Origin of a restraining bend in an evolving strike-slip system: The Cenozoic As Pontes basin (NW Spain)

The As Pontes basin (12 km2), NW Iberian Peninsula, is bounded by a double restraining bend of a dextral strike-slip fault, which is related to the western onshore end of the Pyrenean belt. Surface and subsurface data obtained from intensive coal exploration and mining in the basin since the 1960s together with additional structural and stratigraphic sequence analysis allowed us to determine the geometric relationships between tectonic structures and stratigraphic markers. The small size of the basin and the large amount of quality data make the As Pontes basin a unique natural laboratory for improving our understanding of the origin and evolution of restraining bends. The double restraining bend is the end stage of the structural evolution of a compressive underlapping stepover, where the basin was formed. During the first stage (stepover stage), which began ca. 30 Ma ago (latest Rupelian) and lasted 3.4 My, two small isolated basins bounded by thrusts and normal faults were formed. For 1.3 My, the strike-slip faults, which defined the stepover, grew towards each other until joining and forming the double restraining bend, which bounds one large As Pontes basin (transition stage). The history of the basin was controlled by the activity of the double restraining bend for a further 3.4 My (restraining bend stage) and ended in mid-Aquitanian times (ca. 22 Ma).

[1]  E. Guerrero,et al.  Catchment evolution of the continental strike-slip as pontes basin (tertiary, NW Spain): constraints from the heavy mineral analysis , 2003 .

[2]  Ken McClay,et al.  Analog Modeling of Pull-Apart Basins , 1997 .

[3]  J. A. Pulgar,et al.  SEISMIC IMAGE OF THE CANTABRIAN MOUNTAINS IN THE WESTERN EXTENSION OF THE PYRENEES FROM INTEGRATED ESCIN REFLECTION AND REFRACTION DATA , 1996 .

[4]  M. Curtis.  Structural and kinematic evolution of a Miocene to Recent sinistral restraining bend: the Montejunto massif, Portugal , 1999 .

[5]  N. Woodcock,et al.  Strike-slip duplexes , 1986 .

[6]  J. A. Pulgar,et al.  Tertiary basins of Spain: Tertiary basins and Alpine tectonics in the Cantabrian Mountains (NW Spain) , 1996 .

[7]  H. Tor,et al.  Strike-slip basins , 1995 .

[8]  A. Sáez,et al.  The coal bearing Cenozoic As Pontes Basin (NW Spain): geological influence on its coal's characteristics , 1995 .

[9]  T. Davis,et al.  Seismically active fold and thrust belt in the San Joaquin Valley, central California , 1988 .

[10]  P. Mann,et al.  Neogene development of the Swan Islands restraining-bend complex, Caribbean Sea , 1991 .

[11]  P. Mann,et al.  Neotectonics of Hispaniola: plate motion, sedimentation, and seismicity at a restraining bend , 1984 .

[12]  K. McClay,et al.  Analog models of restraining stepovers in strike-slip fault systems , 2001 .

[13]  P. Mann,et al.  Development of Pull-Apart Basins , 1983, The Journal of Geology.

[14]  J. Gallart,et al.  The ESCI-N2 deep seismic reflection profile: a traverse across the Cantabrian Mountains and adjacent Duero basin , 1995 .

[15]  Neotectonics of a Strike-Slip Restraining Bend System, Jamaica , 1985 .

[16]  J. McBride.  Investigating the crustal structure of a strike-slip “step-over” zone along the Great Glen fault , 1994 .

[17]  Lluís Cabrera,et al.  Tectonic–palaeoenvironmental forcing of clay-mineral assemblages in nonmarine settings: the Oligocene–Miocene As Pontes Basin (Spain) , 2003 .

[18]  R. Steel,et al.  The Tertiary Strike-Slip Basins and Orogenic Belt of Spitsbergen , 1985 .

[19]  Lluís Cabrera,et al.  Tertiary basins of Spain: Onshore Cenozoic strike–slip basins in NW Spain , 1996 .

[20]  Leigh H. Royden,et al.  The Vienna Basin: A Thin-Skinned Pull-Apart Basin , 1985 .

[21]  N. Christie‐Blick,et al.  Deformation and Basin Formation Along Strike-Slip Faults , 1985 .

[22]  J. C. Crowell.  Sedimentation Along the San Andreas Fault California , 1974 .

[23]  A. Sylvester,et al.  Tectonic Transpression and Basement-Controlled Deformation in San Andreas Fault Zone, Salton Trough, California , 1976 .

[24]  K. McClay,et al.  Strike-slip deformation in the Confidence Hills, southern Death Valley fault zone, eastern California, USA , 1996, Journal of the Geological Society.

[25]  J. C. Crowell.  Origin of Late Cenozoic Basins in Southern California: ABSTRACT , 1973 .

[26]  T. b.  The Pyrenees , 1893, Nature.

[27]  Lluís Cabrera,et al.  Sedimentological and palaeohydrological responses to tectonics and climate in a small, closed, lacustrine system: Oligocene As Pontes Basin (Spain) , 2002 .

[28]  A. Nur,et al.  Evolution of pull‐apart basins and their scale independence , 1982 .

[29]  L. Cabrera,et al.  Basin formation at the end of a strike-slip fault: the Cerdanya Basin (eastern Pyrenees) , 1988, Journal of the Geological Society.

[30]  R. E. Wilcox,et al.  Basic Wrench Tectonics , 1973 .

[31]  N. L. Martínez,et al.  Estudio paleontológico en las cuencas terciarias de Galicia , 1993 .

[32]  P. F. S. Prat.  Las Cuencas Terciarias gallegas en la terminación occidental de los relieves pirenaicos , 1994 .

[33]  R. Miller.  A mid-crustal contractional stepover zone in a major strike-slip system, North Cascades, Washington , 1994 .

[34]  S. D. Lewis,et al.  The Marinduque intra-arc basin, Philippines: Basin genesis and in situ ophiolite development in a strike-slip setting , 1991 .

[35]  J. Alonso,et al.  La deformación alpina en el basamento varisco de la Zona Cantábrica , 1999 .

[36]  L. Cabrera,et al.  Magnetocronología de las sucesiones cenozoicas de la cuenca de As Pontes (La Coruña, Noroeste de España) , 1997 .