Oxygen-isotope correlation of marine terraces and uplift of the Mesa hills, Santa Barbara, California, USA

Abstract

Resolving the chronology of marine terrace sequences is critical for determining uplift rates along tectonically active coastlines. Unfortunately, lack of suitable dating materials often makes this difficult. We present here oxygen isotopic data from 21 shells of Olivella biplicata from four marine terraces in the Santa Barbara and Ventura area located in southern California, USA. Terraces U-series dated at 47+0.5kaBP at Isla Vista and 70 4-2 ka Be at Santa Barbara City College (SBCC) provide age control for the isotopic data. Shells from the Isla Vista and SBCC terraces yield average values of 1.117%o and 0.627%o, respectively, and shells from a non-U-series dated terrace at Punta Gorda and an undated terrace at Santa Barbara Point yield average values of 1.010%o and 0.751%o, respectively. The data indicate that stable oxygen isotopic signatures preserved in marine terrace molluscs provide a useful tool for correlating undated terraces with those of known age. Furthermore, we are able to correlate samples collected from offset fragments of the Punta Gorda terrace on either side of the Red Mountain fault, demonstrating the utility of this method for correlating terraces across structural features. Using oxygen isotopic data coupled with the U-series dated wave-cut platform at SBCC we calculate a rate of uplift ranging from 0.62 + 0.03 mm/year (where the elevation of the first emergent terrace is 41 m) to 0.54 + 0.05 mm/year (where the elevation of the first emergent terrace is 36 m) for marine terrace flights preserved on the Mesa hills anticline located in the city of Santa Barbara, California.Coastal areas which have experienced uplift during the Late Pleistocene to present are typically characterized by a series of uplifted marine terraces resembling a flight of stairs. Each terrace forms at sea level as a wave-cut platform overlain by a thin veneer of marine sediments which are capped by more extensive terrigenous sediments, and, often, vegetation. The interface between the wave-cut platform and its sea-cliff is called the shoreline angle, and, as it usually lies within one or two vertical metres of the mean sea level (Lajoie et al.

Quaternary sea-level history of the United States

“…3), where the "big bend" in the San Andreas fault zone results in a compressional tectonic style. Later U-series dating of corals has confirmed the midWisconsin, ∼80,000 and ∼120,000 yr age estimates of many localities that were correlated by amino acid methods (Muhs et al, 1990(Muhs et al, , 2002bStein et al, 1991;Trecker et al, 1998). Radiocarbon dating has confirmed the Holocene terrace ages (Lajoie et al, 1979;Sarna-Wojcicki et al, 1987).…”

Shelf evolution along a transpressive transform margin, Santa Barbara Channel, California

“…45 ka) terrace emerges above present sea level west of Carpinteria and rises to an elevation of ~200 m a few kilometers to the east near Punta Gorda (Figs. 2, 20A; Lajoie et al, 1982;Trecker et al, 1998;Frederickson, 2016). Figure 23 shows a range of proposed sea-level curves for the Santa Barbara Channel region.…”

“…Folded and faulted strata along the fault and in its hanging wall are as young as Holocene. Estimated coastal uplift rates based on marine terraces range from ~0.15 mm/yr to as much as 5-8 mm/yr (Lajoie et al, 1982(Lajoie et al, , 1991Muhs et al, 1992;Rockwell et al, 1992Rockwell et al, , 2016Trecker et al, 1998;Duvall et al, 2004;Gurrola et al, 2014), the variability reflecting both location and conflicting interpretations. Uplift of the Santa Ynez Mountains has occurred within the past 5 m.y.…”

Coastal tectonics on the eastern margin of the Pacific Rim: late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

“…Subsequent work has confirmed this early estimate with a U-series age on coral of~4 9 ka (Gurrola et al, 2014; see also isotopic data in Table 2), correlative with some part of MIS 3. The terrace probably formed 62 m below present sea level and has been subsequently uplifted to elevations of about 14e35 m above present sea level (Trecker et al, 1998;Gurrola et al, 2014). Based on the age and elevation of this marine terrace, Gurrola et al (2014) estimate uplift rates of 1.6e2.0 m/ka.…”

“…Thus, south of this major restraining bend, faults of the western Transverse Ranges strike eastewest and fold axes also strike eastewest. Along the coast between Goleta/ Santa Barbara and Ventura, which is part of this major fault and fold belt, there are numerous geomorphic indicators of rapid crustal deformation, including uplifted, faulted, and folded marine terraces Lajoie et al, 1979;Wehmiller, 1982;Sarna-Wojcicki et al, 1987;Trecker et al, 1998;Minor et al, 2009;Gurrola et al, 2014).…”