Late Weichselian and Holocene environments of lake Endletvatn, Andoya, 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-bas in of lake Endletvatn was analysed lithologically, palynologically and chem ically. 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 lithost ratigraphical units can be distinguished, which also differ substantially i n chemical characters. Five chemostratigraphical main units were distinguis hed. The two lowermost units 1-2 (18.5-12.9 ka BP) correspond to the lower lithostratigraphical main unit and are characterized by minerogenous sedime nts 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) culmin ating in the early part of the Younger Dryas, indicating abundant N availab le for bio-production. The Fe, Mg, and K content is still high, but decreas ing, indicating decreasing glacial and kryogenic erosion and allogenic depo sition until c. 10.5 ka BP. A hiatus represented by a sand layer covers mos t 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 pr onounced 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, increas ing 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 youn ger than 12.9 ka BP characterizes the sediments as transitional between gyt tja and dy. The Holocene lake type varied between weakly oligohumic and mes ohumic. Stagnant bottom waters (reducing conditions) occur in the periods 1 2.9-11.5 ka BP and c. 7.5-5.3 ka BP. The climatic development and other env ironmental implications of the joint chrono-, chemo-, litho- and biostratig raphical data set are discussed.