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 Volume 2 Chapter 5

Chapter  5

Jurassic Evolution of the Northwestern Corner of Gondwana: Present Knowledge and Future Challenges in Studying Colombian Jurassic Rocks

By Germán BAYONA, Camilo BUSTAMANTE, Giovanny NOVA and Ana Milena SALAZAR–FRANCO

Pages 101–132

Manuscript accepted October 29, 2018


Abstract 


This paper summarizes actual knowledge of metamorphic, plutonic, volcanic, carbonate and clastic sedimentary Jurassic rocks that are exposed from northern Perú to Venezuela. This compilation allows an evaluation of three tectonic models that have been proposed for the evolution of the northwestern corner of Gondwana: An extensional model, a subduction–dominated model, and the along–marginal migration of blocks model, that last of which considers the interaction of western subduction and the north–south separation of continental blocks. We conclude that (i) the Jurassic evolution of this orthogonal margin cannot be represented in a single paleogeographic map that represents a dominant geodynamic process; (ii) future analyses must consider the superposition of both Pacific subduction and proto–Caribbean extensional processes; (iii) extensional basins in Guajira, the Perijá range and the Mérida Andes include the sedimentary record of predominantly proto–Caribbean extension, whereas western–subduction processes are recorded by a batholith chain that extends from southern Ecuador to the Santa Marta Massif; and (iv) a Middle Jurassic unconformity separates Lower to Middle Jurassic sedimentary and volcanic successions, which are related to subduction magmatism and the separation of the North and South American Plates, from Upper Jurassic continental and marine deposits in extensional basins along the northern margin, which record the opening of the proto–Caribbean sea. Future geochemical studies in Jurassic intrusive bodies should be able to evaluate the contamination of Triassic versus Grenvillian and older continental crust. Metamorphic studies should concentrate on the petrology and the pressure–temperature–time (P–T–t) paths. The chronostratigraphic framework of sedimentary basins should be improved by resuming paleontological investigations and geochronological analysis at the base and top of volcanoclastic rocks. Sedimentological analysis should focus on establishing the geometry of sedimentary basins, the relationship of basin generation with magmatic centers, and documenting the record of paleo–climate indicators in order to establish possible paleo–latitudinal variations of tectonic blocks. Paleomagnetic studies should be conducted at different localities in Lower – Middle Jurassic rocks to test whether tectonic blocks are static or record northward translations. The strong decrease in magmatic activity during the Late Jurassic time should be explained within a regional tectono–magmatic framework.

Keywords:   Jurassic, tectonic evolution, Gondwana, orthogonal margins, geodynamics.