Changing depositional environments in the Colombian Fúquene Basin at submillennial time-scales during 284-27 ka from unmixed grain-size distributions and aquatic pollen

Abstract

In a ~60 m long record reflecting the period from 284 ka to 27 ka we analysed grain size distributions (GSD), organic carbon content, and aquatic pollen assemblages at 1-cm increments. The 4768-points time series show with ~60 yr resolution the dynamic history of Lake Fúquene (2540 m alt., 4° N lat.) of the northern Andes during two full interglacial-glacial cycles. GSD show proportions of clay, fine silt, coarse silt, and sand evidencing the location of the sediment source (proximal vs distal) in relation to the drilling site, and available energy to transport sediments in the catchment area. Loss-on-ignition (LOI) values reflect estimates of the abundance of organic matter (OM) in the sediments. Aquatic pollen were grouped into assemblages characteristic of deep water, shallow water, swamp, and wet lake shore environments, reflecting a hydrological gradient sensitive for lake level changes.The End-Member Modelling Algorithm (EMMA) showed that 4 end-members (EMs) explain an optimal proportion (70%) of the observed variation. EMMA is able to unmix GSD of lacustrine sediments in a genetically meaningful way allowing EMs to be interpreted in past depositional and environmental settings. Most unexplained variability is located in the fraction of coarse sediment. OM content was estimated on the basis of LOI data and formed a fifth EM that mainly indicates presence of peat. Changes concur with submillennial-scale variability established in other proxies from this record (Groot et al., 2011). Periods with distinct sediment compositions are 284-243 ka (mainly MIS 8), 243-201 ka (mainly MIS 7), 201-179 ka (mainly MIS 7/6 transition), 179-133 ka (mainly MIS 6), 133-111 ka, (mainly MIS 5e) 111-87 ka (mainly MIS 5d-5b), 87-79 ka (mainly MIS 5a), 79-62 ka (mainly MIS 4), and 62-27 ka (MIS 3) showing sedimentological regimes are climate driven.

Chapter 2

“…Two parallel cores Fq-9 and Fq-10 were drilled to 58 m depth from a floating raft in the centre of the lake (Figure 12). Lithological changes and x-ray fluorescence-based geochemical records of both cores formed the basis to develop the composite core Fq-9C (Bogotá et al, 2011b;Groot et al, 2011;Vriend et al, 2012). The core was sampled at 1 cm increments.…”

“…Pollen zone silt, sand) provided insights into the production of organic matter in the lake and changing energy levels in the sedimentary environment and/or distance to the river inlet (Vriend et al, 2012) (Figure 15) (Supplementary Information 2).…”

Multi-proxy reconstruction of environmental dynamics and colonization impacts in the Mauritian uplands

“…Similar as in the previous period, charcoal is rare and therefore there is no signal of increased fire frequency. Relatively high fractions of clay and sand and lowest fractions of silt indicate marshy conditions where sand-sized particles are easily retained in wet vegetation (Vriend et al, 2012). Local marshy conditions, an increase in organic matter in the sediments, a better preservation of the pollen grains, and the absence of evidence of fire all point to increasing humidity.…”

Recostrução paleoambiental da Floresta Atlântica durante o MIS5-4-3 (98-49 ka) na bacia de Colônia, estado de São Paulo, Brasil

“…• Fase I, foi marcada por uma tendência crescente com alta variabilidade nas concentrações de fragmentos de carvão entre 98-86 ka AP. (Figura 6.2) Em Fuquene, durante o interglacial MIS 5, a sedimentação principalmente composta por sedimentos da fração areia, ricos em matéria orgânica depositados num ambiente pantanoso (VRIEND et al, 2012). Na bacia de Colônia apresentou condições mais quentes e um ambiente predominantemente de turfa, conforme os valores de inc/coh durante o MIS5, e maior entrada de detritos durante os períodos frios ou glaciais.…”

“…Durante o MIS 4, em Fuquene decresce a deposição de matéria orgânica e o lago alcança maior profundidade, esta tendência continua e em 50 ka AP (MIS 3) o lago tornou-se mais profundo, embora com algumas oscilações no nível de água (VRIEND et al,2012).…”