Panama 2010. "Subduction Zones and Bent Orogenic Belts of the Caribbean". February 8-11, 2010. Joint meeting of IGCP projects 546 "Subduction Zones of the Caribbean" and 574 "Bending and Bent Orogens, and Continental Ribbons"

ABSTRACT VOLUME

Citation: In: García-Casco, A., Montes, C., Cardona, A. (Eds.) “Subduction Zones of the Caribbean” IGCP 546 Special Contribution 4. http://www.ugr.es/~agcasco/igcp546/ >> Activities >> Panama 2010 >> Abstracts.

Workshop "Subduction Zones and Bent Orogenic Belts of the Caribbean " Panama, February 8, 2010.
Abstract Volume

IGCP-546 "Subduction zones of the Caribbean" and IGCP 574 "Bending and bent orogens" joint meeting

 

A tectono-stratigraphic map of the Greater Antilles

Nelson, Carl E.
Consulting Geologist, Recursos del Caribe, S.A., cnelson945@aol.com

Geologic maps of the Caribbean Basin generally display rock units according to their age and lithology (e.g. Late Cretaceous limestone). Few geologic maps display rock units according to their tectono-stratigraphic setting (e.g. North American platform carbonates). A preliminary 1:1,000,000 scale tectono-stratigraphic map for the Greater Antilles provides an easier-to-interpret map of the northern margin of the Caribbean Plate. Conference participants are invited to offer suggestions for improvement to both the map and the legend. Contributions will be incorporated and, at the next conference, an updated map will be presented for further review and revision. Plans are to extend this effort to the entire Caribbean Basin.

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Two-stage Neogene model for the Panama-Colombia collision

Pindell, J.
Rice University, Houston Texas. jim@tectonicanalysis.com

GPS data (e.g. Trenkamp et al. 2002) show that Panama and the Sierra Baudó are converging with South America faster (40 mm/a) than the Caribbean Plate is converging with South America (20 mm/a). Thus the tectonic escape model invoked by Wadge & Burke (1983), Mann & Corrigan (1990), and Pindell (1993), wherein slices of Panama are being backthrust to the northwest onto the Caribbean Plate, is not currently operating, although it may have done so earlier in the collision (Middle to Late Miocene). I interpret Panama to be moving relatively east with respect to South America faster than the Caribbean Plate because the base of the Panama “block” is partially coupled to the north-dipping Nazca Plate which moves east relative to South America at > 60 mm/a, 3 times faster than does the Caribbean Plate. Panama is now overthrusting Caribbean crust on Panama’s northeastern flank, and not its northwest flank as earlier models had presumed. Thus, I deduce that there should be E–W sinistral shear zones crossing Costa Rica/Panama that account for this late eastward displacement. Inspection of radar imagery shows that indeed there are variably developed topographic lineaments precisely where differences in GPS motions predict them to be, although seismicity along these zones rarely exceeds the magnitude 4 threshold witnessed by global networks. Here I employ the term “Panama Block” to denote the general area that moves east faster than the Caribbean Plate, subject to future refinement. I consider that the onset of coupling with the Nazca Plate was coeval with the ~9 Ma jump in plate boundary position from the Malpelo Ridge (where spreading is now extinct) to the Panama Fracture Zone; thus, if the Panama tectonic escape model is valid, it probably was a Middle Miocene to earliest Late Miocene phenomenon. The folds recording motion along the NW trending “escape faults” (Mann & Corrigan 1990) appear to be onlapped by flanking strata, rather folding the youngest strata, suggesting that Late Miocene termination of folding (and hence NW-ward tectonic escape) might be supported by the geology. Careful dating and structural analysis of these sediments may better demonstrate when the folds were active. This two-stage Neogene model for the ongoing Panama-Colombia collision has important implications for hydrocarbon exploration in the North Panama Foldbelt and seismic risk.

References

Mann, P. and Corrigan, J.C. (1990). Model for Late Neogene deformation in Panama. Geology, 18, 558-562.

Pindell, J.L. (1993). Regional synopsis of Gulf of Mexico and Caribbean evolution. In: Pindell, J.L. and Perkins, R.F. (eds) Transactions of the 13th Annual GCSSEPM Research Conference: Mesozoic and Early Cenozoic Development of the Gulf of Mexico and Caribbean Region, 251-274.

Trenkamp, R., Kellogg, J.N., Freymueller, J.T. and Mora, H.P. (2002). Wide plate margin deformation, southern Central America and northwestern South America, CASA GPS observations. Journal of South American Earth Sciences, 15, 157-171.

Wadge, G. and Burke, K. (1983). Neogene Caribbean Plate rotation and associated Central American tectonic evolution. Tectonics, 2, 633-643.

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Onset and evolution of the western Panamanian volcanic arc: Stratigraphy, tectonic and geochemistry

Corral, I. (1), Griera, A. (1), Gómez-Gras, D. (1), Canals, À. (2), Corbella, M. (1), Vindel, E. (3), Martín-Crespo, T. (4) and Cardellach, E. (1)
(1) Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona) Spain: Isaac.Corral@uab.cat, Albert.Griera@uab.es, David.Gomez@uab.es, Merce.Corbella@uab.es, Esteve.Cardellach@uab.es
(2) Universitat de Barcelona, 08028 Barcelona, Spain: angelscanals@ub.eud 
(3) Universidad Complutense de Madrid, 28040 Madrid, Spain: evindel@geo.ucm.es
(4) Universidad Rey Juan Carlos, 28933 Móstoles (Madrid) Spain: tomas.martin@urjc.es

Panama is located in Southern Central America and constitutes the westernmost part of the Caribbean plate. The geological development of Panama comprises five distinct plate tectonic motions and is directly connected with the subduction of the Nazca plate beneath the Caribbean plate during Cretaceous to Paleogene times. As a result of this subduction a volcanic arc developed on the western margin of the Caribbean plate and migrates to the north during Paleogene to the present day expression in the Cordillera Central in Panama, which is still active. Although the origin of the Caribbean plate seems to begin to be understood (e.g. Hoernle et al., 2002, 2004), the onset of the volcanic arc and its evolution with time and space is still unresolved.

The present work focuses on the tectonostratigraphy of the Panamanian Cretaceous – Paleogene volcanic arc carried out on the Azuero Peninsula, in southwestern Panama. The study is complemented with new geochemical data obtained along the whole arc and in the forearc basin infill sequence, which allows us to infer the geochemical evolution of the volcanic arc in this area.

The main tectonic structures observed in the forearc basin are ENE-WSW trending folds and faults slightly oblique to regional NW-SE tectonic lines. Late minor faults of NW-SE and NE-SW trend have also been observed. These structures were formed as a consequence of the compression produced during the subduction of the Nazca plate under the Caribbean plate and the accretion of sea mounts in front of the subduction trench during Late Cretaceous - Paleogene times.

We have differentiated three major litostratigraphic units, which are, from base to top: (1) basalts, pillow basalts and basaltic dikes, constituting the basement of the arc and corresponding with the CLIP (Caribbean Large Igneous Province); (2) andesites, dacites, volcaniclastic sediments, pelagic limestones and cherts belonging to the Río Quema formation, which represent the infilling sequence of the forearc basin that is interlayed with the volcanic arc rocks developed on the CLIP. Both units are intruded by dyke swarms of basalt to andesite composition; (3) limestones, calcarenites and turbidites belonging to the Tonosí Formation that discordantly overlies the Rio Quema formation.

The basement of the volcanic arc (CLIP) outcrops in the southern part of the Azuero Peninsula and in southern area of the Sona Peninsula. These rocks are tholeiitic character and characterized by low-K differentiation trend in the total alkali-silica diagram (TAS). The trace element and REE patterns display a flat tendency compatible with plateau-like affinities.

The volcanic arc outcrops in the central part of the Azuero Peninsula. The geochemistry of its rocks is characterized by a medium-K differentiation trend in the TAS (i.e. calc-alkaline character). However, two distinct trace elements and REE signatures are recognized in these rocks: (1) basalts, andesites and dacites displaying features characteristics of rocks with volcanic arc affinities (i.e. variably enriched of fluid-mobile elements and depleted of heavy REEs) and (2) basalts with flat REE pattern compatible with oceanic plateau-like affinities and CLIP basement. Even most of plateau-affinities rocks are interpreted older than arc magmatic rocks (Buchs et al., 2007; Buchs, 2008; Wörner et al., 2006, 2009) several dykes with plateau-affinity crosscut both volcaniclastic sediments and arc-type volcanic rocks. This indicates an overlap in time and space of magmas with plateau and arc-affinities and complicates an interpretation based only on a punctual change of mantle source at the onset of the arc magmatism.  

