Preliminary Report on the Archaeology and Paleoecology of the Abalone Rocks Estuary, Santa Rosa Island, California
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PRELIMINARY REPORT ON THE ARCHAEOLOGY AND PALEOECOLOGY OF THE ABALONE ROCKS ESTUARY, SANTA ROSA ISLAND, CALIFORNIA TORBEN C. RICK1, DOUGLAS J. KENNETT2 AND JON M. ERLANDSON2 1Department of Anthropology, Southern Methodist University, Dallas, TX 75275-0336; [email protected] 2Department of Anthropology, University of Oregon, Eugene, OR 97403-1218 Abstract—Although California’s mainland coast was once punctuated by numerous large embayments, estuaries are rare or absent on the Channel Islands. Recent archaeological and paleoecological research, however, confirm the presence of an estuary near Abalone Rocks, Santa Rosa Island. Preliminary survey and small-scale excavations suggest that early island peoples harvested shellfish (e.g., venus clams [Chione spp.], Washington clam [Saxidomas nuttalli], California oyster [Ostrea lurida]) from this estuary between about 8,000 and 5,900 calendar years BP. Rocky intertidal shellfish appear to dominate many of these assemblages, but the high proportion of estuarine shellfish is unique among Channel Islands archaeological sites. Our preliminary investigations suggest that the Abalone Rocks Estuary persisted for at least 2,000 years, with its transition to a freshwater/estuarine marsh possibly occurring around 5,000 years ago. This estuary, nearby Torrey pine grove, and other diverse coastal environments made the eastern portion of Santa Rosa Island an attractive place for ancient human settlement. Future work will investigate the nature of these sites, hypothesized to be either relatively permanent habitations or temporary encampments used by people living elsewhere on the islands. Keywords: archaeology, estuary, harvest, history, paleoestuary, shellfish INTRODUCTION Channel Island faunal assemblages are primarily dominated by the remains of rocky intertidal The Chumash and their predecessors lived on shellfish (California mussel [Mytilus califor- the northern Channel Islands for over 12,000 years, nianus], black abalone [Haliotis cracherodii] and leaving behind a lengthy and continuous red abalone [H. rufescens], turbans [Tegula spp.], archaeological record. The Channel Islands have etc.), rocky near shore or kelp bed fishes (rockfish hundreds of shell middens that contain the remains [Sebastes spp.], perch [Embiotocidae], California of a variety of fishes, marine and terrestrial sheephead [Semicossyphus pulcher], etc.), marine mammals, shellfish, birds, and other organisms. The mammals, and birds, with the frequency of various animal remains from these sites provide valuable resources often indicating environmental shifts or indicators of local and regional environmental human impact on local environments (Erlandson et changes and human impacts on marine and al. 2004). These data stand in sharp contrast to many terrestrial ecosystems (Glassow 1993, Kennett and early Holocene archaeological sites located on the Kennett 2000, Erlandson et al. 2004). Therefore adjacent mainland coast where a number of large these assemblages provide an excellent opportunity estuaries were a focus of early human settlement to investigate broad ecological and cultural issues and subsistence (Erlandson 1994). After sea level with great time depth and relatively high resolution. rise slowed around 6,000 to 5,000 years ago (Inman Archaeological research in sites spanning the 1983) most of these estuaries disappeared, with only last 10,000 years suggests that ancient Channel a few of the larger embayments persisting into the Islanders exploited a relatively similar suite of late Holocene (e.g., Goleta Slough). marine resources throughout the Holocene (Kennett In this paper, we summarize current 1998, Erlandson et al. 1999, Erlandson et al. 2004). archaeological evidence for the presence of a 56 RICK ET AL. paleoestuary, Abalone Rocks Marsh, near the The Abalone Rocks marsh/estuary system was mouth of Old Ranch Canyon on eastern Santa Rosa named by Cole and Liu (1994) because of its close Island. Several archaeological sites clustered proximity to Abalone Rocks. For this paper, we around the former estuary, now a marsh, contain refer to the Abalone Rocks Estuary as the estuary abundant estuarine shellfish species that are and marsh complex located at the mouths of both practically non-existent in other Channel Islands Old Ranch and adjacent Old Ranch House canyons. sites. We begin by providing a brief environmental The Abalone Rocks Marsh is frequently described and cultural overview of Santa Rosa Island and the as an estuarine marsh, but the limited open ocean Abalone Rocks estuary and marsh system. We then input suggests it is predominantly a freshwater describe the archaeological sites that contain system today. The