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Forearc uplift rates deduced from sediment cores of two coastal lakes in south-central Chile
Stefer, S.; Moernaut, J.; Melnick, D.; Echtler, H. P.; Arz, H.W.; Lamy, F.; De Batist, M.; Oncken, O.; Haug, G.H. (2010). Forearc uplift rates deduced from sediment cores of two coastal lakes in south-central Chile. Tectonophysics 495(1-2): 129-143. dx.doi.org/10.1016/j.tecto.2009.05.006
In: Tectonophysics. ELSEVIER SCIENCE BV: New York; London; Amsterdam. ISSN 0040-1951, more
Peer reviewed article  

Available in  Authors 
    VLIZ: Open Repository 227428 [ OMA ]

Keyword
    Marine
Author keywords
    Forearc tectonics; Uplift rate; Lago Lanalhue; Lago Lleu Lleu; Arauco Peninsula; Sea-level change

Authors  Top 
  • Stefer, S.
  • Moernaut, J., more
  • Melnick, D.
  • Echtler, H. P.
  • Arz, H.W.
  • Lamy, F.
  • De Batist, M., more
  • Oncken, O.
  • Haug, G.H.

Abstract
    The present paper introduces a newapproach for deriving information about local forearc tectonics and related uplift rates based on the study of lake sediments.We investigated two coastal lakes at the south-central Chile margin, lakes Lanalhue and Lleu Lleu, located south of the Arauco Peninsula (38°S). Both lakes developed within the valleys of ancient rivers that once drained to the Pacific Ocean, being subsequently dammed by rising sills in the late Pleistocene/early Holocene. Seismic profiling and sedimentological analyses of cores from both lakes revealed similar successions consisting of marine to brackish sediments covered by lacustrine deposits. Radiocarbon dating indicates that the marine–lacustrine transition occurred at 8 ka and 8.15 ka, respectively. The correlation of this transition with global sea-level curves allowed the calculation of local uplift rates for the Holocene.Uplift rates for the lake basins amount to 0.42±0.71 and 0.49±0.44 mm/a, respectively, which are consistent with rates determined from a late Pleistocene marine terrace in the area. However, conspicuously higher, though likely transient, vertical movements at 8.83±2.7 mm/a and 11.36±1.77 mm/a, respectively, were calculated for the sills that block both lakes nowadays. These barriers are interpreted to be the surface expression of a blind reverse fault associated to the Morguilla fault system, a seismically-active structure that controls uplift and folding along the adjacent Arauco Peninsula.

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