We conclude that the litostratigraphy of the Rio Quema area denote a submarine depositional environment and transpressive/compressive tectonic regime, at least during Cretaceous – Paleogene times. The geochemical data reveals the important role played by the CLIP on the geochemical evolution of the Panamanian Cretaceous – Paleogene volcanic arc, as it overprints the plateau signature in the first stage of the arc evolution and conditions the following stages of the volcanic arc.

References

Buchs, D. M., Baumgartner, P. O., and Arculus, R. J. (2007). Late Cretaceous Arc Initiation on the Edge of an Oceanic Plateau (Southern Central America) Transactions, American Geophysical Union, v. 88, p. Fall meeting Supplement, abstract T13C-1468.

Buchs, D. M. (2008). Late Cretaceous to Eocene geology of the South Central American forearc area (southern Costa Rica and western Panama): initiation and evolution of an intra-oceanic convergent margin. PhD Thesis at “Faculté des geosciences et de l’environnement  de l’Université de Lausanne.

Hoernle, K., Van den Bogaard, P., Werner, R., Lissinna, B., Hauff, F., Alvarado, G., and  Garbe-Schonberg, D. (2002). Missing history (16-71 Ma) of the Galapagos hotspot: Implications for the tectonic and biological evolution of the Americas: Geology, v. 30, p. 795-798.

Hoernle, K., Hauff, F., and van den Bogaard, P. (2004). 70 m.y. history (139-69 Ma) for the Caribbean large igneous province: Geology, v. 32, p. 697-700.

Wörner, G., Harmon, R. S., Wegner, W., and  Singer, G. (2006). Linking America's backbone: Geological development and basement rocks of central Panama.: Abstrstracts with Programs, Geological Society of America, p. 60.

Wörner, G., Harmon, R. S., and Wegner, W. (2009). Geochemical evolution of igneous rocks and changing magma sources during the formation and closure of the Central American land bridge of Panama, Geological Society of America Memoir 204, p. 183-196.

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Developing robust kinematic and mechanical models for complex curved orogens using a multidisciplinary approach: an example from the North American Cordilleran

Arlo Brandon Weil (1) and Adolph Yonkee (2)
(1) Bryn Mawr College Department of Geology, Bryn Mawr College, Bryn Mawr, PA 19010, aweil@brynmawr.edu
(2) Weber State University, Ogden, UT 84408, ayonkee@weber.edu

Most active and ancient mountain belts display map-view curvature over a range of scales, yet mechanisms responsible for developing such curvature remain incompletely understood. Determining the origins of curved mountain belts is critical for understanding the tectonic and paleogeographic evolution of continents. At the root of these problems are when and how mountains acquire curvature during their complex and protracted deformation histories. By integrating structural and paleomagnetic studies throughout the North American Cordillera, we have been able to constrain a 3-D kinematic evolution model and interpret mechanical processes responsible for producing the present-day orogenic architecture. In particular, our focus has been on the Sevier and Laramide belts of Wyoming. These belts are ideal case studies for understanding foreland deformation because there are numerous over-thrusts, basement arches and cover folds with a wide range of trends; abundant seismic and drill hole data that provide key constraints for constructing cross sections and 3-D fold-fault surfaces; measurable patterns of systematic minor layer-parallel shortening and local vertical axis rotations; and excellent exposures of basement and cover rocks that allow analysis of deformation styles and mechanisms over a wide range of structural levels and scales.

Our preliminary tectonic model contends that the Wyoming salient of the Sevier belt began with minor primary curvature, which later underwent progressive secondary rotation penecontemporaneous with mountain building. Rotations are related to curvature of fault slip directions, differential shortening, and wrenching. Processes that gave rise to this kinematic evolution include (i) variations in initial thickness and strength of foreland basin-fill stratigraphy, (ii) feedback with basins that were formed in front of, and eventually incorporated into, the growing mountain belt, and (iii) interaction with foreland uplifts along the salient ends. In contrast, analysis of individual arches and folds in the Wyoming Laramide indicate only minor local rotations during fold and uplift development. In general, declinations from the gently dipping backlimbs of uplifts are consistent with expected paleomagnetic reference directions for Wyoming, whereas declinations along steep frontal limbs show systematic rotations where fold trends curve. Structural and strain analysis in the Laramide show an idealized structural fabric that grades from primary sedimentary fabrics to progressively overprinted weak tectonic fabric. Observed paleomagnetic and strain patterns, when combined with structural relations, are consistent with a hybrid tectonic model for the Laramide of spatial variations in shortening directions likely associated with basement anisotropy, temporal changes in shortening directions, and varying amounts of wrench shear related to changes in structural trend.

Ultimately these tectonic models will be used to test plate-scale geodynamic models for the North American Cordillera during the Late Cretaceous – Paleogene transition from Sevier thins-skinned to Laramide thick-skinned style foreland deformation.

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Palinspastic restoration of bends of the Panamanian Isthmus: Implications for interpretation of bends of orogenic belts

Johnston, Stephen T. (1)
(1) School of Earth & Ocean Sciences, University of Victoria, PO Box 3065  STN CSC, Victoria, British Columbia, Canada V8W 3V6. stj@uvic.ca

How do bent mountain belts form? It is commonly argued that the map-view geometry of an orogen is a reflection of the primary shape of the pre-collisional continental rifted margin.  In this model, the salients and reentrants that characterize the length of an orogen are interpreted as being as being inheritied from primary promontories and embayments that characterized the original passive margin.  For example, the Pennsylvanian and Tennesse salients of the US Appalachians have been explained as the result of wrapping of structures around primary promontories in North America's Iapetan passive margin during collision with Africa (Thomas, 1977, 2006).  Implicit in such a ‘primary’ interpretation is that bends develop through margin-normal displacements.  An alternative interpretation is that highly arcuate orogens originated as more linear features that were subsequently bent, or folded.  Implicit in such a ‘secondary’ interpretation of bent orogens is that bending records margin-parallel translation, and that during bending the orogen moved (sometimes great distances) relative to the adjacent autochthon.  The geometry of the Panamanian Isthmus is consistent with bending of a previously linear orogen in response to margin-parallel translation.  Paleomagnetic data, while sparse, are consistent with relative clockwise and counterclockwise rotations of eastern and western Panama, respectively.  Bending is occurring in the absence of any indenting promontories, and is being accommodated by rotation of Panama out over the Caribbean plate giving rise to the North Panama fold and thrust belt.  Bending can be modeled as the result of folding of a beam (the Panamanian Isthmus) caught between a fixed North American back stop and a northwestward migrating South American block (Silver et al., 1990).  Such a model is consistent with available GPS data (Trenkamp et al., 2002), and with long term Tertiary motion of South American relative to North America (Ladd, 1976).  Assuming 20 mm/a of relative displacement of South America relative to North America (DeMets et al., 1990), the 80 km of shortening required to produce the bends of the Panamanian Isthmus could have been accomplished in 4 Ma.  The amplitude and wavelength of the Panamanian bends are the same as the bends of the Appalachians, leaving open the possibility that the Appalachian bends formed in a similar manner.  The geometry of tight to isoclinals bends of orogenic belts, for example the Alaskan oroclines (Johnston, 2001) of the Cordillera of western North American or the Iberian Orocline of the European Variscides (Gutiérrez-Alonso et al., 2008), preclude interpretation as the result of indentation.  They may instead represent the end products of continued bending of ribbon continents in a fashion similar to that of the Panamanian Isthmus.

References

DeMets, C., Gordon, R.G., Argus, D.F., and Stein, S., 1990, Current plate motion: Geophysical Journal International, v. 101, p. 425-478.

Gutiérrez-Alonso, G., Fernández-Suárez, J., Weil, A.B., Murphy, J.B., Nance, R.D., Corfu, F., and Johnston, S.T., 2008, Self-subduction of the Pangaean global plate: Nature Geoscience, v. 1, p. 549-553.

Johnston, S.T., 2001, The Great Alaskan Terrane Wreck: Reconciliation of paleomagnetic and geological data in the northern Cordillera: Earth and Planetary Science Letters, v. 193, p. 259-272.

Ladd, J.W., 1976, Relative motion of South America with respect to North America and Caribbean tectonics: Geological Society of America Bulletin, v. 87, p. 969-976.

Silver, E.A., Reed, D.L., Tagudin, J.E., and Heil, D.J., 1990, Implications of the North and South Panama Thrust Belts for the Origin of the Panama Orocline: Tectonics, v. 9, p. 261-281.

Thomas, W.A., 1977, Evolution of Appalachian-Ouachita salients and recesses from reentrants and promontories in the continental margin: American Journal of Science, v. 277, p. 1233-1278.

