ISSN:
1573-5117
Keywords:
paleolimnology
;
Pleistocene aridity
;
calcite
;
dolomite
;
gypsum
;
laminated gyttja
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The transition from an arid, glacial Late Pleistocene to an early Holocene (Gamblian ‘pluvial’) moist period has not been documented in Central America. Finding accessible volcanic lakes too youthful, and knowing that most Florida and Yucatan lakes were dry during glacial ages, we sought appropriate deposits lying deeper than 40 m in the deeper karst lakes of the Peten, in northern Guatemala. The bottom half of a 19.7 m core from Lake Quexil, and the bottom third of a 15 m core from Lake Salpeten, appear to be of Pleistocene age. The sediments contain lacustrine shells, sponge spicules, and Pinus pollen, and include several bands of humified gyttja with fragments of wood, but are dominantly montmorillonitic and mixed-layer clays and may be in part colluvial, like the later Holocene Maya clay. Calcite, gypsum, and (in presently saline Lake Salpeten only) dolomite indicate shallow, closed, moderately saline lakes 30–40 m lower than at present. In both cores a layer of inorganic sediment with gypsum dominant, perhaps recording the most arid phase of the glacial Late Pleistocene, overlies a similar clay layer with calcite dominant. As calcite and dolomite occur throughout the section(s), both minerals are believed to be detrital, but one source of calcite is algal crusts, formed and exposed today in the littoral and supralittoral zones. The early Holocene rise of lake levels formed several meters of fossiliferous gyttja with pollen of mesic tropical forest, now assigned to the pan-tropical Gamblian moist episode. Where deposited in oligomictic or meromictic lakes 〉 30 m deep, Gamblian gyttja of pollen zone Pl is finely laminated, the dark layers being richer in Ptot and Stot and poorer in Fe, Mn, Mg, and K than the light (clay) layers, but we cannot yet say that the laminae are annual.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00028454
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