The Late Aptian to Early Albian transition has previously been
identified as a possible example of substantial climate cooling within
the mid-Cretaceous greenhouse period. To study the response of
continental weathering and terrestrial vegetation to this cooling
episode at low- to mid-latitudes, marine nearshore deposits from the
Algarve Basin (SW Portugal) have been investigated with a combined
approach including palynology, clay mineralogy and bulk-rock
geochemistry. In the Lower Aptian part of the succession, quartz-rich
sandstone facies is accompanied by high abundances of early diagenetic
kaolinite, which is interpreted to reflect episodes of enhanced humidity
and high meteoric flow-through. In contrast, the Late Aptian to Early
Albian deposits are characterized by high abundances of detrital clay
minerals (mica and chlorite) indicating the dominance of physical
weathering processes in the source area, most probably related to low
precipitation rates in conjunction with tectonically enhanced erosion.
Palynological data show a strong dominance of Classopollis pollen
associated with low pteridophyte spore abundances, suggesting warm
semi-arid to arid palaeoenvironments. Changes in sedimentation patterns
from varicoloured lagoonal marls to thick-bedded shallow-water
carbonates are neither expressed in the spore-pollen assemblages nor in
the distributions of clay minerals which both remain essentially stable
throughout the Late Aptian to Early Albian. These relatively stable
patterns are in contrast with various lines of evidence, predominantly
from high-latitude areas, that suggest a significant cooling during this
time interval. Our study demonstrates that terrestrial environments of
low- to mid-latitude regions were not significantly affected by the Late
Aptian - Early Albian ``cold snap''.