—, 2006, Tectonic inheritance at a continental margin: GSA Today, v. 16, p. 4-11.

Trenkamp, R., Kellogg, J.N., Freymueller, J.T., and Mora, H.P., 2002, Wide plate margin deformation, southern Central America and northwestern South America, CASA GPS observations: Journal of South American Earth Sciences, v. 15, p. 157-171.

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Canal Zone volcanic rocks and the tectonic evolution of the Panama arc

David W. Farris(1), Agustin Cardona(2), Camilo Montes(2)
1. Florida State University, Tallahassee, Florida
2. Smithsonian Tropical Research Institute, Panama City, Panama

The volcanic rocks of the Panama Canal Culebra Cut lie at an inflection point in the tectonic evolution of the Panama arc. The southern Panama Canal exposes a sequence of Oligocene through Miocene volcanic rocks and volcaniclastic sedimentary basins, however the below changes pertain to volcanic rocks throughout Panama.  Oligocene Bas Obispo Formation and older rocks exhibit relatively stable geochemical characteristics, low Ta/Yb ratios suggesting a strong slab signature, and low La/Yb ratios indicative of thin island arc crust.  Miocene Las Cascadas Formation (23 Ma) and younger volcanic rocks exhibit increasingly continental characteristics suggestive of lessening slab influence (e.g. continuously increasing Ta/Yb and La/Yb ratios).  This change is not gradual, but is instead a sharp inflection point characteristic of a discrete tectonic change.

Within the southern Canal Zone, the youngest volcanic unit is colloquially termed the Late basalt.  The Late basalt unit sits conformably on top of and intrudes through the 17 Ma and younger Pedro Miguel Formation pyroclastic rocks.  The Late basalt and Pedro Miguel Formation are arc tholeiites, but exhibit a trend toward MORB-like characteristics including flat REE’s, high Ti, high V/Ti, and low K/Yb ratios.  These anomalous trends can potentially be explained by temporally similar extension localized within the Canal Zone.

The Canal Zone contains a complex sequence of normal and strike-slip faults, which can help explain changes in arc activity.  Cross-cutting relations suggest that normal faulting occurred first, followed by strike-slip faults that remain active today.  Often this change in motion occurred along a single fault plane as can be observed by perpendicular sets of slicken-sides on a particular fault surface.  One explanation of Canal Zone geochemical data is a period of extension, which produced the Las-Cascadas through Late basalt units followed by on going crustal thickening throughout Panama.  A likely driver of this process is the initiation and on-going collision of the Panama block with South America. In this model, initial collision caused the isthmus to fracture along the Canal Zone, producing localized extension and depleted arc magmatism, but ongoing collision yielded thickened arc crust and a more continental signature throughout the Panama arc.

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Arc initiation and margin development in South Central America

David Buchs (1), Peter Baumgartner (2), Richard Arculus (1), Claudia Baumgartner(2)
(1) Research School of Earth Sciences, Australian National University
(2) Institute of Geology and Paleontology, University of Lausanne, Switzerland

A new tectono-stratigraphic subdivision of the forearc area between southern Costa Rica and western Panama has been defined, which provides an insight into the development of the South Central American Margin. Our results integrate 10 months of field work, new biochronologic dating, geochemical data of 192 igneous rocks and structural observations based on satellite images. We subdivided the basement of the studied area into 6 oceanic complexes that are locally covered by forearc sediments (Buchs, 2008; Buchs et al., 2009; other papers in review).

The Golfito Complex (S Costa Rica) includes three tectono-stratigraphic units that are broadly composed of late Campanian to Eocene volcano-sedimentary deposits. Some lava flows at the base of the complex belong to a late Cretaceous oceanic plateau named herein “Azuero Plateau”, which forms the basement of the South Central American Arc. Other lavas flows at the base of the complex represent proto-arc lava that emplaced on top of the plateau during the late Campanian.

The Osa Igneous Complex (S Costa Rica) occurs along the outer side of the Golfito Complex and has been subdivided into the Inner Osa Igneous Complex and Outer Osa Igneous Complex. The Inner Osa Igneous Complex is composed of an oceanic plateau that formed in the Pacific during the Coniacian-Santonian and accreted along the margin in the Paleocene. The Outer Osa Igneous Complex includes an imbricate of Coniacian-Santonian to middle Eocene seamounts that accreted along the margin between the Paleocene and the middle Eocene.

The Osa Mélange (S Costa Rica) is in contact with the Osa Igneous Complex and forms the outermost parts of the margin. It is composed of three units. The innermost unit comprises accreted sediments that were produced by mass-wasting in the late Eocene. The sediments are made of reworked sediments and igneous igneous rocks from the forearc slope, the volcanic arc and the formerly accreted Osa Igneous Complex. The outermost units of the Osa Mélange are composed of hemipelagic sediments that accreted along the margin between the Oligocene and the Miocene.

The Azuero Marginal Complex (W Panama) is mostly composed of three units. The Azuero Plateau occurs in the lower part of the complex. It is made of a Coniacian-early Santonian oceanic plateau that forms the basement of the South Central American Arc and also occurs in the Golfito Complex. The Azuero Proto-arc Group is another unit that locally caps or intrudes the Azuero Plateau and is composed of igneous rocks with primitive island arc affinities. The proto-arc igneous rocks are locally interlayered with late Campanian hemipelagic limestones of the Ocú Formation. Finally, the uppermost parts of the Azuero Marginal Complex consist of the Azuero Arc Group that rests on top of the Azuero Plateau and Azuero Proto-arc Group. The Azuero Arc Group is composed of Maastrichtian to Eocene volcano-sedimentary deposits and related intrusives that belong to the early South Central American Volcanic Arc (Lissinna, 2005; Wörner et al., 2009).

The Azuero Mélange (W Panama) is a subduction related mélange intercalated between the Azuero Marginal Complex and the Azuero Accretionary Complex (see below). The mélange formed in the middle Eocene as a response to subduction of Maastrichtian seamounts and may also reflects erosion of the margin by seamount tunnelling.

Finally, the Azuero Accretionary Complex (W Panama) occurs along the outer side of the Azuero Mélange. It is composed of Paleocene to early Eocene oceanic islands that accreted along the margin in the middle Eocene.

The definition and characterization of above complexes provide results of major significance for our understanding of the evolution of the Middle American Margin. First, we provide direct evidences that the basement of the South Central American Arc is composed of a late Cretaceous oceanic plateau defined here as the “Azuero Plateau”. This oceanic plateau probably extends in the Caribbean Basin and is part of the Caribbean Large Igneous Province. Second, we identified proto-arc igneous rocks of the South Central American Arc along a ~450 km-long margin segment. These rocks emplaced within and on top of the Azuero Plateau during the late Campanian (~75-73 Ma) and may extend toward eastern Panama. They have atypical geochemical affinities with compositions intermediate between oceanic plateaus and island arcs, which we interpret to reflect their unusual setting of emplacement. Finally, recognition of new oceanic complexes and our tectono-stratigraphic data indicate that the evolution of the outer margin occurred through episodic accretion and subduction erosion. Based on the geologic record we propose that, although the Middle American Margin is generally regarded as a typical example of an erosive margin (e.g. Ranero and von Huene, 2000), accretion of seamounts may currently be active.

References

Buchs, D. M. (2008), Late Cretaceous to Eocene geology of the South Central American forearc area (southern Costa Rica and western Panama): Initiation and evolution of an intra-oceanic convergent margin, PhD thesis, 238 p., Université de Lausanne, Switzerland.

Buchs, D. M., P. O. Baumgartner, C. Baumgartner-Mora, A. N. Bandini, S.-J. Jackett, M.-O. Diserens, and J. Stucki (2009), Late Cretaceous to Miocene Seamount Accretion and Mélange Formation in the Osa and Burica Peninsulas (Southern Costa Rica): Episodic Growth of a Convergent Margin, in Geology of the area between North and South America, with focus on the origin of the Caribbean Plate, edited by K. James, M. A. Lorente and J. Pindell, 411-456.

Lissinna, B. (2005), A profile though the Central American Landbridge in western Panama: 115 Ma Interplay between the Galápagos Hotspot and the Central American Subduction Zone, PhD thesis, 102 p., Christian-Albrechts University, Kiel, Germany.

Ranero, C. R., and R. von Huene (2000), Subduction erosion along the Middle America convergent margin, Nature, 404, 748-755.

Wörner, G., R. S. Harmon, and W. Wegner (2009), Geochemical Evolution of igneous rock and changing Magma Sources during the Evolution and Closure of the Central American Landbridge, in Backbone of the Americas, edited by S. Mahlburg Kay and V. Ramos, 183-196.

