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Morphotectonic Zones Along the Coast of the Pacific Continental Margin, Southern Mexico

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Morphotectonic Zones Along the Coast of the Pacific Continental Margin, Southern Mexico See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/223022792 Morphotectonic zones along the coast of the Pacific continental margin, southern Mexico Article in Geomorphology · July 1999 DOI: 10.1016/S0169-555X(99)00016-1 CITATIONS READS 37 76 2 authors, including: J. Urrutia Fucugauchi Universidad Nacional Autónoma de México 542 PUBLICATIONS 18,205 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: CHICAGO View project Arco magmático Pérmico relacionado con la zona de sutura Ouachita en Chihuahua, México View project All content following this page was uploaded by J. Urrutia Fucugauchi on 31 January 2014. The user has requested enhancement of the downloaded file. Geomorphology 28 Ž1999. 237–250 Morphotectonic zones along the coast of the Pacific continental margin, southern Mexico Marıa-Teresa´ Ramırez-Herrera´ a,), Jaime Urrutia-Fucugauchi b,1 a Instituto de Geografıa,´ Departamento de Geografıa´ Fısica,´ UNAM, Ciudad UniÕersitaria, C.P. 04510, Mexico, D.F., Mexico b Instituto de Geofısica,´ Laboratorio de Paleomagnetismo y Geofısica´ Nuclear, UNAM, Ciudad UniÕersitaria, C.P. 04510 Mexico, D.F., Mexico Received 15 December 1997; received in revised form 20 August 1998; accepted 22 November 1998 Abstract Geomorphic analysis, employing topographic, morphologic, geologic, and bathymetric maps, and field studies show that the morphology of the southern coast of Mexico can be linked to lateral variations in the geometry and tectonism of the subduction zone. A reconnaissance study, based on the regional morphological characteristics and correlation with seismotectonic segments, regional tectonics and major bathymetric features, allows identification of several morphotectonic zones along the coast of southern Mexico: Ž1. Jalisco zone, Ž2. Colima zone, Ž3. Michoacan zone, Ž4. Guerrero zone, Ž5. Oaxaca zone, and Ž6. Tehuantepec zone. A range of geomorphological evidence, including marine terraces, river terraces, uplifted notches, and elevated wave-cut platforms, indicates local and regional uplift along the coast of the Jalisco, Michoacan, Guerrero and Oaxaca zones. Coasts of the Colima and Tehuantepec zones show morphological evidence of subsidence. q 1999 Elsevier Science B.V. All rights reserved. Keywords: active tectonics; southern Mexico; convergent margin; marine terrace; sea level; coastal geomorphology 1. Introduction terraces, each produced by a separate earthquake, may be present; this has been observed in California, Studies of how landforms evolve in a response to Alaska, New Zealand, Japan, and elsewhere Že.g., active tectonics and seismicity along coastal zones Plafker, 1965; Bull and Cooper, 1986, Ota, 1986, are crucial in determining earthquake potential and Lajoie et al., 1991; Keller and Pinter, 1996.. This assessing earthquake hazard and risk. Coseismic up- kind of analysis is needed along the coasts of the lift in coastal areas may produce a single marine active continental margin of southern Mexico. terrace. Dating the terrace then establishes when the The geomorphic response to active tectonics has earthquake occurred. Sometimes, a series of uplifted been observed in the coast along the Pacific Ocean in South, Central and North America. Studies of marine terraces along the Peruvian coast, above the ) Corresponding author. Tel.: q52-5-622-4335; Fax: q52-5- 616-0539; E-mail: [email protected] subducting Nazca ridge, have demonstrated different 1 E-mail: [email protected] rates of uplift in this area ŽHsu, 1992.. Along the 0169-555Xr99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S0169-555XŽ99.00016-1 238 M.-T. Ramırez-Herrera, ´ J. Urrutia-Fucugauchi r Geomorphology 28 ( 1999 ) 237 – 250 Fig. 1. Tectonic setting and Morphotectonic zones along the coasts of southern Mexico. Symbols: MAT—Middle American Trench, EPR—East Pacific Rise, EGG—El Gordo Graben, Fz—fault zone, J—Jalisco block, C—Colima graben, MVB—Mexican Volcanic Belt, CA—Central America, bc—Balsas submarine canyon, oc—Ometepec submarine canyon. Insert shows age in Ma ŽKlitgord and Mammerickx, 1982. and convergence rate Žcmryr. ŽDeMets and Stein, 1990. of the subducting plates at the Middle American Trench ŽPardo, 1993.. Square shows location of Deep Sea Drilling project Leg 66 transects ŽMoore et al., 1982; Watkins et al., 1982.. Site names: b—Bahia de Banderas, m—Manzanillo, l—Lagunillas, z—Zihuatanejo-Ixtapa, t—Tecpan, o—Ometepec, pm—Punta Maldonado, e—Puerto Escondido, a—Puerto Angel, s—Salina Cruz. M.