Mineralogical proxies of a Pliocene maar lake recording changes in precipitation at the Camp dels Ninots (Pliocene, NE Iberia)

The sedimentary record of the maar lake succession at Camp dels Ninots (Pliocene, NE Spain) reflects mineralogical shifts that correlate with orbitally forced climate changes. X-ray powder diffraction was obtained from a 47 m-long core collected from a borehole drilled in the centre of the paleolake. The results show compositional variations in terms of allogenic/authigenic mineral assemblages which, in turn, correlate with climate proxies such as pollen. Intervals that are dominantly composed of allogenic minerals (quartz, feldspar, smectite) correlate with wet periods. These periods are characterised by an increase in the percentage of Abies pollen. Conversely, intervals enriched in carbonates correlate with dry periods, with decreased amounts of Abies pollen. This cyclicity is attributed to rainfall variations leading to hydrologically open lake conditions during periods of relative high precipitation (when clastic input is enhanced) and hydrologically closed lake conditions during drier periods (when precipitation of authigenic carbonates is enhanced). It is concluded that the mineralogy of maar paleolakes may be highly sensitive to record climate changes.