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Jurassic-Cretaceous accretion-subduction records in the Caribbean Plate North of the CLIP (Nicaragua, Costa Rica)

Peter O. Baumgartner (1), Kennet Flores, Alexandre Bandini, Claudia Baumgartner-Mora(1), David Buchs(2)
(1)(2) Institute of Geology and Paleontology, University of Lausanne, Switzerland
(2) Research School of Earth Sciences, Australian National University

Today, a SW-NE trending strike slip fault zone running SE of the Nicoya Peninsula (Costa Rica) and possibly connecting with the Hess Escarpment, separates two major basement domains of the Caribbean Plate: To the NW, oceanic/arc basements range in age from Late Triassic to Early Cretaceous and form a complicated puzzle of geodynamic units discussed here in more detail. To the SE of this fault line, no Jurassic radiolarite, no sediment age older than Turonian-Santonian, and with few exceptions, no 40Ar/39Ar - basement age older than 90 Ma is known, all the way to Colombia. For us, this area only represents the trailing edge of the CLIP.

Our new sudivision of geodynamic units is based on: Late Triassic to Tertiary radiolarian and foraminiferan biochronology of ribbon radiolarites and limestones, igneous geochemistry and  40Ar/39Ar-ages, and detailed field work in selected areas such as: Siuna, El Castillo (Nicaragua), Santa Elena, the Gulf of Nicoya, Herradura, Quepos, Osa, Golfito, Burica (Costa Rica), Coiba, Sona, and Azuero (Panama).

The Mesquito Composite Oceanic Terrane (MCOT) comprises the southern half of the Chortis Block, classically assumed to be a continental fragment of N-America. The MCOT is defined by 4 corner localities characterized by ultramafic and mafic oceanic and arc rocks and radiolarites of Late Triassic, Jurassic and Early Cretaceous age:

1. The Siuna Serpentinite Mélange (NE-Nicaragua) contains, high pressure metamorphic mafics and Middle Jurassic (Bajocian-Bathonian) radiolarites in original, sedimentary contact with arc-metandesites. The Siuna Mélange also contains Late Jurassic black detrital chert formed in a marginal (fore-arc?) basin shortly before subduction. A phengite 40Ar/39Ar -cooling age dates the exhumation of the high pressure rocks as 139 Ma (earliest Cretaceous). We interpret the Suina Mélange as the result of a collision and partial subduction Jurassic oceanic island arc with the Agua Fria arc system (Chortis Block s. str.), that represented a piece of the N-American active continental margin.

2. The El Castillo Mélange (S-Nicaragua/N- Costa Rica) comprises a radiolarite block tectonically embedded in serpentinite and alkaline metabasalts that yielded a diverse Rhaetian (latest Triassic) radiolarian assemblage, the oldest fossils recovered so far from S-Central America. We interpret this mélange as part of a large ultramafic accretionary complex that represents the basement of much of Nicaragua underneath the Late Cretaceous to Tertiary arc systems.

3. The Santa Elena Ultramafics (N-Costa Rica) together with the serpentinite outcrops near El Castillo (2), are the southernmost outcrops of the MCOT. The Santa Elena Unit (3) itself is still undated, but it is thrust onto the middle Cretaceous Santa Rosa Accretionary Complex (SRAC), that contains, according to our most recent findings, extended radiolarite series of Early Jurassic age associated with alkaline sills and km-thick alkaline basalt units. MOR-type basalts are associated with Middle Jurassic to Early Cretaceous radiolarites.

All this material could either be reworked from the MCOT, which was the upper plate with respect to the SRAC, or represents another Jurassic oceanic setting accreted into the middle Cretaceous SRAC.

4. Serpentinites, metagabbros and basalts have long been known from DSDP Leg 67/84, drilled off Guatemala in the Nicaragua-Guatemala forearc basement. They have been restudied and reveal 40Ar/39Ar -dated Late Triassic to middle Cretaceous enriched ocean island basalts and Jurassic to Early Cretaceous depleted island arc rocks of Pacific origin.

The MCOT covers most of Nicaragua and could extend to Guatemala to the W and form the Lower (southern) Nicaragua Rise to the NE. Some basement complexes of Jamaica, Hispaniola and Puerto Rico may also belong to the MCOT.

The Nicoya Complex s. str. has been regarded as an example of Caribbean crust and the Caribbean Large Igneous Province (CLIP). However, 40Ar/39Ar -dates on basalts indicate ages as old as Early Cretaceous (139-132 my). Highly deformed Jurassic and Early Cretaceous radiolarites occur as blocks within younger (mostly Late Cretaceous) intrusives and basalts. Our interpretation is that radiolarites became first accreted to the MCOT, then became reworked into the Nicoya Plateau in Cretaceous times. This implies that the Nicoya Plateau formed along the Pacific edge of the MCOT, independent from the CLIP and most probably unrelated with he Galapagos hotspot. Albian ammonites in the Loma Chumico Formation imply the presence of a pre-Albian basement in the eastern Nicoya Peninsula (preliminarily called Matambú Terrane).

Outcrops around the Gulf of Nicoya represent the Manzanillo Terrane characterized by 1. the Tortugual picrites and alkaline basalts  (~90 Ma) that intruded into an unstudied basement. 2. the Berrugate Formation, a Coniacian/Santonian to Early Campanian (~89-80 Ma) forearc sedimentary succession, that was previously confused with the Loma Chumico Formation (see above). The Manzanillo Terrane reflects evolved arc activity that is synchronous with the major CLIP event. It must, therefore, be exotic with respect to the CLIP and the Nicoya Terrane.

To the SE of the S-Nicoya fault line, Turonian-Santonian (~90-85 Ma) oceanic plateaus resting on an unknown basement must represent actual outcrops of the trailing edge of the CLIP. These include the SE corner of the Herradura Promontory (Costa Rica) and the Azuero Plateau cropping out in Coiba, Sona and Azuero (Panama).

Late Campanian to Paleocene arcs rest on the oceanic plateaus ( see Buchs et al. this conference), and are in their early stages geochemically influenced by their basement: The Golfito Complex (Costa Rica) and the Azuero Arc (Panama), possibly also the San Blas Complex (Panama) and the Serrania de Baudo (W-Colombia).

Igneous rocks with plateau and/or seamount affinities that are of late Cretaceous to Eocene age occur outboard of the fore-mentioned units and are exotic with respect to the CLIP. They became accreted during the Early Tertiary:  The Tulin Group (Herradura), Quepos, The Osa Igneous Complex, Burica, the Osa Mélange (Costa Rica/Panama), and the Azuero Accretionary Complex (Panama).

The CLIP formation (~90-85 Ma) on an unknown pacific oceanic crust triggered a new, E-dipping subduction zone and Campanian-Maastrichtian  (~80-70 Ma) initiation of proto-arcs on its trailing edge (see Buchs et al. this conference).

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Late Cretaceous subduction initiation on the southern margin of the Caribbean plateau:  One Great arc of the Caribbean (?)

James E. Wright and Sandra J. Wyld
Department of Geology, University of Georgia, Athens, Ga 30602.  jwright@gly.uga.edu

The stratigraphic, magmatic and structural evolution of Aruba, Curaçao and Bonaire, along with some new U-Pb zircon geochronological results suggests an alternative model for the Late Cretaceous tectonic evolution of the southern Caribbean.  Aruba and Curaçao contain a mafic complex long interpreted as representing exposures of the Caribbean Plateau intruded by ca 89-86 Ma arc related plutons and dikes, whereas the oldest rocks on Bonaire are a volcanic arc sequence that predates plateau formation and the arc plutonic activity on Aruba and Curaçao.  In light of these new data, the Late Cretaceous arc polarity reversal model for the Caribbean due to aborted subduction of the buoyant plateau needs revision.  We suggest that Late Cretaceous subduction initiation along the southern boundary of the plateau generated a Late Cretaceous arc constructed solely on a basement of Caribbean Plateau crust and that this arc is distinct from the Early to Late Cretaceous arc of the Greater Antilles.  The tectonic analysis presented here for Aruba, Curaçao and Bonaire when combined with published data on other late Cretaceous terranes of northwestern South America and the southern Caribbean suggest a geodynamic model involving three separate but temporally overlapping arc systems.

