Table 1.
Summary of changing environmental conditions at Pinnacle Point at the scale of MIS.
Fig 1.
Simplified model of raw material availabilities based on current outcrop locations and mean modelled coastline distance for each MIS [43, 44].
The dispersed distribution of quartz is represented by the light green shade in the background. Each grid square is 5 km x 5 km. The uppermost row of stacked bar graphs present the relative frequencies of each raw material type within each MIS. The lower rows of stacked bar graphs present the relative frequency of cobble and outcrop cortex for each raw material type. Only quartzite and silcrete showed a significant association between cortex type and MIS (Table E in S1 Dataset).
Table 2.
Summary of minimum distances to different raw material types in each MIS.
Secondary sources (cobbles) depend on modeled sea levels [43, 44]. The distance for primary sources (outcrops) is presented under the assumption that lowered sea levels did not expose good quality outcrops.
Table 3.
Summary of analyzed sample from PP5-6.
Fig 2.
Correspondence plot of raw material types by MIS.
c1 explains 96% of variation. c2 explains 4% of variation. Pearson Chi2 = 2815, p<0.001.
Fig 3.
Vertical distribution of quartz frequency at PP5-6.
When lumped by MIS stage, relative quartz frequency is highest in MIS 4, though there is variability through the sequence. A. West view of PP5-6 lithic artifact plotted find X,Y,Z coordinates. MIS boundaries indicated by blue bounded areas are defined based on the mean OSL age estimate within StratAggs. Red points are quartz lithic artifacts, white points are lithic artifacts in other raw material types. Bar plots indicate frequency counts of raw material types and MIS. B. Relative point density map of north view of PP5-6 quartz lithic artifact plotted finds generated in ArcMap using the rectangular neighborhood option and based on point elevation. Classes defined based on 1/3 standard deviation. Because some of the deposits dating to late MIS 4 and early MIS 3 overlap with respect to elevation (Z), the MIS 3 relative density map was generated separately from the rest of the sequence and is depicted above the MIS 4 deposits in the point density column.
Fig 4.
Correspondence plot of raw material types by temporal trend.
c1 explains 78% of variation. c2 explains 27% of variation. Pearson Chi2 = 51.5, p = <0.0001.
Fig 5.
Summary of lithic technological responses to MIS 4 at PP5-6.
Each arrow is scaled to the number of proxy traits indicative of that technological response (Table O in S1 Dataset) and the direction of the arrow indicates the direction of the change relative to the y-axis. (a) Proxy traits for raw material source associated with glacial cycling are the presence of cortex chatter marks and interpreted cortex type based on roundness and marks. (b) Proxy traits for reduction stage and/or intensity associated with glacial cycling are cortex area and location, platform cortex, pre-heat treatment area and location, retouched piece typology, visible luster, cortical surface area estimate, dorsal scar count, length of final removal on core face 1, mass, maximum length, maximum thickness, mid-point thickness, pre-heat treatment surface area estimate, and technological length, lithic artifact class (frequency retouched pieces), and blank to core ratio. (c) Proxy traits for flaking efficiency associated with glacial cycling are aris orientation, Conard et al. unified core type, dorsal direction, aris orientation on core face 1, lithic artifact class (frequency blades), edge length to mass ratio, and blank to core ratio. (d) Proxies for tool function or use are presence of edge damage, retouch edge angle, retouched piece blank, retouched piece typology, retouch type, unretouched points, and retouch edge angle. (e) Proxies for percussion technique associated with glacial cycling are fissuring on platform, marks on the ventral surface, platform abrasion, platform delineation, platform morphology, and platform width to thickness ratio.
Table 4.
List of traits by raw material type that associate with MIS and exhibit a pattern consistent with glacial cycling for each raw material type.
Traits that do not show a significant association for any raw material type are excluded from this table. Definitions are provided in S1 File.
Table 5.
Summary of results.