Characteristics of the Late Pleistocene forests on Santa Cruz Island, Californi

Santa Cruz Island (SCI) is one of the northern Channel Islands of California that were connected during the lowered sea levels of the Late Pleistocene. While today the island is dominated by coastal sage scrub and grassland, sediments from Canada de los Sauces (CdlS) on Santa Cruz Island (SCI), California have preserved a late Pleistocene plant macrofossil record that indicates that towards the end of the Last Glacial Maximum (LGM) a coastal conifer forest grew on the island. Dominant species found in the plant macrofossil record include Douglas fir (Pseudotsuga menziesii), Gowen cypress (Cupressus goveniana), and Bishop/Santa Cruz Island pine (Pinus muricata/remorata). Last analyzed in the 1930s, this study revisited the CdlS outcrops to (1) confirm and expand plant species found in the macrofossil record; (2) radiocarbon date material to better constrain the chronology of the fossil deposit; (3) understand the geologic context of deposition of the CdlS sediments; (4) compare the late Pleistocene flora with the modern vegetation of SCI; and (5) compare the Pleistocene CdlS record to other paleoecological records throughout the southern California region.;Eight new radiocarbon dates confirmed that the CdlS deposits span the period 17,589 to 15,852 cal yr BP, with an average median age of ~16,500 cal yr BP. Macrofossils identified from this study included: Pseudotsuga, Pinus muricata v. remorata, Pinus radiata (Monterey pine), Cupressus, three species of bryophytes, insects from several different groups, as well as termite fecal pellets (TFP) and carbonaceous spheres (CS). The occurrence of these fossils is consistent with an interpretation of a cool, moist, coastal conifer forest, with closed-cone pines, Douglas fir and coastal cypress. This vegetation type is now extinct on SCI. Cool temperatures associated with the Heinrich Event 1 (H1) (~15,000--18,000 cal yr B.P.) may have contributed to existence of this forest with increased precipitation and fog production.;Previous studies by Chaney and Mason (1934) had not recovered Pinus radiata, bryophyte species, or insect remains in their samples. A similar plant assemblage currently occurs ~530 km north of SCI in areas including Fort Bragg, Monterey, and Point Reyes, California. Findings of TFP and CS in deposits ~16,500 cal yr B.P. cast further doubt upon the Younger Dryas Impact Theory (~12,900 years ago). Geologic analysis of CdlS suggests that during the late Pleistocene fluvial sediment was deposited in a stream channel from possible flood events that carried the macrofossils with it too. Overall, the macrofossil deposit at CdlS offers a picture of late Pleistocene SCI with a coastal forest that differs much from the shrubland and grassland environment found during the current interglacial. Climatic change from the LGM to current Holocene interglacial largely attributes to this shift in vegetation regimes. Though this data does not tell us when this forest became extinct, in conjunction with other previously published data, we know that it did not survive into the Holocene.