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The role of the Ibero-Armorican Arc development in the tectonic inversion of the South-Portuguese Zone (SW Iberian Massif, Variscan Orogeny)

Pereira, M. Francisco (1), Silva, José, B. (2), Chichorro, M., (3)
(1) Departamento de Geociências, CGE, Universidade de Evora, Portugal, mpereira@uevora.pt
(2) Departamento de Geologia, IDL, Faculdade de Ciências, Universidade de Lisboa, Portugal
(3) CICEGE, Universidade Nova de Lisboa, Portugal

The SW Iberian Massif tells an important part of the history of the late Paleozoic tectonic evolution of northern Gondwana margin, and specially that of the Rheic Ocean. The closure of the Rheic Ocean and consequent continental collision between Gondwana and Laurussia which ultimately led to the amalgamation of Pangea, gave rise to the European Variscan belt (Matte, 2001). The Variscan belt is linear but sinuous with kilometre-scale curvatures.

In Western Europe, the Ibero-Armorican Arc (Ribeiro et al., 1995) includes a fold and thrust belt affecting a foredeep basin in the outer arc (South Portuguese Zone- SPZ), and a fold and thrust belt affecting shallow water continental platform in the inner arc (Cantabrian Zone). These foreland basins are separated by an hinterland (Ossa-Morena Zone, Central-Iberian Zone and West Asturio-Leonese Zone) dominated by Mississipian/early Pennsylvanian high-grade to low-grade metamorphism, synorogenic plutonism and sedimentation, and heterogeneous deformation (Variscan orogeny).

The originally linear Variscan belt was the result of (1) an oblique-subduction process that culminated in the late Devonian (c. 370 Ma) and consequent crustal thickening with subsequent orogenic collapse during the Mississipian/early Pennsylvanian (Tournaisian to early Moscovian; c. 350-310 Ma) (Martinez-Catalan et al., 2007). The orocline formation occurred as a secondary structure in the middle-late Pennsylvanian (late Moscovian to late Gzhelian; c. 306-299 Ma) and was followed by significant late-post-Variscan magmatism (early Permian; c. 295 Ma) (Weill et al., 2010 and references therein).

The geology of SPZ, located in the outer arc, includes a Carboniferous foreland basin and a late Devonian basement characterized by shallow water siliciclastic sediments (Horta da Torre Formation, Represa Formation, PQ Formation and Tercenas Formation) (Oliveira et al., 1990). The Famennian rocks are overlained: (1) by a succession with Tournaisian-Visean felsic volcanism (Volcano-Sedimentary Complex), and late Visean (Mertola Formation) to Serpukovian-Bashkirian (Mira Formation) overlying turbidites, or (2) by a succession of Tournaisian (Bordalete Formation), Visean (Murração Formation) and middle Bashkirian age (Quebradas Formation) mud/carbonate rocks. Lower Bashkirian to late Moscovian (Brejeira Formation) turbidites commonlly rest conformably on Serpukovian-Bashkirian sediments but also unconformably overlie sediments with Tournaisian to Visean ages (Pereira et al., 1994).

As response to middle-late Pennsylvanian tectonic inversion, the overall structure of the SPZ is characterized by southwestward (present coordinates) vergent folding and thrust displacement (Silva et al., 1990). This complex contraction deformation obscured the importance of the Viséan syn-sedimentary gravitational collapse structures and extensional faults. In Mértola we recognized tectonic instability during the late Visean with deposition of thick turbiditic sequences coeval with large-scale slope mass wasting of the older platform margin. The Visean to Moscovian stratigraphy of Aljezur-Bordeira reveals significant lateral changes of sedimentary facies and the presence of unconformities suggesting that sedimentation was influenced by development of synsedimentary extensional faults. The regional folding and thrusting that characterizes the overall structure of the SPZ, with the same age of the Ibero-Armorican Arc development, clearly marks a tectonic inversion that postdated late Visean to late Moscovian deposition contemporaneous with the extensional collapse and significant up-lift and denudation of the Variscan linear orogen (Pereira et al., 2009).

References

Martínez-Catalán, J.R., Arenas, R., Díaz García, F., et al. (2007). Implications for the comprehension of the Variscan belt. In: Hatcher, R.D., Jr, Carlson, M.P., McBride, J.H. & Martínez Catalán, J.R. (eds) 4-D Framework of Continental Crust. Geological Society of America, Memoirs, 200, 403-424.

Matte, Ph. (2001). The Variscan collage and orogeny (480-290 Ma) and the tectonic definition of the Armorica microplate: a review. Terra Nova, 13, 122-128.

Oliveira, J. T. (1990). Stratigraphy and syn-sedimentary tectonism in the South Portuguese Zone, In: Dallmeyer, R.D. and Garcia, E.M., (eds). Pre-Mesozoic Geology of Iberia, Springer, Berlin, 334 – 347

Pereira, M.F., Chichorro, M., Williams, I.S., et al. (2009). Variscan intra-orogenic extensional tectonics in the Ossa-Morena Zone (Évora-Aracena-Lora del Río metamorphic belt, SW Iberian Massif): SHRIMP zircon U-Th-Pb geochronology. Geological Society, London, Special Publications 2009; v. 327; p. 215-237

Pereira, Z., Clayton, G., Oliveira, J.T. (1994). Palynostratigraphy of the Devonian-Carboniferous boundary in Southwest Portugal. Annais Societie Géologique Belgique, 117, 189-199.

Ribeiro, A., Dias, R., Silva, J.B. (1995). Genesis of the Ibero-Armorican arc. Geodinamica Acta, 8, 173-184.

Silva, J.B., Oliveira, J.T. and Ribeiro, A. (1990). Structural outline of the South Portuguese Zone. In: Dallmeyer, R.D. and Garcia, E.M., (eds). Pre-Mesozoic Geology of Iberia, Springer, Berlin, 348–362.

Weil, A., Gutiérrez-Alonso, G., Conan, J. (2010). Arc: a palaeomagnetic study of earliest Permian rocks from Iberia. New time constraints on lithospheric-scale oroclinal bending of the Ibero-Armorican. Journal of the Geological Society,167, 127-143

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Why 307? Absolute age (Ar-Ar and U-Pb) constrains on orocline development and related lithospheric delamination in the Iberian Armorican Arc

Gutiérrez-Alonso, G. (1); Fernández-Suárez, J. (2); Jeffries, T. (3); Collins, A.S. (4); Johnston, S.T. (5); González Clavijo, E. (6), Pastor-Galán, D. (1) and Weil, A.B. (7)
(1) Departamento de Geología, Universidad de Salamanca, Plaza de los Caídos 37008 Salamanca, Spain. gabi@usal.es
(2) Departamento de Petrología y Geoquímica e Instituto de Geología Económica (CSIC), Universidad Complutense, 28040 Madrid, Spain
(3) Department of Mineralogy, The Natural History Museum, London SW7 5BD, UK
(4)  Continental Evolution Research Group, Geology and Geophysics, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
(5) School of Earth & Ocean Sciences, University of Victoria, PO Box 3065 STN CSC, Victoria, British Columbia, Canada V8W 3P6.
(6) Instituto Geológico y Minero de España, Azafranal 48, 37001 Salamanca, Spain
(7) Bryn Mawr College Department of Geology, Bryn Mawr College, Bryn Mawr, PA 19010, U.S.A. aweil@brynmawr.edu

The timeframe for the development of the Ibero-Armorican Arc (West European Variscan Belt), as a bend of a previously more linear orogenic belt, has recently been constrained paleomagnetically as an orocline in the Cantabrian Zone, northern Iberia (the core of the arc)  (Weil et al, 2002, 2010). According to the known evidence, oroclinal generation took place in the uppermost Carboniferous-lowermost Permian, between about 310 and 295 Ma, and it is interpreted to have been ultimately caused by the self-subduction of the Pangean global Plate (Gutiérrez-Alonso et al., 2008). This plate-scale structure is bound to have had a profound effect on the lithosphere and consequently should be recognized in structures developed coevally with the orocline as a consequence of its origin.

One of the most striking features found in the West European Variscan Belt is a large strike-slip shear zone/fault system, characterized as “Late-Variscan”, that runs parallel to broad structural trends around the Iberian Armorican Arc. Ar-40Ar ages in the fabric of 5 shear zones of this system, both dextral and sinestral, have yielded ages that, within error, cluster at 307 Ma, suggesting that their development took place within the time frame of oroclinal bending constrained by paleomagnetism, that is to say, coeval with the formation of the Ibero-Armorican Arc.

In addition, new U-Pb zircon ages for 19 granitoid intrusions of western Iberia, which have also been classically considered as “Late Variscan”, have yielded crystallyzation ages that significantly cluster around 307 Ma (ranging from ca. 309 to 297 Ma) in the outer arc of the orocline, whereas younger granitoid crystallization ages (ca 303-290 Ma) are found in the core of the orocline.

