Thermic systems of Guadeloupe caves : consequences on sedimentation and wall preservation

Cette communication a donné lieu à un poster disponible sur demande auprès de l'auteur. This has been presented on a poster available through a request to the author.Hygrometric and thermic measurements have been recorded to assess the microclimatology of some Guadeloupean caves. The results from Blanchard Cave and Morne Rita Cave, two Pre-columbian archeological sites, are presented here. Recordings have been conducted according to two modes: a short-step one which defines the daily cycle, and a long-term one which documents the annual cycle. Measurements show two distinct patterns: 1. The first cave records temperatures globally warmer than the exterior conditions. But the regime is very unstable due to air currents bringing cold air deep into the cave. The result is a limited hygrometry and a very high sensitivity to daily hygro-thermic variations. Annual data collection reveals fluctuations in the hot air trap system, that we link to the influence of seasonal cloud covering. 2. The second cave can be considered as a cold air trap. Lack of air currents helps to establish a more stable system, and a more humid air to be maintained in the cavity. Daily fluctuations are strongly weakened. However, seasonnal variations are still recorded. These data open up prospects for further understanding of physical processes occurring in these sites. Thus, air flows that have been highlighted in the first site can explain the presence of evaporitic minerals in the ancient deposits by seaspray transported into the cave with cold air flows. Highlighting this supply also support the assumption that salt fretting contributes heavily to wall desegregation. A 0.6 cm/century weathering rate is thus estimated from sedimentation age model. Such a rate would explain the total lack of engravings in this kind of cave. Conversely, the stable system in Morne Rita cave would have favored the preservation of the Pre-columbian art