Late Weichselian and Holocene environments of lake Endletvatn, Andφya, northern Norway: as evidenced primarily by chemostratigraphical data

A 6.5 m long sediment succession (18.5‐2.2 ka BP) from the northern sub‐basin of lake Endletvatn was analysed lithologically, palynologically and chemically. The chemical analyses were performed at about 10 cm depth intervals for the following parameters: total organic C, N, P, Fe, Mn, Mg, Na, K, Ca and S, in addition to water content, dry density, and pH. Two main lithostratigraphical units can be distinguished, which also differ substantially in chemical characters. Five chemostratigraphical main units were distinguished. The two lowermost units 1–2 (18.5–12.9 ka BP) correspond to the lower lithostratigraphical main unit and are characterized by minerogenous sediments with low C and N, and high Fe, Mg and K. P is low, partly because of a scarcity of P in parent rocks. Chemostratigraphical unit 3 (12.9‐9.6 ka BP) is characterized by increasing C and N and a high N/P ratio (10–20) culminating in the early part of the Younger Dryas, indicating abundant N available for bio‐production. The Fe, Mg, and K content is still high, but decreasing, indicating decreasing glacial and kryogenic erosion and allogenic deposition until c. 10.5 ka BP. A hiatus represented by a sand layer covers most of the time‐span 10.5–9.6 ka BP. Chemostratigraphical unit 4 (9.6‐5.3 ka BP) represents the Holocene thermal optimum in three subunits. In the time interval 9.6–9.1 ka BP, Fe, Mg and K decrease to a minimum and P shows a pronounced increase. The megathermal period c. 8200‐5300 BP, is characterized by maxima of C, N and P and a minimum of Fe. The katathermal period after 5.3 ka BP is characterized primarily by increased Fe precipitation, increasing Fe/Mn ratio, and P, C and N at a constantly lower level than during the megathermal. A stable C/N ratio of about 10, of the sediment interval younger than 12.9 ka BP characterizes the sediments as transitional between gyttja and dy. The Holocene lake type varied between weakly oligohumic and mesohumic. Stagnant bottom waters (reducing conditions) occur in the periods 12.9–11.5 ka BP and c. 7.5‐5.3 ka BP. The climatic development and other environmental implications of the joint chrono‐, chemo‐, litho‐and biostratigraphical data set are discussed.