According to our new data and data from the literature, we interpret the development of the strike-slip shear zone system and the origin of the magmatic pulse at ca 307 Ma as being related to orocline development. These new ages constrain deformation in the outer arc to penecontemporaneous with thrust-sheet rotations in the Cantabrian Zone. The 307 Ma strike-slip shear-zones are inferred to have likely accommodated the vertical axis crustal-block rotations needed to accommodate oroclinal bending, while the 307 Ma granitoids in the outer arc represent decompressive melting during the mechanical thinning of the mantle lithosphere below the outer arc during bending. Younger granitoid ages in the inner arc are interpreted to represent orocline triggered lithospheric delamination in the tectonically-thickened inner part of the orocline (Fernández-Suárez et al., 2000; Gutiérrez-Alonso et al., 2004).

References

Fernández-Suárez, J., Dunning, G.R., Jenner, G.A., and Gutiérrez-Alonso, G., (2000). Variscan collisional magmatism and deformation in NW Iberia: constraints from U-Pb geochronology of granitoids. Journal of the Geological Society, 157, 565-576.

Gutierrez-Alonso, G., J. Fernandez-Suarez, and A.B. Weil, (2004). Orocline triggered lithospheric delamination: Geological Society of America Special Paper, 383, 121-131. 

Gutierrez-Alonso, G., Fernandez-Suarez, J., Weil, A.B., Murphy, J.B., Nance, R.D., Corfu, F., and Johnston, S.T., (2008). Self-subduction of the Pangaean global plate. Nature Geoscience, 1, 549-553.

Weil, A.B., van der Voo, R., and van der Pluijm, B.A., (2001), Oroclinal bending and evidence against the Pangea megashear: The Cantabria-Asturias arc (northern Spain): Geology, 29, 991-994.

Weil, A.B., Gutiérrez-Alonso, G., and Conan, J., (2010), New time constraints on lithospheric-scale oroclinal bending of the Ibero-Armorican Arc: a paleomagnetic study of earliest Permian rocks from Iberia: Journal of the Geological Society, London, 167, 127-143.

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Low-temperature Thermochronology in Panama and Western Colombia: Tracing Morphotectonic Response to an Arc-Continent Collisional Event.

Restrepo-Moreno, Sergio A.1,2 Jaramillo, C.1
1 Smithsonian Tropical Research Institute (STRI), Panama
2 Department of Geological Sciences, University of Florid, Gainesville sergiorm@ufl.edu

Recognition of mountain belts as a central product of internal and external geologic processes triggered the advance of important lines of interdisciplinary research[1-10]. As part of this trend a new field known as tectonic geomorphology has emerged,[1] and  geomorphology now plays a pivotal role into understanding how our planet works[5,11]. This new role for geomorphology stemmed from a change in philosophical scope and from advances in relatively new analytical techniques, e.g., low-temperature thermochronology (LTTC), cosmogenic-nuclide analysis, spot analysis of zircon grains, satellite data-imagery, and computer modelling[2,3,5,12-18]. Such techniques are facilitating a new understanding of the interplay between tectonics, climate, and landscape development. For instance, LTTC permits to tackle morphotectonic response of the crust to tectonic and/or climatic input, which in turn allows to define the timing, magnitude and spatial distribution of erosional exhumation and uplift[8, 16, 19, 20]; to reconstruct paleotopography[21]; to quantify long-term erosion rates[8, 22]; to study fault development[23, 24], etc. 

Analysis of low-temperature cooling patterns in mountainous settings of Panama and Western Colombia can provide direct insight into critical morphotectonic processes that may be related to the collision of the Panama-Chocó Block (PCB) with South America. Although scarce, several lines of evidence (e.g., LTTC, paleobotany and sedimentstratigrahy) suggest increased rates of uplift/exhumation for the Northern Andes (Colombia and Venezuela) during the Neogene[8,25-33]. The idea of a major role played by the collision of the PCB in triggering Late Miocene-Pliocene uplift-deformation in the area has also been advanced[17,34,35]. Geographic proximity of the PCB makes this an appealing argument. However, the same recent data indicate that uplift and exhumation for the area is markedly asynchronous so that a number of questions remain still unresolved: What role has the PCB collision played as the driver of major uplift and exhumation in the region? What has been the morphotectonic evolution of the PCB and Western Cordillera of Colombia as the crustal segments proximal to the collision? What effects has morphotectonic response had on landscape and paleogeographic development?

To assess some of the issues introduced above, a high-resolution LTTC study is being carried out by the authors in collaboration with researchers at STRI (Panama), the University of Florida (USA), Universidad Nacional de Colombia (Colombia) and Apatite to Zircon, Inc. (USA). The investigation seeks to unravel the morphotectonic response of mountain ranges in Panama and Western Colombia to the docking of the PCB. The research strategy incorporates LTTC data production, analysis and modelling from samples collected along several vertical and horizontal transects in Western Colombia (Farallones de Citará, Amagá Formation, and Acandí) and Panama (Rio Chagres-Cerro Azul, Azuero, and Cunayala). Zircon characterization (U-Pb age and Hf signatures) will also be accomplished to explore sediment provenance and accumulation patterns. Results of this investigation will shed light on: a) the chronology, extent and spatial distribution of uplift and erosional exhumation, b) the rates of spatially-averaged erosion for the Neogene, c) the patterns of landscape evolution, d) the timing of arc-continent collision, and f) the geodynamic models for orogen and orocline formation.

References

1.   Burbank, D.W., Anderson, R.S., Tectonic Geomorphology. 2001, New York: Blackwell. 274.

2.   Bierman, P.R., Rock to sediment - Slope to sea with Be-10 - Rates of landscape change. Annual Review of Earth and Planetary Sciences, 2004. 32: p. 215-255.

3.  Reiners, P.W., Brandon, M.T., Using thermochronology to understand orogenic erosion. Annual Review of Earth and Planetary Science, 2006. 34: p. 419-466.

4.  Safran, E.B., et al., Erosion rates driven by channel network incision in the Bolivian Andes. Earth Surface Processes and Landforms, 2005. 30(8): p. 1007-1024.

5.  Summerfield, M.A., The changing landscape of geomorphology. Earth Surface Processes and Landforms, 2005. 30: p. 779-781.

6.  Aalto, R., T. Dunne, and J.L. Guyot, Geomorphic controls on Andean denudation rates. The Journal of Geology, 2006. 114: p. 85-99.

7.  Bishop, P., Long-term landscape evolution: linking tectonics and surface processes. Earth Surface Processes and Landforms, 2007. 32(3): p. 329-365.

8.  Restrepo-Moreno, S.A., et al., Long-term erosion and exhumation of the "Altiplano Antioqueño", Northern Andes (Colombia) from apatite (U-Th)/He thermochronology. Earth and Planetary Science Letters, 2009. 278(1-2): p. 1-12.

9.   Montgomery, D.R., G. Balco, and S.D. Willett, Climate, tectonics, and the morphology of the Andes. Geology, 2001. 29(7): p. 579-582.

10. Vasconcelos, P.M., et al., Geochronology of the Australian Cenozoic: a history of tectonic and igneous activity, weathering, erosion, and sedimentation. Australian Journal of Earth Sciences, 2008. 55(6-7): p. 865-914.

11. Leopold, L.B., Geomorphology: A sliver off the corpus of science. Annual Review of Earth and Planetary Sciences, 2004. 32: p. 1-12.

12. Willgoose, G., Mathematical modelling of whole landscape evolution. Annual Review of Earth and Planetary Sciece, 2005. 33: p. 443–59.

13. Whipple, K.X. and B.J. Meade, Orogen response to changes in climatic and tectonic forcing. Earth and Planetary Science Letters, 2006. 243(1-2): p. 218-228.

14. Jackson, S.E., et al., The application of laser ablation microprobe (LAM)-ICP-MS to in situ U–Pb zircon geochronology. V.M., Goldschmidt Conference, Journal Conference Abstract 1996. 1: p. 283.

15. Ketcham, R.A., Forward and inverse modelling of low-temperature  thermochronometry data. Reviews in Mineralogy and Geochemistry, 2005. 48: p. 275-314.

16. Farley, K.A., (U-Th)/He dating: techniques, calibrations, and applications. Reviews in Mineralogy and Geochemistry, 2002. 47: p. 819-844.

17. Trenkamp, R., et al., Wide plate margin deformation, southern Central America and northwestern South America, CASA GPS observations. Journal of South American Earth Sciences, 2002. 15(2): p. 157-171.

18. Donelick, R.A., O'Sullivan, P.B., Ketcham, R.A., Apatite fission-track analysis, in Low-temperature thermochronology: techniques, interpretations, and applications, Reviews in Mineralogy and Geochemistry, P.W. Reiners, Ehlers,  T.A., Editor. 2005, MSA: Chantilly, VA. p. 49–94.

