Late glacial and post-glacial deposits of the Navamuño peatbog (Iberian Central System): Chronology and paleoenvironmental implications

The Navamuño peatbog (Sierra de Béjar, western Spain) is a ∼14 ha pseudo-endorheic depression with boundaries defined by a lateral moraine of the Cuerpo de Hombre paleoglacier and fault-line scarps on granite bedrock. The stratigraphy of the Navamuño peatbog system is characterized here using borehole data to a depth of 20 m. An integrated interpretation from direct-push coring, dynamic probing boreholes and handheld auger drillings advances our knowledge of the Navamuño polygenetic infill. Correlating this data with those obtained in other studies of the chronology and evolutionary sequence of the Cuerpo de Hombre paleoglacier has enabled us to establish the sequence of the hydrological system in the Navamuño depression. During the Late Pleistocene (MIS2), the depression was dammed by the Cuerpo de Hombre glacier and fed by its lateral meltwaters, and was filled with glaciolacustrine deposits. The onset of the Holocene in Navamuño is linked to a flat, fluviotorrential plain with episodes of local shallow pond/peat bog sedimentation. This evolutionary sequence is congruent with the age model obtained from available radiocarbon dating, obtaining 19 ages from ∼800 cal yr BP (at depth 1.11 m) to ∼16800 cal yr BP (at depth 15.90–16.0 m). Finally, the sedimentary record enabled interpretation of the environmental changes occurring in this zone during the late glacial (from the Older Dryas to the Younger Dryas) and postglacial (Holocene) stages, placing them within the paleoclimatic context of the Iberian Peninsula and Mediterranean regions

Palaeoenvironmental changes in the Iberian central system during the Late-glacial and Holocene as inferred from geochemical data: A case study of the Navamuño depression in western Spain

The Iberian Central System (ICS) is a clue region to reveal Mediterranean/Atlantic inferences over Iberia. We present a multidisciplinary study from western Spain conducted in the Navamuño depression (ND), covering the last 16.8 ka (cal BP). A reconstruction of the palaeotemperature from the resulting geochemical data highlights four cold and dry intervals, namely, the Oldest Dryas, Older Dryas, Intra-Allerød Cold Period (IACP), and the Younger Dryas, along with warmer intervals: the Bølling (14.7–14 ka) and the Allerød (12.9–12.6 ka); however, the Greenland Interstadial GI-1c (13.4–13.1 ka) is barely distinguishable in the ND. Despite the shortage of biomass to sustain fire, the earliest charcoals are from ~14.4–13.8 ka. Evidence of ash/dust events overprinting the geochemical background starts at ~13.8–12.8 ka. Significant fire activity in the Early Holocene at ~11.7–10.6 ka affected the ND, matching the westernmost ICS data. This period includes short oceanic spells inferred from Cl peaks at ~10.9–10.2 ka and three cold intervals at 11.4, 9.3, and 8.2 ka disrupted the progressive temperature increase. The Mid-Holocene showed a continuously increasing trend towards an arid climate, peaking at 4.2 ka under a pervasive dust influx from North Africa, which has prevailed since almost ~7.9 ka. A prominent volcanic event at ~6.8–5.8 ka is in Navamuño and Roñanzas (Asturias, N Spain; Gallego et al., 2013) identified from heavy metal-rich layer, synchronous with the last known eruption of the Calatrava volcanic field (South-Central Spain; Poblete-Piedrabuena et al., 2019). This volcanic eruption could affect many other regions half north of Iberia. The pervasive presence of oceanic aerosols in the last three millennia (2.8 ka ~ ) allowed the formation of a Cl-rich peat layer during the Ibero-Roman humid period ~2.1 ka, before a changing around ~0.4 ka toward colder and drier conditions at the Little Ice Age (LIA) period.Ministerio de Ciencia, Innovación y UniversidadesAndalusian Office of Economy and KnowledgeSpanish Ministry of Education, Culture, and SportsDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu