Claim · model-written summary
Pollen records from Head Lake suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation.
- Outcome
- expansion of oaks and juniperse3
- Direction
- expansione3
- Qualifier
- at the Pleistocene/Holocene boundarye3
- Setting
- San Luis Valley, Coloradoe3
Quercus
JuniperusNot reportedMaterialGeneCompoundOrgan / stageInteractorInteractor roleSecond interactorSecond interactor roleTreatmentComparatorValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“In the San Luis Valley, Colorado, pollen records from Head Lake on the basin floor suggest an expansion of oaks and junipers at the Pleistocene/Holocene boundary that may indicate increased summer precipitation. Lake levels of Head Lake fell sharply after ca. 9500 yr BP.”
Title
The timing of late Quaternary monsoon precipitation maxima in the southwest United States.
David S. Shafer UA Campus Repository (The University of Arizona) 1989
Other claims from this paper (18)
- Association High percentages of Pinus and Juniperus pollen at Montezuma Well suggest a shift from winter to summer precipitation between ca. 12,000 and 9000 yr BP.
- Association Maximum influxes of Quercus and Gramineae pollen at Montezuma Well suggest a shift to summer precipitation between ca. 12,000 and 9000 yr BP.
- Observation Maximum aridity occurred between 7000 and 4000 yr BP, coincident with the lowest lake levels.
- Association High Artemisia to Chenopodiaceae-Amaranthus pollen ratios at Fryingpan Lake suggest precipitation maxima until ca. 6000 yr BP.
- Association High Artemisia to Chenopodiaceae-Amaranthus pollen ratios at Posy Lake suggest precipitation maxima until ca. 5000 yr BP.
- Observation Pinus edulis, P. ponderosa and Quercus gambelii were present on the western Colorado Plateau throughout the Holocene.
- Observation Ecotones of Pinus edulis, P. ponderosa and Q. gambelii moved upslope after ca. 6000 yr BP.
- Observation Expansion of shadscale steppe vegetation at low elevations suggests a period of maximum aridity from decreased summer precipitation.
- Observation Low lake levels between ca. 5000 and 3700 yr BP suggest a period of maximum aridity.
- Observation Lake levels of Head Lake fell sharply after ca. 9500 yr BP.
- Observation Pinus ponderosa was established in the Como Lake area by ca. 12,000 yr BP.
- Observation Pinus edulis was established in the Como Lake area by ca. 9500 yr BP.
- Observation Summer precipitation maxima may have lasted later into the Holocene on the High Plateaus, until ca. 6000-5000 yr BP.
- Observation Summer precipitation maxima may have lasted later into the Holocene in central Colorado, until ca. 4000 yr BP.
- Mechanism Regional orographic uplift may be responsible for the duration of summer precipitation maxima in the highland regions.
- Observation Sites in the southern Great Basin and Mohave Desert may have recorded enhanced summer precipitation earlier than highland sites.
- Observation The paleoecologic record generally confirms model predictions that southwest monsoon circulation was enhanced from 12,000 to 6000 yr BP.
- Mechanism Southwest monsoon circulation was enhanced from 12,000 to 6000 yr BP in response to insolation peaks.