PLUVIAL LAKES

Like “Glaciations“ , a classical indicator of Pleistocene climate change.
Pluvials“ (high lake levels) were assumed to be roughly contemporaneous with “glacials.“

Founders of U.S.A. Great Basin Pluvial history
  • I.C. Russell 1883-89 Lake Russell (Mono Lake)
  • G.K. Gilbert 1890 Lake Bonneville (Great Salt Lake)

Climatic Factors: both precipitation and temperature important.
The word "pluvial" implies precipitation, but lower temperature can reduce evaporation and produce lake level increases; e.g.,
    Temperature 5 oC lower = 1/4 less evaporation

WATER BUDGET (for a lake without an outlet):
    ALPL + ATPTk + GI = ALE + GO

    AL = lake area PL = precipitation on lake
    AT = catchment area PT = precipitation in catchment area
    GI = groundwater inflow GO = groundwater outflow
    k = runoff coefficient (soils, steepness)
    E = evaporation


Other Important Factors

  1. Seasonality and intensity of precipitation
    • runoff (intense flooding, snow vs. rain)
    • evaporation (winter vs. summer, water & air temperature)
  2. Vegetation and Soil Cover
    • runoff, transpiration, interception
  3. Basin Geology
    • Basin Shape (evaporation) Surface area / volume
    • Tectonic/Volcanic Dams Stream Diversion
        Walker Lake / Carson Sink - Walker River meandering
        Pyramid Lake / Carson Sink - Truckee River diversion (Adams et al., 1999)
        Lake Cahuilla - Colorado River diversion (Waters, 1980)
        Pharanagat Marsh - Faulting, uplift of outlet
        Lake Bonneville - Bear River Diversion (volcanic)
WUS	Pluvial Lakes

WESTERN NORTH AMERICA PLUVIAL LAKES




Lake Estancia
Lake Bonneville: 500 km N-S, 355 m max depth
  • Bonnneville stage area: 51,690 km2
    vol.: 7500 km3, over-flow 1565 m > 1470 m (14,500 yr B.P.)
  • Guilbert area: 17,000 km2
  • Neoglacial (2-3 Ka) area: 10,000 km2
  • Modern area: 4,700 km2


Lahontan: 280 m max depth, area 22,900 km2, highest 1330 m
  • several inter-connected basins, effected by stream diversion
  • Walker Lake studied by long deep core


Owens River Series: chain of lakes
  • Mono Lake (L Russel) (1980 m)
    Early Neoglacial (3770 ya) high stand (Stine, 1990)
  • Owens L. (1081 m)
  • China L. (657 m)
  • Searles L. (690 m)
  • L Manly (87 m)


Lake Cochise (Willcox, AZ): 29 m max depth
high 13,750 - 13,400 yr B.P., 8900, 5400, 3-4000 yr B.P. (Waters, 1989)


PLUVIAL CLIMATE Last Cycle:

History of Lake Level varies with climatic regime.
Monsoon vs. Mediterranean.

Mediterranean Climate
Northern Great Basin: lakes full 14-15 ka, low by 11,500 yr B.P.
moderate raise in the early Holocene and the early Neoglacial
Smith and Street-Perrott, 1983

Monsoonal Climate
Southwestern G.B. lakes re-fill 12 K - 10 ka (Oviatt, 1988)
Other monsoonal regions (Saharan Africa - Northern India): dry during full-glacial (stage 2), full during early-Holocene monsoonal maximum
Harrison, 1993

PLUVIAL CLIMATE Previous Cycles:

  • Bonneville and Lahontan deep-lake cycles start ca. 800 ka
  • Last phase = "Alpine" for Great Salt Lake Basin, 6 earlier cycles
  • Most important Bonneville site "Little Valley" Promintory Range
  • Geological evidence from
      beach strand lines, dated by volcanic ashes
      alternating lake-sediment & soils, dated by volcanic ashes
      lake sediment cores, dated by volcanic ashes
  • Lake Bonneville Pluvial Chronology
      MIS   PLUVIAL   GLACIAL
    Stage 2   Bonneville   Pinedale
    Stage 6   Little Valley   Bull Lake
    Stage 8   Pokes Point   Pre- Bull Lake
    (Davis, 1998)


PROGLACIAL LAKES

  • Continental Glaciers blocked river drainage, produced very large proglacial lakes
  • Resulted in river diversions that determined aquatic animal and plant distribution changes (Lougee, 1953; Pielou, 1991)


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