seismic and gravity modelling Boris Marcaillou Æ Philippe Charvis Æ Jean-Yves Collot Received: 27 March 2006 / Accepted: 28 August 2006 Ó Springer Science+Business Media B.V. 2006 Abstract Wide-angle and multichannel seismic data Keywords Malpelo ridge Æ Galapagos hot spot Æ collected on the Malpelo Ridge provide an image of Cocos-Nazca spreading centre Æ Wide angle seismic Æ the deep structure of the ridge and new insights on Multichanel seismic its emplacement and tectonic history. The crustal structure of the Malpelo Ridge shows a 14 km thick asymmetric crustal root with a smooth transition to Geological setting: tectonic history of the Panama the oceanic basin southeastward, whereas the transi- Basin tion is abrupt beneath its northwestern flank.
    [Show full text]
  • A Pliocene–Quaternary Compressional Basin in the Interandean Depression, Central Ecuador
    Geophys. J. Int. (1995) 121,279-300 A Pliocene-Quaternary compressional basin in the Interandean Depression, Central Ecuador Alain Lavenu,' ,2 Thierry Winter3* and Francisco D6vila4 'ORSTOM, UR 13, TOA, 213 rue La Fayette. 75480 Purls cedex 10. France 'Laboraroire de GPodynamique er ModPlisation des Bassins Sidimenraires, UPPA, auenue dr I'UnivrrsiiP, 64 000 Pau, France .'Laborntoire de Tectonique. MCcanique cie la Lirhosphe're, IPGP, 4 place Jussieu, 75 252 Paris cedex 05, France 'Depurtarnento de Geologiu, EPN, Ap. 2759, Olrito, Ecuador Downloaded from Accepted 1994 September 29. Received 1994 September 29; in original form 1993 April 12 SUMMARY The segment of the Interandean Depression of Ecuador between Ambato and Quito http://gji.oxfordjournals.org/ is characterized by an uppermost Pliocene-Quaternary basin, which is located between two N-S trending reverse basement faults: the Victoria Fault to the west, and the Pisayambo Fault to the east. The clear evidence of E-W shortening for the early Pleistocene (between 1.85 and 1.21 Ma) favours a compressional basin interpretation. The morphology (river deviations, landslides, folded and flexure structures) demonstrates continuous shortening during the late Quaternary. The late Pliocene-Quaternary shortening reached 3400 f 600 m with a rate of 1.4 f at INST GEOLOGICO MINERO Y METALURGICO on May 3, 2013 0.3 mm yr-'. The E-W shortening is kinematically consistent with the current right-lateral reverse motion along the NE-SW trending Pallatanga Fault. The Quito-Ambato zone appears to act as a N-S restraining bend in a system of large right-lateral strike-slip faults.
    [Show full text]
  • Tectonic Evolution of the Andes of Ecuador, Peru, Bolivia and Northern
    CORDANI, LJ.G./ MILANI, E.J. I THOMAZ flLHO. A.ICAMPOS. D.A. TECTON IeEVOLUTION OF SOUTH AMERICA. P. 481·559 j RIO DE JANEIRO, 2000 TECTONIC EVOLUTION OF THE ANDES OF ECUADOR, PERU, BOLIVIA E. Jaillard, G. Herail, T. Monfret, E. Dfaz-Martfnez, P. Baby, A, Lavenu, and J.F. Dumont This chapterwasprepared underthe co-ordination chainisvery narrow. Thehighest average altitudeisreached ofE.[aillard. Together withG.Herail andT. Monfret,hewrote between 15°5 and 23°S, where the Altiplano ofBolivia and the Introduction. Enrique Dfaz-Martinez prepared the southernPerureaches anearly 4000 mofaverage elevation, section on the Pre-Andean evolution ofthe Central Andes. andcorresponds tothewidest partofthechain. TheAndean Again Iaillard, onthe Pre-orogenic evolution ofthe North­ Chain is usually highly asymmetric, witha steep western Central Andes. E.[aillard, P. Baby, G. Herail.A, Lavenu, and slope. and a large and complex eastern side. In Peru,the J.E Dumont wrote the texton theorogenic evolution of the distance between the trench and the hydrographic divide North-Central Andes, And, finally, [aillard dosed the variesfrom 240 to }OO km.whereas. the distancebetween manuscript with theconclusions. thehydrographic divide and the200m contourlineranges between 280 km(5°N) and about1000 kIn (Lima Transect, 8·S - 12°5). In northern Chile and Argentina (23·5),these distances become 300 krn and 500 km, respectively. Tn INTRODUCTION: southern Peru,as littleas 240 km separates the Coropuna THE PRESENT-DAY NORTH-CENTRAL Volcano (6425 m) from the Chile-Peru Trench (- 6865 m). This, together with the western location of the Andes ANDES (jON - 23°5) _ relative to theSouth American Con tinent,explains whythe riversflowing toward the Pacific Ocean do not exceed 300 TheAndean Chain isthemajormorphological feature of kmlong, whereas thoseflowing to theAtlantic Ocean reach theSouth American Continent.
