Deep-water Tectono-Stratigraphy at a Plate Boundary Constrained by Large N-Detrital Zircon and Micropaleontological Approaches: Peninsular Ranges Forearc, Baja California, Mexico

Abstract

The distribution of sedimentary systems on Earth’s surface is intimately linked to tectonics, therefore, at plate boundaries the stratigraphic archive can unlock the timing and style of tectonism and relative plate motions. Using large-n detrital zircon and micropaleontological analyses, tied to field mapping and data collection, we unravel the timing of strike-slip motion and its influence on the development of a Cretaceous submarine canyon on a long-lived oblique-convergent margin. Structural analysis demonstrates that the canyon bedrock, composed of fluvial rocks (La Bocana Roja Fm., of maximum depositional age (MDA): 93.6±1.1 Ma), underwent both syn- and post-depositional contractional and extensional deformation during the Cenomanian-Turonian in response to dextral strike-slip movement. Relative sea-level rise associated with basin subsidence and hinterland uplift was coincident with incision and fill of a submarine canyon system (Punta Baja Fm., MDA 87.1±1.5 Ma to 84.9±2.0 Ma), which exploited structural lineaments in the bedrock. The canyon was filled by sediment derived from an uplifted magmatic arc during the Coniacian to Santonian, most likely shed from erosional topography associated with plutonic intrusions to the NE. Structural data suggest that oblique dextral strike-slip motion on the Pacific margin controlled the development and location of submarine erosion, and had ended by the earliest Santonian, significantly earlier than previously estimated. Basinward tilting led to uplift, followed by transgression and wave ravinement of the canyon fill, which was then overlain by a shallow-marine to fluvial system. Thus, the canyon was cut, filled, buried, uplifted and rotated basinward, planed off through wave ravinement, and onlapped by shallow-marine to fluvial sediments within an 8 Myr period. Our findings, in part, reconcile contrasting basin evolution models for the Late Mesozoic Pacific margin.

Evolution and architecture of an exhumed ocean-facing coarse-grained submarine canyon fill, Baja California, Mexico

“…1) in a timespan of less than 8 Myr (derived from Detrital Zircon dating, Kane et al, 2022). This succession of depositional environments has been described previously (Kilmer, 1963;Schile, 1974;Boehlke & Abbott, 1986;Morris & Busby, 1996;Kane et al, 2022) and is further contextualised below.…”

“…The conduit documented in this study is preserved as the Punta Baja Formation submarine canyon-fill, which was steeply incised into the fluvial Bocana Roja Formation bedrock, filled, planed off and onlapped by the shallow-marine El Gallo Formation (Fig. 1) in a timespan of less than 8 Myr (derived from Detrital Zircon dating, Kane et al, 2022). This succession of depositional environments has been described previously (Kilmer, 1963;Schile, 1974;Boehlke & Abbott, 1986;Morris & Busby, 1996;Kane et al, 2022) and is further contextualised below.…”

“…1,2). Rapid tectonically-forced base-level changes, faulting and basinward tilting controlled the juxtaposition of continental and marine sedimentary systems (Busby et al, 1998;Kane et al, 2022).…”

“…The Bocana Roja Formation is the oldest sedimentary unit in the study area (93.6±1.1 Ma Maximum Depositional Age (MDA) derived from Large-N Detrital Zircon dating (Fig. 3, Kane et al (2022)). The contact with the underlying Alisitos arc is not exposed (Kilmer, 1963;Schile, 1974).…”

“…Less studied exposures of the Late Cretaceous Punta Baja Formation provide continuous depositional strike and dip sections of the 120 m thick and 1.2 km wide feature, with 4.5 km of continuous dip exposure. Canyon inception and evolution has been linked to tectonics causing severe baselevel changes, constraining the canyon's lifespan to a maximum of 8 Myr (Kane et al, 2022). Multi-scale depositional architecture and depositional environments are interpreted using mapping, sedimentary logging, high-resolution photogrammetry, and detailed facies descriptions.…”