Post-glacial evolution of alpine environments in the western Mediterranean region: The Laguna Seca record

In an effort to understand how alpine environments from the western Mediterranean region responded climate variations since last glacial-interglacial transition, a detailed chronological control and sedimentological analysis, supported by magnetic susceptibility, total organic carbon C/N data, were carried out on sedimentary record of Laguna Seca (LS). This is latitudinal altitudinally (2259 masl) key wetland site located in easternmost area Sierra Nevada, southern Iberian Peninsula, where sediments accumulated during Heinrich Stadial 1, Bølling-Allerød (B-A) Younger Dryas (YD) - previously unrecorded Nevada. Climate controlled sedimentation LS three coarse-grained one fine-grained facies association are differentiated, which help us decipher paleoenvironmental evolution LS: (1) subaerial cohesionless debris flows paraglacial stage; (2) till or nival diamicton small glacier/nivation hollow (3) massive mudstone suspension settling clays into standing water lacustrine (4) frost-shattering breccia deposited inside stage, probably YD, linked periglacial substage. The development existing glacial cirque Last Glacial Maximum (LGM) basin at elevation between 2500 2300 m could be important availability slope glacially-conditioned such as flows, reworked processes first deglaciation stages, confirming previous studies landforms catchment LGM-Equilibrium Line Altitude estimation above 2400 masl Mean sediment accumulation rates units (4.21 0.28 mm/yr stage respectively) confirm that geomorphic activity accelerated just after glaciers retreated due adjustment high glacially conditioned sediments. An abrupt change paleoclimatic conditions occurred ∼ 15.7 cal kyr BP. was increase temperature precipitation B-A. At LS, this resulted significant ice-melt, forming deep-water lake with matter contribution until end Early Holocene (except YD when level dropped), but elsewhere general glacier recession Nevada expansion forest Peninsula. Finally, long-term aridification Middle present triggered environmental transforming ephemeral aquatic productivity.