Archaeological Investigations at Montaña de Oro State Park,

San Luis Obispo County, California

Flaked, Ground, & Battered Stone

Shale and Monterey chert are the most common toolstone types found in the immediate vicinity of CA-SLO-9. The surrounding coastal terrace includes abundant angular cobbles of Monterey chert and shale, the two often grade into one another so that the distinction between chert and shale is at times somewhat arbitrary. Shale ranges from coarse-grained chalky material to finer-grained siliceous material with flaking qualities comparable to chert. Chert found on and around the site ranges from tabular slabs of decent quality to blocky cobbles with heterogeneous structure and poor flaking qualities.

Two Projectile Points recovered from CA-SLO-9.

Raw Materials Used

Flaked Stone

The flaked stone collection includes 6,189 specimens including 19 cores, 11 core tools, 10 unifaces, 4 flake tools, 32 bifaces, 34 projectile points, 1 drill, 2 reamers, 15 notched stones, and 6,061 pieces of debitage. The following is a detailed description of each of these classes.

Cores—A total of 19 specimens were classified as cores including 16 of shale and 3 of Monterey chert. The cores generally reflected working of locally occurring cobbles, as 16 of the specimens were flat, fist-sized cobbles typical of those found in the immediate vicinity of the site. Two specimens were interior chunks and one was a tabular chunk. Seven of the cobbles appeared to have been opened using the bipolar technique.

Core Tools—Eleven artifacts were classified as core/cobble tools. Nine were shale and two were of Monterey chert. Ten of these were cobbles and one was an interior chunk. All specimens showed evidence of patterned flake removal and/or edge battering.

 

Core Tools recovered from CA-SLO-9.

Representative Unifaces from CA-SLO-9

Unifaces—Ten unifaces were recovered, most of which seem to represent a unique local industry that took advantage of the cleavage planes in local shale cobbles. Two of the implements were large broken interior flakes that may represent unfinished bifaces. The remaining eight were all manufactured from cobbles; seven of shale and one of Monterey chert.

Bifaces—Among the 32 bifaces recovered during the investigations, 18 were made from locally occurring shale and 14 were Monterey chert. All five stages were represented although the shale bifaces were limited to the early reduction stages. Fourteen of the shale specimens were bifacially modified cobbles. Cobbles of this type occur is the creek bed adjacent to the site and in the natural alluvial soils beneath the midden.

Shale Bifaces from CA-SLO-9.

Projectile Points—The 34 projectile points represented the most abundant formal artifact within the flaked stone class. Four types were represented: contracting-stemmed (N = 11), small leaf-shaped (N = 7), double side-notched (N = 1), and large side-notched (N = 1) (Table AI-8). Fourteen were indeterminate with respect to type. A total of 29 was Monterey chert, 4 were Franciscan chert, and 1 was shale.

Contracting-stemmed. Contracting-stemmed points were the most abundant type recovered, with 11 examples. One specimen was unique in that it was made from shale; all other specimens were manufactured from Monterey chert. Seven were complete or nearly complete, two were basal fragments and one was a tip fragment.

Contracting-stemmed projectile points from CA-SLO-9.

Small Leaf-shaped. With seven specimens, this was the second most abundant type Specimens similar to the examples in the current collection were recovered from a Late Middle – Middle-Late Transition context at SLO-179, and the type seems to be a good marker of this range of time. These are commonly interpreted as early arrow points, but they could also have served as tips for harpoons.

Small Leaf-shaped projectile points from CA-SLO-9.

Double Side-notched. This type is most common in the Cambria area where a number of examples were recovered from a mass burial at SLO-175. The northern examples were all made from a white chert, were very diminutive, and were clearly arrow points. The current specimen is a more robust artifact of Monterey chert. Double side-notched points were proposed as Middle-Late Transition markers at SLO-175.

Large side-notched. The single large side-notched example is a basal fragment of green Franciscan chert. Large side-notched points are generally good makers of the early Holocene, based on examples from San Luis Obispo County. Several were recovered from a Middle-Late Transition context at MNT-1233, however.

Double side- and large side-notched points from CA-SLO-9.

Drills and Reamers—Two reamers and one nearly complete drill were recovered. The reamers are typical of the Hunting Culture and resemble specimens from SLO-267 and MNT-521. The drill is a bifacial specimen that was apparently hafted.

Drill and reamer from CA-SLO-9

Notched Stones— Represented by 15 examples, notched stones were one of the most abundant formal artifacts represented in the sample. All of the artifacts were made from shale cobbles. Twelve were bifacial and three were unifacial. Two specimens are distinguished by the presence of asphaltum staining. Specimens were most frequently expediently manufactured, minimally modified cobbles but more deliberate, highly formalized versions were also recovered.

Notched stones with asphaltum staining from CA-SLO-9.

Debitage—A total of 6,061 pieces of debitage was recovered including 4169 of Monterey and Franciscan chert, 1865 of shale, 26 of obsidian, and one specimen of Grimes Canyon fused shale. The majority of the Monterey chert debitage falls within the three smallest size grades with only 8.7% of the flakes larger than 3 cm. Shale debitage from CA-SLO-9 is generally somewhat larger than chert debitage with 17.2% of the flakes larger than 3 cm and only 12.6% smaller than 1 cm.

Ground & Battered Stone

Pitted Stone—The pitted stone was recovered from the 80-90 cm level of Unit 8. It is a complete granite cobble with a single shallow pit on each opposing face. The specimen is 8.7 mm in length, 59.9 mm wide, and weighs 264 g. The pit on one face is 19.9 mm in diameter and 2.9 mm deep. The pit on the other face is 24.4 mm wide and 3.8 mm deep.

Battered Cobbles—A total of 12 battered cobbles were recovered including 10 of shale, one chert, and one of sandstone. The shale cobbles all appear to be derived from the local area. Some of the cobbles may represent hammerstones that were used in reduction of other cobbles and cores. Others may represent limited assaying of cobbles that were intended for further reduction.

Pitted Stone from CA-SLO-9

Battered Cobbles from CA-SLO-9