- Startpagina tijdschrift
- volume 9 (2006)
- number 3-4 - Han-sur-Lesse Symposium - nov. 2004
- COMPARATIVE ANALYSIS OF STALAGMITES FROM TWO CAVES OF NORTHERN SPAIN. IMPLICATIONS FOR HOLOCENE PALEOCLIMATE STUDIES
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COMPARATIVE ANALYSIS OF STALAGMITES FROM TWO CAVES OF NORTHERN SPAIN. IMPLICATIONS FOR HOLOCENE PALEOCLIMATE STUDIES
Abstract
Two caves from Northern Spain (Cueva del Cobre and Kaite) and their Holocene speleothems are comparatively analyzed in order to discuss their potential for paleoclimate studies. Both caves are almost at the same latitude (43º 01’ N), located in the southern slope of the Cantabrian ranges, and separated by only ~60 km. Despite the proximity, their karstologic, hydrogeochemical and climatic characteristics determine a markedly different speleothem development. Kaite is a small cave developed in Upper Cretaceous limestones and is located only 12-20 m below the surface, which today shows a poor vegetal soil cover. It is a relatively warm cave (10.4 ± 0.1 ºC) with permanent but variable water drip, richly decorated with speleothems. In contrast, Cueva del Cobre is a larger cave, developed in Carboniferous limestones, at depths of more than 100 m below surface. It is also colder (5.6 ± 0.1 ºC), with net influence of high mountain climate, and has scarcer speleothem development. The stalagmites of Kaite are cylindrical, thin and elongated, whereas those from Cobre are more conical, shorter and thicker. All the studied samples consist of calcite, and their oxygen and carbon isotope signals are valid for paleoclimate studies. A wide range of crystal fabrics is present in Kaite samples, reflecting changes in the forming conditions, whereas in Cobre columnar calcite is the dominant one. Annual laminations are easily recognizable in Kaite samples, but absent or diffuse in Cobre. Finally, hiatuses are more abundant in Kaite samples, reflecting a rapid response of the cave to abrupt changes in climate, and scarcer in Cobre, where the system, more isolated from surface, seems to have a larger environmental inertia. Kaite speleothems are thus more sensitive to rapid variations in climate, and an annual resolution can be reached in best cases. Cobre stalagmites in general show more continuous records and are quite sensitive to long-term (decadal to centennial) climate trends. The paleoclimate information that is being obtained from both caves is complementary and its integration should contribute decisively to the construction of paleoclimate series for Northern Spain.