The North American Cordillera during the Mesozoic to Paleogene: Selected questions and controversies

Abstract

ABSTRACT The North American Cordillera experienced significant and varied tectonism during the Triassic to Paleogene time interval. Herein, we highlight selected questions and controversies that remain at this time. First, we describe two tectonic processes that have hindered interpretations of the evolution of the orogen: (1) strike-slip systems with poorly resolved displacement; and (2) the closing of ocean basins of uncertain size, origin, and mechanism of closure. Next, we divide the orogen into southern, central, and northern segments to discuss selected controversies relevant to each area. Controversies/questions from the southern segment include: What is the origin of cryptic transform faults (Mojave-Sonora megashear vs. California Coahuila transform fault)? Is the Nazas an arc or a continental rift province? What is the Arperos basin (Guerrero terrane), and did its closure produce the Mexican fold-and-thrust belt? How may inherited basement control patterns of deformation during subduction? Controversies/questions from the central segment include: Can steeply dipping mantle anomalies be reconciled with geology? What caused high-flux events in the Sierra Nevada batholith? What is the origin of the North American Cordilleran anatectic belt? How does the Idaho segment of the orogen connect to the north and south? Controversies/questions from the northern segment include: How do we solve the Baja–British Columbia problem? How big and what kind of basin was the Early Cretaceous lost ocean basin? What connections can be found between Arctic geology and Cordilleran geology in Alaska? How do the Cretaceous tectonic events in the Arctic and northern Alaska connect with the Cordilleran Cretaceous events? What caused the Eocene tectonic transitions seen throughout the northern Cordillera? By addressing these questions along the length of the Cordillera, we hope to highlight common problems and facilitate productive discussion on the development of these features.