Paleoclimate and growth rates of speleothems in the northwestern Iberian Peninsula over the last two glacial cycles

Abstract

Speleothem growth requires humid climates sufficiently warm to stimulate soil CO2 production by plants. We compile 283 U/Th dates on 21 stalagmites from six cave systems in the NW coast of Spain to evaluate if there are patterns in stalagmite growth that are evidence of climatic forcing. In the oldest stalagmites, from marine oxygen isotope stage (MIS) 7–5, growth persists through the glacial period. Hiatuses and major reductions in growth rate occur during extreme minima in summer insolation. Stalagmites active during the last interglaciation cease growth at the MIS 5–4 boundary (74 ka), when regional sea-surface temperature cooled significantly. During MIS 3, only two stalagmites grew; rates were highest between 50 and 60 ka during the maximum in summer insolation. One stalagmite grew briefly at 41 ka, 36.5 and 28.6 ka, all during warm phases of the Dansgaard–Oeschger cycles. A pronounced Holocene optimum in stalagmite growth occurs from 9 to 6 ka. The cessation of most growth by 4.1 ka, coincident with broad increases in aridity over the Mediterranean and areas influenced by the North African Monsoon, suggest that regions such as NW Spain, with dominant Atlantic moisture sources, also experienced increased aridity at this time.

Hydroclimate of the Last Glacial Maximum and deglaciation in southern Australia's arid margin interpreted from speleothem records (23–15 ka)

“…This relationship between enhanced speleothem growth during periods of increased effective precipitation is also observed outside Australia (e.g. Wang et al, 2004;Vaks et al, 2006;Stoll et al, 2013) and highlights stalagmite growth as a useful on/off indicator of recharge in semi-arid to arid environments.…”

A compilation of Western European terrestrial records 60–8 ka BP: towards an understanding of latitudinal climatic gradients

“…However, as speleothem growth is sensitive to climatic conditions, they may form hiatuses during cold and dry phases (Genty et al, 2010). On the other hand, precise determination of the durations of these hiatuses may provide valuable information about climatic thresholds that affect regional climatic conditions (Moreno et al, 2010a;Zhornyak et al, 2011;Stoll et al, 2013).…”

Analytical pyrolysis and stable isotope analyses reveal past environmental changes in coralloid speleothems from Easter Island (Chile)

“…In humid climates or during heavy precipitation a relatively rapid speleothem growth may occur, whereas in arid climates or during drought the growth is moderated or ceased. Hence, the composition, abundance and growth pattern of speleothems may be indicative of climate changes, as reported by several authors [25][26][27][28][29].…”