-T. Ramırez-Herrera,´ J. Urrutia-FucugauchirGeomorphology 28 (1999) 237–250 239 coast of Isla Mocha, south-central Chile, 18 raised plates, divides the major tectonic provinces and sub- shorelines record rapid tectonic uplift ŽNelson and duction zone to the northwest and southeast. Manley, 1992.. Peruvian and Chilean palaeo-shore- lines have been investigated and dated. Studies have concluded that marine terraces lie at present altitudes 2. Tectonic setting because of tectonic uplift and not because former interglacial sea levels were higher than modern sea The Middle American trench ŽMAT. extends levels ŽHsu, 1992; Clapperton, 1993.. Holocene ma- along the southwestern coast of Mexico ŽFig. 1.. It is rine terraces, beach ridge complexes, and the continuous at depths greater than 4400 m for 2333 Pliocene–Pleistocene stratigraphic record on the Pa- km, except off Manzanillo and Zihuatanejo, Mexico, cific coast of Costa Rica have been used to establish and where submarine mountains lie within the trench. rates of uplift and constrain a dynamic model for Northwest of Acapulco, the trench is generally U- subduction of the Cocos Ridge and resulting uplift of shaped in cross section, with a steeper shoreward the overriding Caribbean Plate ŽGardner et al., 1992.. flank and a flat bottom, suggesting sedimentary fill. Emergent Quaternary marine terraces along the Cali- From Acapulco southeast to the western side of the fornia coast have been extensively studied to assess Gulf of Tehuantepec, the trench shoals to 5000 m in the locations, styles, and rates of Quaternary defor- a series of basins. The southeast segment is also mation ŽHanson et al., 1994; Lettis and Hall, 1994.. asymmetrical in cross section and is V-shaped with The Pacific coastal region of southern Mexico an irregular bottom. A northeast-trending band of extends across the tectonic boundary of an active ridge-and-trough topography, 111 km wide, sepa- convergent margin, characterised by subduction of rates the 3276 m to 3458 m sea floor outside the the Cocos and Rivera plates beneath the North trench off southern Mexico from the 3822 m to 4004 America plate ŽFig. 1.. Differences in the geometry m Guatemala Basin. This zone has been traced from of subduction and in the rates of convergence be- several hundred kilometres offshore to an intersec- tween the North American plate and the Cocos and tion with the trench near the western side of the Gulf Rivera plates are reflected in differences in rates of of Tehuantepec ŽFisher, 1961.. observed seismicity. Although the basic geophysical Cores recovered from eight sites drilled along characteristics of the continental margin in southern transects across the MAT off southwestern Mexico Mexico have been studied and regionally established ŽFig. 1. showed trench sands ranging in age from Že.g., Fisher, 1961; Watkins et al., 1982; DeMets and Pleistocene to Miocene. They are uplifted as much as Stein, 1990; Ponce et al., 1992; Pardo, 1993; Pardo 2 to 3 km above the present-day trench floor by and Suarez, 1995., description and interpretation of ´ combined accretion and underplating, suggesting an possible linkages between the geometry of the sub- early Miocene age Ž23–20 Ma. for the MAT ŽMoore duction zone and regional physiography have not et al., 1982; Watkins et al., 1982.. been studied. This paper focuses on a regional reconnaissance to identify possible associations between the geome- 2.1. RiÕera–North America and Cocos–North Amer- try of the subduction zone and regional physiography ica by analysing selected areas from the coastal zone along the strike of the Mexican subduction zone. The boundaries of the Rivera plate are the Rivera Landscape associations within tectonic domains are fracture zone, the East Pacific Rise ŽEPR., the described. This study covers the continental margin Tamayo fracture zone and the MAT ŽFig. 1.. The onshore Žcoastal zone. from Jalisco Ž218N, 1058W. Rivera–Cocos plate boundary consists of three dis- to Tehuantepec Ž158N, 958W., with a total length of tinct morphotectonic zones. The easternmost zone, about 1350 km. These boundaries are selected based delineated by El Gordo graben, is a zone of litho- on geographic and tectonic characteristics. The spheric extension. The westernmost zone, delineated Tehuantepec isthmus area, characterised by the triple by a regional bathymetric high, is a structurally junction of Cocos, North American, and Caribbean complex zone formed as a result of rift propagation 240 M.-T. Ramırez-Herrera,´ J. Urrutia-FucugauchirGeomorphology 28 (1999) 237–250 and convergence between the Rivera and Cocos plate is 16 to 12 Ma Žmiddle Miocene.. Elsewhere in plates. The central zone, delineated by normal this region, age of Cocos plate is late Miocene– oceanic depths and continuous sea floor spreading, Pliocene ŽKlitgord and Mammerickx, 1982; Ponce et produced magnetic lineations and is a zone of undis- al., 1992.. A change in the dip of the slab
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