Abstract Amino-acid and oxygen isotope data for fossils from terraces of the Palos Verdes Hills and San Pedro areas in Los Angeles County, California, shed new light on the ages of terraces, sea-level history, marine paleotemperatures, and late Quaternary tectonics in this region. Low terraces on the Palos Verdes peninsula correlate with the ∼80-ka and ∼125-ka sea-level highstands that are also recorded as terraces on other coasts. In San Pedro, the Palos Verdes sand (the deposit on what is mapped as the first terrace by Woodring and others, 1946) was previously thought to be a single deposit; amino-acid, oxygen isotope, U-series, and fauna] data indicate that deposits of two ages, representing the 80-ka and 125-ka highstands occur within this unit. Oxygen isotope data show that on open, exposed parts of the Palos Verdes peninsula, ocean waters during the 125-ka highstand were cooler than present (by about 2.3-2.6°C) similar to what has been reported for other exposed coastal areas in California. In contrast, in the protected embayment environment around San Pedro, water temperatures during the 125-ka highstand were as warm or warmer than present. During the 80-ka highstand, water temperatures were significantly cooler than present even in the relatively protected embayment environment of the San Pedro area. Late Quaternary tectonic-uplift rates can be calculated from terrace ages and elevations. Correlation of the lowest terraces around the Point Fermin area shows that the Cabrillo fault has a late Quaternary vertical-movement rate of 0.20 m/ka, based on the difference in uplift rates on the upthrown and downthrown sides of the fault. Elsewhere in the Palos Verdes Hills-San Pedro area, late Quaternary uplift rates vary from 0.32 m/ka to possibly as high as 0.72 m/ka. These rates, which reflect vertical movement on the Palos Verdes fault, are in broad agreement with estimated Holocene vertical rates of movement determined for offshore portions of the fault.

ABSTRACT The Ascension-Monterey Canyon system, one of the largest submarine canyon systems in the world, is located offshore central California. The system is composed of two parts which contain a total of six canyons: 1) the Ascension part to the north, which includes Ascension, Año Nuevo and Cabrillo Canyons, and 2) the Monterey part to the south, which includes Monterey Canyon and its distributaries, Soquel and Carmel Canyons. These six canyons have a combined total of 16 heads: one head each for Ascension, Soquel and Monterey Canyons, two heads for Año Nuevo Canyon, three heads for Carmel Canyon, and eight heads for Cabrillo Canyon. Ascension, Año Nuevo and Cabrillo Canyons coalesce in 2,300 m of water to form the Ascension Fan-Valley. Soquel and Carmel Canyons join Monterey Canyon at depths of 915 m and 1,900 m, respectively, to form Monterey Fan-Valley (the main channel of the system). Ascension Fan-Valley joins Monterey Fan-Valley on the proximal part of Monterey Fan in 3,290 m of water. The Ascension-Monterey Canyon system has a long and varied history. The ancestral Monterey Canyon originated in early Miocene time, cutting east-west into the crystalline basement of the Salinian block (possibly subaerially), somewhere near the present location of the Transverse Range of California. Since that time (~ 21 Ma), the Salinian block, riding on the Pacific Plate, moved northward along the San Andreas fault zone. During this period of transport the Monterey Bay region was subjected to several episodes of submergence (sedimentation) and emergence (erosion) that alternately caused sedimentary infilling and exhumation of Monterey Canyon. The present configuration of the Ascension-Monterey Canyon System is the result of tectonic displacement of a long-lived submarine canyon (Monterey Canyon), with associated canyons representing the faulted offsets of past Monterey Canyon channels. Slivering of the Salinian block along several fault zones trending parallel or sub-parallel to the San Andreas fault zone (the Ascension fault and the Palo Colorado-San Gregorio fault zone, in particular) displaced to the north the westerly parts of Monterey Canyon. In this manner Monterey Canyon “fathered” Cabrillo Canyon, Año Nuevo Canyon, Ascension Canyon and Pioneer Canyon, along with an unnamed canyon located between Ascension and Pioneer Canyons. Tectonics continue to dictate the morphology and processes active in the system today. The Palo Colorado-San Gregorio fault zone marks the continental shelf boundary in the Monterey Bay region and divides the canyon system into two parts, the Ascension and Monterey parts. The Monterey Canyon part has a youthful, V-shaped profile while the Ascension part, except for the heads that notch the shelf, and both fan-valleys exhibit more mature, U-shaped profiles. Earthquakes stimulate mass-wasting on the continental slope; most of the Ascension part of the system now receives its sediment from this source. The Monterey part, however, intercepts sediments carried by longshore transport and is the main regional conduit for terrestrial sediment transport to the abyssal plain.

Abstract This article uses measurements from outcrops of the Point Loma Formation to define the hierarchical organization of a distributive submarine fan and spatial changes in its constituent parts. A four-tier hierarchy for lobes is documented: bed, element, complex, and system. Across each hierarchical tier, there is an increase in size, duration of deposition, number of cross-cutting relationships, number of superposed stratal units, and degree of compensational stacking. Lobe elements contain systematic axis-to-margin and longitudinal decreases in amalgamation ratio, erosion, net sand content, proportions of sand-rich facies, and maximum grain size, with the exception of shale clasts in fringe position. The cross-sectional aspect ratios of lobe elements in the Point Loma are ~1000, a similar value to those measured in other systems, although aspect ratios are slightly higher at the distal reaches of lobe elements than in proximal locations. The key longitudinal patterns in lobe complexes are decreases in proportion of sand-rich facies, maximum grain size, amalgamation ratio of elements, net sand content, and amount of interelement erosion and a longitudinal increase in the degree of the amount of compensational stacking. Lobe complexes stack laterally and progradationally to build a lobe system.