Seismic expression of Pleistocene paleoceanographic changes in the California Borderland from digitally acquired 3.5 kHz subbottom profiles and Ocean Drilling Program Leg 167 drilling

Abstract

[1] We correlate processed 3.5 kHz seismic profiles with physical properties of cores collected during ODP Leg 167 from the Tanner, East Cortes, and San Nicolas Basins through much of the Pleistocene succession. Results indicate that seismic horizons in the unconsolidated Pleistocene sediments (top 50 m) are mainly controlled by density contrasts. Removing of the compaction trend from the density reveals a very interesting relationship between density and composition -the density closely and inversely correlates with organic carbon indicating that large-scale variations in organic carbon are responsible for seismic reflections through their influence on density. This is a significant discovery since there apparently is no other paleoceanographic setting that we know of where such a close linkage between acoustic properties and organic carbon has been established. The variations in organic carbon are mainly marine in origin and derive from variations in primary productivity associated with upwelling and the preservation regime related to oxygenation of water. Pleistocene reflections on 3.5 kHz profiles in the Borderland province thus record regional cyclical fluctuations in the paleoclimatic signals. The close resemblance in the density profiles at the three different basins indicates that the sedimentary regime was similar in those basins through the Pleistocene. These common density patterns produce regional seismic horizons that correlate well among the basins. It is likely these correlated and dated horizons could be extrapolated to other Borderland basins (e.g., San Clemente), where they can potentially be used as time markers for neotectonic studies in the region.

Morphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland (USA)

“…Age constraints from basin sampling provide regional context for seismic stratigraphy in the ICB basins (e.g., Emery, 1960;Moore, 1969;Gorsline et al, 1984;Gorsline and Douglas, 1987;Teng and Gorsline, 1989;Brothers et al, 2018). Stratigraphic control in the ICB basins comes from Ocean Drilling Program (ODP) sites in the Santa Monica Basin (ODP Leg 167, Site 1015; e.g., Normark and McGann, 2004;Normark et al, 2004b;Romans et al, 2009) and in the San Nicolas Basin (ODP Leg 167, Site 1013; e.g., Shipboard Scientific Party, 1997;Janik et al, 2004;De Hoogh, 2012). Stratigraphic age constraints also come from industry wells in some nearshore areas (e.g., Sorlien et al, 2015) and from shallow sediment cores and grab samples (Nardin et al, 1979;Barron, 1986;Vedder et al, 1986;Vedder, 1990;Normark et al, 2004b).…”

Morphology, structure and evolution of California Continental Borderland restraining bends

“…Oblique rifting of the Inner Borderland during the Neogene evolution of the PAC-NOAM transform fault boundary could have created this north-trending structural fabric that controls the younger faulting. Dunbar 1981;Legg 1985;Lyle et al 1997;Janik 2001) are used to estimate the maximum age of the deepest growth wedge, about 1.0-1.5 Ma. Sequence PEL is estimated to be about 460 + 240 ka (Smith & Normark 1976;Legg 1985).…”

A Comprehensive Assessment of Submarine Landslides and Mass Wasting Processes Offshore Southern California

“…The sedimentation rate (average of 65 m/Myr) remains relatively constant throughout the sequence without any sharp lithologic or age transitions (Shipboard Scientific Party, 1997). We map the slide debris‐capping surface at the base of the ∼15 m drape over to the Site 1013 drill hole using Chirp data (following Janik et al., 2004; Figure 3c), correlating the debris‐capping surface to the age model at ∼350 ka. The average sedimentation rate in the upper 35.66 m of Site 1013 is slightly higher than average at 77.5 m/Myr, which suggests the ∼15 m drape has accumulated since ∼200 ka.…”