HR: 0800h
AN: PP51D-0627    [Abstracts]
TI: High Resolution Diatom Biostratigraphy for the Past 400 Years From West Pisco Basin, Peru
AU: Tapia, P
EM: perico_tapia@yahoo.com
AF: Universidad Peruana Cayetano Heredia, Laboratorio de palinologia y paleobotanica, Av. Honorio Delgado 430,Urb. Ingenier¡a, S.M.P., 31 Peru
AU: * Gutierrez, D
EM: dgutierrez@imarpe.gob.pe
AF: Direccion de Investigaciones Oceanograficas, Instituto del Mar del Peru, Esquina de Gamarra y General Valle s/n, Chucuito, Callao, 1 Peru
AU: Velazco, F
EM: fvelazco@omarpe.gob.pe
AF: Direccion de Investigaciones Oceanograficas, Instituto del Mar del Peru, Esquina de Gamarra y General Valle s/n, Chucuito, Callao, 1 Peru
AU: Salvatteci, R
EM: rsalvatteci@imarpe.gob.pe
AF: Direccion de Investigaciones Oceanograficas, Instituto del Mar del Peru, Esquina de Gamarra y General Valle s/n, Chucuito, Callao, 1 Peru
AU: Ortlieb, L
EM: Luc.Ortlieb@bondy.ird.fr
AF: UR Paleotropique, Institut de Recherche pour le Developpement, IRD, 32 Henri Varagnat, BONDY, 93143 France
AU: Soler, P
EM: rep-ird@amauta.rcp.net.pe
AF: Institut de Recherche pour le Developpement, IRD, La Mariscala Nø 115 Lima, San Isidro, 27 Peru
AU: Sifeddine, A
EM: Abdel.Sifeddine@bondy.ird.fr
AF: UR Paleotropique, Institut de Recherche pour le Developpement, IRD, 32 Henri Varagnat, BONDY, 93143 France
AU: Baumgartner, T
EM: tbaumgar@cicese.mx
AF: Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, CICESE, Km. 107 Carretera Tijuana, Ensenada, 22860 Mexico
AU: Ferreira, V
EM: paleoc@cicese.mx
AF: Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, CICESE, Km. 107 Carretera Tijuana, Ensenada, 22860 Mexico
AU: Field, D
EM: David.Field@noaa.gov
AF: Fisheries Resources Division, Southwest Fisheries Science Center, La Jolla, 8604 La Jolla Shores Drive, La Jolla, California, 92037-1508 United States
AU: Solis, J
EM: jsolis@imarpe.gob.pe
AF: Direccion de Investigaciones Oceanograficas, Instituto del Mar del Peru, Esquina de Gamarra y General Valle s/n, Chucuito, Callao, 1 Peru
AB: A high-resolution record from box-core B0405-6-IV retrieved off Pisco, south-central Peru, at 300-m water depth shows important diatom species changes during its the time of deposition. An age model based on excess 210Pb activities, bomb-derived 241Am signals, and sediment structures derived from historically well-known seismic events, suggests about 400-yr of sedimentary record. The 73-cm core contains massive and fine to coarse laminated mud; samples for siliceous microfossils analysis were taken continuously every 3 to 8 mm following the main sedimentary structure. Mean sedimentation rate is 2.2 mm x yr-1 in the upper section of the core, which indicate that each sample interval may represent from 1.3 to 3.6 yr. Four diatom assemblages are present throughout the core. Sediments contain Chaetoceros resting spores throughout the whole sequence indicating that the site lies over an active coastal upwelling system. The Chaetoceros group dominates the lower half of the core sediment and define the first diatom assemblage. This assemblage is present in the bottom half of the core from about 73 cm (1600 AD) to 33 cm and contains Actinopthychus senarius, Cocconeis sp., Fragilariopsis doliolus and Thalassiosira eccentrica as subordinated species. Diatom concentrations in the lower half of the core are lower than in the upper part. A second assemblage is found from about 33 cm (1840 AD) to 26 cm, and is dominated by the centric diatom Skeletonema costatum, with Pseudo-nitzschia pungens, Pseudo-nitzschia australis and Prosbocia alata as subdominant species. The third assemblage extends from about 26 cm (1870 AD) to 10 cm and contains abundant Thalassionema bacillare and lower amounts of Coscinodiscus argus. Finally, the last diatom assemblage represent the past 50 years with an important increment of Thalassionema nitzschiodes coupled by the presence of Actinocyclus octonarius as subordinate species. Rare occurrences of freshwater diatoms are found downcore from 25 cm to the bottom, which suggests that the site were reached by particles out of severalpulses of riverine water from the Andes. Decadal to centennial-scale changes on diatom composition from the past 165 years (since 1840 AD) is quite remarkable because a) the diatom species are mostly indicative of modern Cold Coastal Waters, and b) the changes coincide with higher concentrations of diatom valves. This increase of primary productivity on the Peruvian upwelling system is the highest from the last 400-yr record.
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005