    [Show full text]
  • Impact of the Carnegie Ridge Collision
    EPSL ELSEVIER Earth und Plnnciary Scicncc Letters 16K II9YY) 255-270 I Tectonic segmentation of the North Andean margin: impact of the Carnegie Ridge collision - I? J. M.-A. Gutscher a**, Malavieille "'S. Lallemand a, J.-Y1 Collot ': Luhoruroirt de Ginphpique er %CJOIli~lIC,UMR 5573, liniversiJi Monrpellier II. Pluce E. Buiuillon. F-34UY5 Montpellier; Cedex 5. France IRD, Gcwciences AXE Villtfranchr-sur-Me%France Received i 7 July 1998: accepted 2 March 1999 " Abstract The North Andean converfent margin is a region of intense crustal deformation, with six great subduction earthquakes M, 2 7.8 this centun.. The regional pattern of seismicity and volcanism shows a high degree of segmentation along strike of the .4ndes. Serments of steep slab subduction alternate with aseismic regions and secgents of flat slab subduction. This segmentation is related to heterogeneity on the subducting Nazca Plate. In particular, the influence of the Carnegie Ridge collision is investigated. Four distinct seismotectonic regions can be distinguished Region 1 - from 6"N to 5"N with steep ESE-dipping subduction and a narrow volcanic arc: Region 3 - from 3.5"N to 1"s showing an intennediate-depth . seismic gap and ;I broad volcanic arc: Region 3 - from 1"s to 3"S.wit.h steep NE-dipping subduction. and a narrow volcanic arc: Region 3 - south of 2"s with flat subduction and no modem volcanic arc. The Carnegie Ridge has been colliding with the margin since at least 3 Ma based on examination of the basement uplift signal along trench-parallel transects. The subducted prolongation of Carnegie Ridge may extend up to 500 km from the trench as suggested by the seismic gap and the pzturbed.
    [Show full text]
  • Young Tracks of Hotspots and Current Plate Velocities
    Geophys. J. Int. (2002) 150, 321–361 Young tracks of hotspots and current plate velocities Alice E. Gripp1,∗ and Richard G. Gordon2 1Department of Geological Sciences, University of Oregon, Eugene, OR 97401, USA 2Department of Earth Science MS-126, Rice University, Houston, TX 77005, USA. E-mail: [email protected] Accepted 2001 October 5. Received 2001 October 5; in original form 2000 December 20 SUMMARY Plate motions relative to the hotspots over the past 4 to 7 Myr are investigated with a goal of determining the shortest time interval over which reliable volcanic propagation rates and segment trends can be estimated. The rate and trend uncertainties are objectively determined from the dispersion of volcano age and of volcano location and are used to test the mutual consistency of the trends and rates. Ten hotspot data sets are constructed from overlapping time intervals with various durations and starting times. Our preferred hotspot data set, HS3, consists of two volcanic propagation rates and eleven segment trends from four plates. It averages plate motion over the past ≈5.8 Myr, which is almost twice the length of time (3.2 Myr) over which the NUVEL-1A global set of relative plate angular velocities is estimated. HS3-NUVEL1A, our preferred set of angular velocities of 15 plates relative to the hotspots, was constructed from the HS3 data set while constraining the relative plate angular velocities to consistency with NUVEL-1A. No hotspots are in significant relative motion, but the 95 per cent confidence limit on motion is typically ±20 to ±40 km Myr−1 and ranges up to ±145 km Myr−1.
    [Show full text]