The earliest Human settlers are
thought to have entered the Americas across the Bering Straits during the last
glaciation when sea levels were much lower than today, spreading across the
Americas during the Late Pleistocene and early Holocene. Several tool making
cultures are known from across the Americas during this time interval.
However the Pacific Northwest of North America, where these cultures are
thought likely to share a common root, is notoriously lacking in archaeological
sites from this era, and those that are known are mostly problematic to date.
In a paper published in the
journal PaleoAmerica in January 2015, Robert Kopperl, Amanda Taylor and Christian Miss
of SWCA Environmental Consultants, Kenneth Ames of the Anthropology Department
at Portland State University and Charles Hodges of Pacific Geoarchaeological Services describe the newly discovered Bear Creek archaeological site (site 45KI839)
at Redmond on the western Washington Puget Lowland in Washington State, which
has yielded a variety of stone tools from the Late Pleistocene-Holocene
transition.
Location of the Bear Creek site (45KI839) near the north shore of Lake
Sammamish, Puget Lowland, Washington. Kopperl et al. (2015).
The site was first identified in
2008 when scattered lithic artefacts were found above a layer of tephra and
peat. Excavations in 2009 and 2013
revealed a distinctive horizon, identified as Stratum Vc, which yielded a high
number of lithic artefacts, including bifaces, scrapers, gravers, projectile
points, and unifaces, as well as hammerstones and edge-modified flakes and
cobbles, made from chert and fine-grained volcanic rock.
Projectile point bases recovered in situ in Stratum Vc from 2009 test
excavation (#2009–50 and –181) and 2013 data recovery (#2013–1156). Kopperl et al. (2015).
Stratum Vc lies on top of a layer
of glacial sediments, Stratum VI, and is overlain by a layer of peaty wetland
deposits, Stratum Vb and then a layer of Diatomaceous Earth, Stratum II. This
is consistent with a warming climate at the end of the Pleistocene, with the
glacial deposits formed in a glacial setting, then replaced by wetlands and a
lake (Diatomaceous Earth is formed by freshwater Diatoms, a form of
single-celled Algae, settling out of the water column far enough from shore to
that other sediments are not being laid down). The entire assemblage is cut
through by an erosional sandy channel deposit, Stratum III, which also contains
some lithic artefacts, apparently reworked in nature.
Schematic profile of stratigraphy across the Bear Creek site (45KI839).
Primary in situ artifact-bearing LPH deposit is Stratum Vc, shown in red.
Kopperl et al. (2015).
The artefacts show a mixture of
traits associated with the Palaeoindian Period (roughly from 18 000 to 8000 BC) and Palaeoarchaic Period (roughly from 8000 to 6000 BC),
suggesting that they may date from close to the Pleistocene-Holocene boundary (about 10 000 BC). Importantly it was possible to obtain Radiocarbon Dates from several
pieces of carbonized and uncarbonized wood and peat samples within the
sequence, including a piece of carbonized wood from within Stratum Vc, dated to
12 770-12 596 years before the present, suggesting that the site may date from
the Younger Dryas Period (a short burst of cooling and return to glacial
conditions during the thaw at the end of the last glaciation), though a single
carbon date is not generally considered absolutely reliable. The clay layer at
the base of Stratum Vc has yielded two pieces of uncarbonized Willow wood,
which yielded dates of 12 597-12 116 and 12 690-12 420 years before the present
– this is actually slightly younger than the date from Stratum Vc, suggesting
that it may be inaccurate, but still within the Younger Dryas. Stratum Vb has
produced a range of dates, ranging from 10 586-10 298 to 8543-8376, i.e. the
very latest Pleistocene and Early Holocene.
See also…
The Taíno people are thought to have colonized the Caribbean Islands by island hopping from northern South America from about 500 BC onwards, reaching Jamaica by around 645-898 AD. They were skilled agriculturalists, introducing crops such as Cassava and Maize from South America and changing...
The earliest people arrived in the Americas some time between 12 000 and 13 500 years ago. They are known from burials and tools scattered (albeit thinly) across both North and South America. Art made by these...
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