19. Flowers, R.M., S.A. Bowring, and P.W. Reiners, Low long-term erosion rates and extreme continental stability documented by ancient (U-Th)/He dates. Geology 2006. 34(11): p. 925-928.

20. Foster, D.A., A.J.W. Gleadow, G. Mortimer, Rapid Pliocene exhumation in the Karakoram (Pakistan) revealed by fission-track thermochronology of the K2 gneiss. Geology, 1994. 22: p. 19-22.

21. House, M.A., Wernicke, B.P., Farley, K. A. , Paleo-geomorphology of the Sierra Nevada, California, from (U-Th)/ He ages in apatite. American Journal of Science 2001. 301: p. 77-102.

22. Gunnell, Y., Present, past and potential denudation rates: is there a link? Tentative evidence from fission-track data, river sediment loads and terrain analysis in the South Indian shield. Geomorphology 1998. 25: p. 135-153.

23. Stockli, D.F., K.A. Farley, and T.A. Dimitru, Calibration of the apatite (U-Th)/He thermochronometer on an exhumed fault block, White Mountains, California. Geology, 2000. 28(11): p. 983-986.

24. Ehlers, T.A. and K.A. Farley, Apatite (U-Th)/He thermochronometry: methods and applications to problems in tectonic and surface processes. Earth and Planetary Science Letters, 2003. 206: p. 1-14.

25. Kohn, B.R., et al., Mesozoic-Pleistocene fission-track ages on rocks of the Venezuelan Andes and their tectonic implications. In The Caribbean-South American plate boundary and regional tectonics, GSA Memoir, Bonini, Hargraves, and Shagam, Editors. 1984, GSA: Boulder, CO. p. 365-384.

26. Kroonenberg, S.B., J.G.M. Bakker, and A.M. Van der Wiel, Late Cenozoic uplift and paleogeography of the Colombian Andes - constraints on the development of high-Andean biota. Geologie en Mijnbouw, 1990. 69(3): p. 279-290.

27. Van der Hammen, T., Late Cretaceous and Tertiary stratigraphy and tectogenesis of the Colombian Andes. Geologie en Mijnbouw, 1961. 40: p. 181-188.

28. Hooghiemstra, H., Vegetational and climatic history of the high plain of Bogotá, Colombia. Dissertationes Botanicae. Vol. 79. 1984, Vaduz: J. Cramer. 368.

29. Gregory-Wodzicki, K.M., Uplift history of the central and northern Andes: a review. GSA Bulletin, 2000. 112: p. 1091-1105.

30. Mora, A., et al., Climatic forcing of asymmetric orogenic evolution in the Eastern Cordillera of Colombia. GSA Bulletin, 2008. 120(7-8): p. 930-949.

31. Cardona, A., et al., Transient Cenozoic tectonic stages in the southern margin of the Caribbean plate: U-Th/He thermochronological constraints from Paleogene plutonic rocks in the Santa Marta Massif and Jarara Serranía, Colombia. Special Volume Subduction Zones in the Caribbean, In preparation: p. 1-54.

32. Restrepo-Moreno, S.A., et al., What do Sedimentary Provenance Analysis, Low-Temperature Thermochronology and Paleobotany Say About Uplift and Exhumation Histories of the Amagá Formation (Colombia)? Journal of South America Earth Sciences, In preparation.

33. Hernández, O. and J.M. Jaramillo, Reconstrucción de La Historia Termal en los Sectores de Luruaco y Cerro Cansona (Cuenca del Sinú-San Jacinto) y en el Piedemonte Occidental de la Serranía del Perijá Entre Codazzi y La Jagua e Ibirico (Cuenca del Cesar-Ranchería). 2009, Agencia Nacional de Hidrocarburos - Universidad Nacoinal de Colombia: Bogotá, Colombia. p. 85.

34. Coates, A.G., et al., The geology of the Darien, Panama, and the late Miocene-Pliocene collision of the Panama arc with northwestern South America. GSA Bulletin, 2004. 116(11/12): p. 1327-1344.

35. Suter, F., et al., Structural imprints at the front of the Chocó-Panamá indenter: Field data from the North Cauca Valley Basin, Central Colombia Tectonophysics, 2008. 460(1-4): p. 134-157

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Neogene vulcanism in the southwestern South Caribbean deformed belt: preliminary data from the Sinu belt, Colombia

Cardona, A.(1),  Weber, M. (2), Cerón, J. (3), Espitia, D.(3), De la Parra, F. (3), Lara, M. (2), Montes, C. (1), Toro, M. I. (4), Valencia, V. (5), Bustamante, C (1), Ibañez, M. (6)
(1) Smithsonian Tropical Research Institute, Panamá
(2) Departamento de Geociéncias y Medio Ambiente, Universidad Nacional, Medellín, Colombia
(3) Empresa Colombiana de Petróleos (ECOPETROL), Colombia
(4) Universidad de Córdoba, Montería, Colombia.
(5) VALENCIA GEOSERVICES, Tucson, Arizona, USA.
(6) Department of Geosciences, University of Arizona, USA

The South Caribbean deformed belt is the post-Eocene accretionary wedge that records sedimentation and deformation due to South American and Caribbean convergence (Case et al., 1984). In northern Colombia its onshore exposure is known as the Sinu Belt (Duque-Caro, 1979, Toto and Kellog, 1991). This belt includes Oligo-Miocene shales and Upper Miocene to Pleistocene Turbidites, as well as several mud diapirs. Two outcrops of basaltic andestic dykes intruding Miocene sediments were recently recognized. New geochemical and geochronological data is been obtained to test the origin and tectonic implications of this vulcanism within the Miocene Caribbean tectonics. Three potential petrotectonic models are test: (1) oceanic plate lithospheric fracture in response to plate flexure during subduction, (2) transtensional related tectonics, (3) initiation of a frontal subduction. Preliminary analysis suggest that model (2) is a coherent tectonic scenario.This event correlates with contemporaneous extensional magmatism in the Falcon Basin (Muessig, 1984) within the Venezuelan margin, and is a reflect of the eastern escape of the southern boundary of the Caribbean margin.

References

Case. J., Holcombe.T.L., Martin.R.G., 1984. Map of geologic provinces in the Caribbean region. Geological Society of America, Memoir162, p.1-31

Duque-Caro, H., 1979. Major structural elements and evolution of northwestern Colombia. In: Geological and Geophysical Investigations of Continental Margins (edited by J. S. Watkins, L. Montadeft, and P. W. Dickersen). American Association of Petroleum Geologists, Memoir 29, 329-351.

Muessig, K. W., 1978. The central Falcón igneous suite, Venezuela: alkaline basaltic intrusions of Oligocene-Miocene age. Geologie en Mijnbouw. 57, 261-266

Toto, E. A., Kellogg, J. N., 1991. Structure of the Sinu-San Jacinto fold belt - An activeaccretionary prism in northern Colombia. Journal of South American Earth Sciences. 5, 211-222.

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Metallogenesis and Arc Evolution of Panama and NW Colombia

Redwood, Stewart D.
Consulting Economic Geologist, PO Box 0832-1784, World Trade Center, Panama, Panama.
mail@sredwood.com. www.sredwood.com

Panama and NW Colombia have a rich endowment of copper and gold deposits which formed as a result of subduction-related arc magmatism and are an integral part of arc formation. Metallogenesis – the distribution of mineral deposits in space and time – can contribute to the understanding of the evolution of magmatic arcs and terranes. The reverse is also true, and plate tectonic models are an important aid in selection of prospective areas for mineral exploration. This paper describes the distribution of porphyry copper and/or gold, and epithermal gold deposits of the Pacific arcs and terranes of Panama and NW Colombia. Arc-related mineral deposits can be classified as either 1) pre-collisional (allochthonous), i.e. deposits which formed in the arc terrane and were transported with the terrane to become accreted in their present location, and 2) post-collisional (autochthonous), i.e. deposits which formed after terrane accretion on basement of older terranes, and may cross terrane boundaries, and are related to younger, subduction-related magmatism.

The copper-gold deposits of western Panama, part of the Chorotega Block, are described first, in order of decreasing age, followed by those of eastern Panama and NW Colombia. The two zones have distinctive geology and are separated by the Panama Canal zone, which some models interpret to be a fault with sinistral offset.

Western Panama appears to show a trend of northward-migrating arc magmatism and mineralization:

1. South Azuero Gold Belt. This is a magmatic arc of Late Cretaceous to Paleocene age at the southern end of the Azuero Peninsula, with high sulfidation epithermal gold deposits at Cerro Quema (0.5 million ounces (Moz) Au), Pitaloza and other showings associated with extensive zones of advanced argillic alteration. The occurrence of shallow epithermal systems in such old rocks is very unusual and requires unusual conditions of preservation, such as burial, the reasons for which are not evident in Azuero.

