Palynofacies analysis and organic-walled dinoflagellate cysts in late-Holocene sediments from Igaliku Fjord, South Greenland

Abstract

This study characterizes late-Holocene (past 3300 years) variations in organic matter deposition in the outer part of Igaliku Fjord, South Greenland, and uses this information to assess palaeohydrographic conditions. Except for two, all residues were characterized by abundant organic matter, with amorphous material dominating. The late-Holocene sediments in the deeper parts of the outer Igaliku Fjord have generally been deposited under anoxic to suboxic conditions with relatively low terrestrial/freshwater influx. The organic-walled dinoflagellate cyst assemblages suggest the continuous presence of water masses derived from the East Greenland Current, while changes in sea-surface temperature during the last 3300 years have also been interpreted. Terrestrial influx was reflected by the continuous occurrence of leaf tissue, which increased in abundance in sediments younger than ad 960. Pseudo-amorphous phytoclasts occurred in sediments older than ad 770, and sporomorphs were rare throughout.Acritarchs and organic-walled dinoflagellate cysts dominated the assemblages in the sediments. Relatively high amounts of benthic foraminiferal linings in the interval ad 960–1285 suggests increased nutrient availability, which may be ascribed to strong, wind-induced mixing of the water-column or higher fluxes of organic material. Sparse organic matter was recorded in sediments of age c.AD 1125 pointing to significant oxidation due to highly oxic bottom-water conditions.