Late Paleozoic
Ice Volume Controls on the Paleoclimate and Stratigraphic Record of
Cecil, C. Blaine1, Frank T.
Dulong1, Isabel Montanez2 (1)
The late Paleozoic stratigraphic
record from southern Euramerica documents paleoclimate changes that were coincident with, and linked
to, global climate modes. Carbonates, orthoquartzites,
and chert developed during a warm-mode in the early
Devonian. Weak latitudinal climate gradients and feeble wind-driven circulation
during the Middle Devonian warm mode resulted in organic-rich fine-grained
sediments. Waning of the Devonian warm-mode (Famennian) lead to sea level fall, seasonal rainfall,
continental red beds, and calcic-paleosols. Glaciogenic deposits, chemically
reduced continental siliciclastics, abundant
terrestrial organic matter, and intensely leached paleosols
are coincident with a cool mode that persisted from the late Famennian into the mid-Visean
(late Osagean). An abrupt change in sedimentation in
the mid-Visean (late Osagean?)
to carbonates, evaporites, and eolianites
documents a shift to aridity associated with mid-Visean
global warming and sea level rise. The onset of the mid-Carboniferous cool-mode
is recorded in Serpukovian (late Chesterian)
strata by sea level fall and a progressive stratigraphic
increase in continental sediments and terrestrial organic matter. The
Mid-Carboniferous cool-mode is linked to a humid paleoclimate
that resulted in chemically reduced siliciclastics
and coal during the Bashkirian and Moscovian. Kasimovian red beds, paleo-calcic-Vertisols, and sea level rise document a
return to warm-mode dry conditions. Humid to dry-subhumid
conditions recorded in Gzhelian cyclothems
resulted in coal beds, chemically reduced siliciclastics,
and nonmarine limestones
respectively signaling the onset of Permian glaciation.
Both intermediate-term and long-term changes in the Late Paleozoic stratigraphic record in the low latitudes of southern Euramerica are best explained by both sea level change and
shifting atmospheric pressure belts in response to changes in ice-volume in the
southern hemisphere.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California