2. North Azuero Gold Belt. This is a poorly defined Eocene arc in the northern part of the Azuero and Soná Peninsulas with showings of epithermal gold mineralization.

3. Petaquilla Copper-Gold Belt. This belt is of Oligocene age and is located in an un-explained position on the north side of the Central Cordillera, and may form the earliest part of the Neogene Central Cordillera arc, although it would be expected to be located on the southern side of the Cordillera in a model of northward arc migration. This belt contains a cluster of large porphyry copper-molybdenum deposits of Petaquilla (5.6 million tonnes (Mt) Cu), surrounded by low to intermediate sulfidation epithermal gold mineralization, including the Molejon deposit (0.9 Moz Au).

4. Central Cordillera Copper-Gold Belt. The Central Cordillera of western Panama is a young, autochthonous, subduction-related volcanic arc of Miocene to Quaternary age. It hosts epithermal gold deposits in the eastern part of intermediate sulfidation epithermal breccias (Santa Rosa, 1.0 Moz Au) and veins (Remance, 0.5 Moz Au; Veraguas gold district; Cacao; Capira) and high sulfidation epithermal deposits (Rio Liri, 0.07 Moz Au; Zioro). The western part of the belt has major porphyry copper-molybdenum deposits including Cerro Colorado (11.5 Mt Cu) and Cerro Chorcha (1.0 Mt Cu, 0.45 Moz Au) in Panama, and Sukut, Rio Nari, Nimaso and others in Costa Rica. The zonation of the distribution of mineral deposits from epithermal gold in the east to porphyry copper in the west is related to plate tectonics, with collision of the oceanic Cocos Ridge with the subduction zone in western Panama and eastern Costa Rica resulting in uplift with higher topographic elevations to +3,000 m and deeper erosion to expose the deeper parts of the hydrothermal systems.

Eastern Panama and NW Colombia are formed by a series of poorly defined accreted arc and oceanic terranes, with copper-gold mineralization related to pre- and post-accretion arcs:

1. Mandé-Acandí-San Blas Copper-Gold Belt. This is an allochthonous island arc with Paleocene-Eocene age magmatism which forms part of the Cañas Gordas terrane that was accreted to the northern Andes in the Miocene, although the timing is poorly constrained. The arc hosts poorly explored porphyry copper-gold deposits including, from south to north, Andagueda, Pantanos-Pedagorcito, Murindó and Acandí in Colombia, and Rio Pito and other showings in the Darien Mountains of San Blas in eastern Panama. There are major alluvial gold deposits (+10 Moz Au) derived from the arc in the Choco basin on the western side of the belt, which continue into the Chucunaque Basin of Panama. Alluvial platinum in these basins is probably derived from Alaskan-type zoned ultramafic-mafic intrusions, such as Alto Condoto, that are exposed in the deeply eroded roots of the arc.

2. Baudo – Majé (Choco) Copper-Gold Belt. The Baudo terrane of the Choco of NW Colombia and southern Darien of Panama is formed of Late Cretaceous to Paleogene ocean plateau basalts and sediments and was accreted to NW Colombia in the Late Miocene. The terrane also contains arc volcanic and intrusive rocks of unknown age (possibly Eocene or Oligocene) which host porphyry copper mineralization (Ipeti-Guayabo, Serranía de Majé), epithermal gold (Mogue) and intermediate sulfidation epithermal gold in breccia pipes and veins (Espiritu Santo de Cana, +2 Moz gold) in Panama. The latter deposit was Panama’s largest historical gold producer. In addition, there is widespread alluvial gold in the belt.

3. Middle Cauca Gold Belt. This belt is of Upper Miocene to Pliocene age and extends from north of Medellin to Ibague in the Western and Central Cordilleras. It is a post-collisional autochthonous arc related to subduction of the Nazca Plate, following a gap in Neogene volcanism in eastern Panama and northern Colombia. The belt is emplaced in the Romeral Terrane and extends into the western edge of the craton. The belt has a very strong gold endowment and hosts at least two world class gold deposits with over 10 Moz gold, Marmato and La Colosa. This belt is characterized by porphyry gold deposits (Titiribi, 4.8 Moz Au and 0.7 Mt Cu; La Mina; Quebradona; Quinchia, +3 Moz Au;  La Colosa, 13 Moz Au), intermediate-sulfidation epithermal gold deposits (Zancudo; Marmato, +10 Moz Au), and breccia pipes (Buritica, Miraflores) hosted by porphyry stocks. Magmatism and mineralization formed in a sinistral transtensional setting interpreted to be related to the oblique collision of the Choco-Panama terrane. The style of mineralization of porphyry gold deposits, which tend to form at a shallower level than porphyry copper-molybdenum deposits, intermediate sulfidation epithermal to mesothermal deposits, and absence of lithocaps and high sulfidation epithermal gold deposits is considered to be related to tectonic and climatic factors, including the transtensional setting giving rise to high-level intrusion of large stocks, rapid mountain uplift due to on-going collision, and high rainfall and erosion.

Many aspects of the metallogenesis, arc evolution and tectonics of Panama and NW Colombia are still poorly understood, and some outstanding questions on the distribution of mineral deposits include:

1. The preservation of high sulfidation epithermal deposits in the Late Cretaceous to Paleocene South Azuero arc.

2. The enigmatic position of the Petaquilla deposits on the north side of the Central Cordillera Miocene to Quaternary arc.

3. The relationship of mineral belts and arcs between western and eastern Panama across the Canal zone.

4. The discrepancy in age of accretion of the Paleocene-Eocene deposits of the Mandé-Acandí-San Blas between Northern Andean models, which place accretion in the Oligocene, and Panamanian models which place accretion in the Miocene.

5. The age of mineralization and arc magmatism of the Baudo-Majé arc.

Additional study of the plate tectonic evolution and mineral deposits of the region will enable these questions to be addressed and the metallogenic models to be refined.

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Vertical axis rotations and latitudinal translations of the Panama orocline

Silva C.(1,2), Bayona G.(1,2), Channell J.E.T.(3), Osorio A.(1), Montes C.(1,2) &
Jaramillo C.(1)
(1) Smithsonian Tropical Research Institution, Ancon, Panama,
(2) Corporación Ares, Colombia
(3) Department of Geological Sciences, University of Florida, USA

From 50 paleomagnetic sites we isolated reliable components of 25 sites that were sampled in Paleocene to Pleistocene volcanic rocks along Panama. These 25 sites are distributed in five areas: Colon, Mamoni, Terable with Upper Cretaceous to Oligocene basaltic rocks; El Valle with Late Miocene to Pleistocene volcanic rocks and Canal with Middle Miocene volcano-sedimentary rocks. Seven components were isolated; components 'ne' (D 51.5, I -12.7, k 23.84, α95 3.7, n 9) and 'w' (D 289.1, I -13.8, k 19.97, α95 6.5, n 3), isolated in the pre-Tertiary ocean basaltic rocks, uncovered the vertical axis due to the Río Gatún sinistral fault. Components 'n' (D 351.3, I 13.7, k 73.47, α95 6, n 1) and 'r' (D 174.2, I -12.6, k 78.54, α95 6.9, n 1) indicate normal and reverse of a recent magnetic field recorded in tuffs and breccias of El Valle volcano (≤ 7 Ma). Component 'b' (D 264.6, I 5.3, k 292.35, α95 3.5, n 1) is a counter clockwise rotated direction of a younger dike (Miocene?) cutting through the pre-Tertiary ocean basaltic rocks; component 'a' indicate a non rotated normal magnetic field of an Oligocene site (D 346.7, I 13.1, k 20.73, α95 12.5, n 1) and component 's' was isolated only in the Canal showing southerly direction.

Clockwise and counter clockwise vertical axis rotation have been uncovered along the Panama orocline in components 'ne' and 'w'. These rotations are linked to a sinistral fault (Río Gatún) that show a counter clockwise rotation of 58º ± 14º at the northern block and clockwise rotation of 65º ± 13º at the southern block.

An average inclination from components 'ne' and 'w', except one dike site, (I -11.9, k 185.91, α95 3.4, n 11, R 10.95) indicate a paleolatitude of the Panama Isthmus of 6ºS ± 3.4 during the Paleocene. Paleolatitudes measured in Oligocene to Pleistocene components ('a', 'n' and 'r') indicate a north latitude of the Isthmus (~7ºN), close to its present location.

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last modified: 02.18.10 16:15 +0100