marsh has been cored for estuarine shellfish species and speculate on the paleoecological research by Cole and Liu (1994) extent, productivity, and history of this ancient and Anderson (2002), producing records spanning estuary. Our data illustrate the importance of roughly 5,200 and 6,150 RYBP, respectively (ca. archaeology for reconstructing ancient environ- 7,000 calendar years). Both studies suggest that ments and the role of people in influencing and during the middle Holocene the system was tracking environmental changes. dominated by marine rather than freshwater conditions (Cole and Liu 1994, Anderson 2002). The late Holocene sequence is characterized by ENVIRONMENTAL AND CULTURAL greater freshwater input into the marsh and more CONTEXT vegetation on the surrounding uplands (Cole and Liu 1994, p. 332; Anderson 2002, p. 8). These With an area of roughly 217 km2, Santa Rosa records also contain evidence of local fire history Island is the second largest of the northern Channel and dramatic environmental changes (e.g., Islands. It is situated about 44 km off the mainland introduced vegetation and higher sedimentation) coast, about 5 km east of San Miguel Island and 9 following Euroamerican settlement of the island. km west of Santa Cruz Island. With a number of Recent research has shown that Santa Rosa relatively well-watered streams, mountain peaks Island was occupied by people for over 12,000 up to 508 m high, and several distinct vegetation calendar years (Johnson et al. 2000) and a number communities, Santa Rosa Island contains some of of shell middens have been dated to around 9,000 the greatest biological and environmental diversity years old (Erlandson 1994, Kennett 1998, on the Channel Islands. Introduced grasses Erlandson et al. 1999). Santa Rosa also has a currently dominate island vegetation, but there is continuous and well preserved archaeological also unique coastal beach and dune vegetation, record of Native American occupation spanning the island chaparral, oak and riparian woodland, and Holocene through the early 19th century. These an island endemic species of Torrey pine (Pinus factors make Santa Rosa Island an excellent torreyana insularis Schoenherr et al. 1999, p. 278). laboratory for studying the effects of humans on The eastern portion of Santa Rosa Island is aquatic ecosystems over broad periods of time among the most ecologically diverse areas of the (historical ecology; Crumley 1994), including an Channel Islands. Old Ranch Canyon, positioned on archaeological history of the Abalone Rocks the east coast between Skunk and East Points, is Estuary. the largest drainage on the island (11.83 km2) and has a broad plain at its mouth. Just beyond the upper reaches of Old Ranch Canyon is a relict ARCHAEOLOGY OF THE ABALONE Torrey pine grove and nearby Skunk Point is a ROCKS ESTUARY surf-swept sand spit with abundant habitat for seabirds and other animals. Located throughout Currently, seven archaeological sites located this area are numerous archaeological sites, on eastern Santa Rosa Island contain a high including the Chumash village of Qshiwqshiw proportion of estuarine shell. These sites are (Kennett 1998, Johnson 1999) and sites spanning located over a relatively large area with most on or at least the last 8,000 years. near the former shoreline of the estuary. However, ABALONE ROCKS ESTUARY 57 two of the sites (SRI-77 and SRI-667) are located our preliminary study of the Abalone Rocks near Beecher’s Bay about 3–4 km from the estuary. Estuary adds to this growing body of research. The chronology, location, and nature of the All of the shellfish remains analyzed in this shellfish assemblages from each of these sites study were identified using collections and provided evidence of the extent, productivity, and reference materials housed at the Department of history of the Abalone Rocks Estuary. Most of Anthropology, University of Oregon. We calculated these sites have yet to be excavated in detail, but Minimum Number of Individuals (MNI) using the radiocarbon dates are available from several of the highest number of non-repetitive elements present sites and bulk midden samples from two of the in the samples (e.g., sided hinges for bivalves and sites provided preliminary quantitative data on the apices for gastropods). In the following section, we importance of various shellfish taxa. briefly synthesize the setting, chronology, and We relied on the presence and abundance of a nature of the shellfish assemblages from each of variety of shellfish to determine the availability and these sites. productivity of local marine habitats (Table 1). Changes in shellfish species are a valuable CA-SRI-77 indicator of ancient environments (Shackleton and SRI-77 is a dense shell midden located on a van Andel 1986, Claassen 1998). A number of prominent terrace on the east side of Beecher’s