Macrofossils in Raraku Lake (Easter Island) integrated with sedimentary and geochemical records: towards a palaeoecological synthesis for the last 34,000 years

QUATERNARY SCIENCE REVIEWS

卷:34

Review

Canellas-Bolta, N.^1,2  Rull, V.²  Saez, A.¹  Margalef, O.³  Giralt, S.³  Pueyo, J. J.⁴  Birks, H. H.^5,6  Birks, H. J. B.^5,6,7,8  Pla-Rabes, S.⁹ 

[1] Univ Barcelona, Dept Stratig Paleontol & Marine Geosci, E-08028 Barcelona, Spain

[2] Bot Inst Barcelona IBB CSIC ICUB, Lab Palynol & Paleoecol, E-08038 Barcelona, Spain

[3] Inst Earth Sci Jaume Almera ICTJA CSIC, E-08028 Barcelona, Spain

[4] Univ Barcelona, Dept Geochem Petrol & Geol Prospecting, E-08028 Barcelona, Spain

[5] Univ Bergen, Dept Biol, N-5020 Bergen, Norway

[6] Bjerknes Ctr Climate Res, NO-5020 Bergen, Norway

[7] UCL, Environm Change Res Ctr, London WC1E 6BT, England

[8] Univ Oxford, Sch Geog & Environm, Oxford OX1 3QY, England

[9] Ctr Adv Studies Blanes CEAB CSIC, E-17300 Blanes, Spain

关键词: Rapa Nui;    Palaeolimnology;    Taphonomy;    Macrofossils;    Geochemistry;    Sedimentary facies;    Last glacial period;    Holocene;   

DOI  :  10.1016/j.quascirev.2011.12.013

来源: Elsevier

【 摘 要 】

Macrofossil analysis of a composite 19 m long sediment core from Rano Raraku Lake (Easter Island) was related to litho-sedimentary and geochemical features of the sediment. Strong stratigraphical patterns are shown by indirect gradient analyses of the data. The good correspondence between the stratigraphical patterns derived from macrofossil (Correspondence Analysis) and sedimentary and geochemical data (Principal Component Analysis) shows that macrofossil associations provide sound palaeolimnological information in conjunction with sedimentary data. The main taphonomic factors influencing the macrofossil assemblages are run-off from the catchment, the littoral plant belt, and the depositional environment within the basin. Five main stages during the last 34,000 calibrated years BP (cal yr BP) are characterised from the lithological, geochemical, and macrofossil data. From 34 to 14.6 cal kyr BP (last glacial period) the sediments were largely derived from the catchment, indicating a high energy lake environment with much erosion and run-off bringing abundant plant trichomes, lichens, and mosses into the centre of Raraku lake. During the early Holocene the infilling of the lake basin and warmer conditions favoured the growth of a littoral plant belt that obstructed terrigenous input. Cladoceran remains and Solanaceae seeds are indicative of reduced run-off and higher values of N and organic C indicate increased aquatic and catchment productivity. From 8.7 to 4.5 cal kyr BP a swamp occupied the entire basin. The increase of Cyperaceae seeds reflects this swamp development and, with oribatid mites and coleopteran remains, indicates a peaty environment and more anoxic conditions in Raraku. At around 4.5 cal kyr BP dry conditions prevented peat growth and there is a sedimentary hiatus. About 800 cal yr BP, peat deposition resumed. Finally, in the last few centuries, a small lake formed within the surrounding swamp. Evidence of human activity is recorded in these uppermost sediments. (C) 2011 Elsevier Ltd. All rights reserved.

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