The NW-Argentinian loess record and its implications for climate history in South America over the past 1.2 Ma
Despite the hypothesized importance of the Central Andes for South American paleoclimatology, very few records from that region extend to periods earlier than the last glacial maximun. Focusing on loess deposits in NW-Argentina, this thesis aimed to broaden the knowledge of long-term Pleistocene cli...
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Bern, Schweisz (Suiza)
Universität Bern, Philosophisch_naturwissenschaftlichen Fakultät, Geographisches Institut
2004
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| 100 | 1 | |a Schellenberger, |b Andreas G. | |
| 245 | 1 | 0 | |a The NW-Argentinian loess record and its implications for climate history in South America over the past 1.2 Ma |
| 264 | 1 | |a Bern, Schweisz (Suiza) |b Universität Bern, Philosophisch_naturwissenschaftlichen Fakultät, Geographisches Institut |c 2004 | |
| 300 | |a v, 209 p. |b il., fot.color, map. |c 29,5 cm. | ||
| 336 | |a texto |b txt |2 rdacontent | ||
| 337 | |a no mediado |b n |2 rdamedia | ||
| 338 | |a volumen |b nc |2 rdacarrier | ||
| 490 | 0 | |a Bibliografía al final de cada capítulo | |
| 490 | 0 | |a Incluye capítulos en inglés y otros en alemán | |
| 490 | 0 | |a nº de orden interno: TDG 46 | |
| 502 | |a TESIS -- Universität Bern, Philosophisch_naturwissenschaftlichen Fakultät, Geographisches Institut -- Doctorado en Geología -- 2004. | ||
| 520 | |a Despite the hypothesized importance of the Central Andes for South American paleoclimatology, very few records from that region extend to periods earlier than the last glacial maximun. Focusing on loess deposits in NW-Argentina, this thesis aimed to broaden the knowledge of long-term Pleistocene climate history in South America. Four thick loess-paleosol sequences in the intramontane Tafí basin (27ºS,66ºW) were studied. Magnetostratigraphical dating in one section gave clear evidence that loess sedimentation started prior to 1.15 Ma. the pleosols indetified range from Calcic Kastanozems to Albic Luvisols and were formed mainly in pedogenic processes of carbonate redistribution, soil aggregate formation, soil organic matter accumulation and clay translocation. A multiproxy approach including sedimentology, soil chemistry and isotope) geochemistry was used to characterize the pedostratigraphic units. Overall geochemical variability is low and largely related to pedogenesis. Our data support the model of a principally Altiplano provenance of NW-Argentinian loess. Variations of magnetic susceptibility and Fe2O3 ratios, that have benn attested good climate proxy indicator quelities with regard to Eurasian loess sequences, failed to provide a quantitative measurement of the degree of pedogenesis in the Tafí sequences.- Due to the topoclimatically-induced high pedodiversity in Tafí valley, the four sections studied vary considerably in their pedosedimentary characteristics. With the aid of marker beds, however, a pedostratigraphic correlation could be established that sharpens paleoclimatic evidence by clearing site-specific response. On this basis, the potential of the pedostratigraphic approach in NW-Argentinian loess is discussed in detail.- The 50-m-thick Las Carreras sequence consists of 32 paleosols. Polarity zonation and tuning the paleosols to climate proxy dat yielded a basal age of > 1.2 Ma. Thus, the section is not only the most complete Quaternary pedostratigraphic section in South America, but also one of the longest continental records in the Southern Hemisphere. Loess-paleosol alternation demonstrates that the study area underwent important changes in effective moisture at orbital timescales, caused by the variability of the South American Monsoon System. Stable carbon isotope ratios of soil organic matter reflect concomitant vegetation dynamics. The pedosedimentary record indicates that environmental changes associated with the mid-Pleistocene transition began at & 1.01 Ma and lasted until &0.72 Ma paleoclimatic evidence suggests that while precessional (low-latitude) forcing of monsoonal climate persisted throughout the entire record, it was superimposed by high-latitude processes primarily affectin SAMS throughout the Pleistocene.- The distinct paleogeoecological changes recorded in NW-Argentinian loess reveal the first long-term history of South American monsoonal climate. The findings of the present study enabled a preliminary evaluation of forcing mechanisms relevant to paleomonsoon variability. It is assumed that further studies in Tafí loess focusing on the validation of a high-resolution climate proxy and the establishment of an independen chronological control will open up new and unexpected paleoclimatic resources for South american Quaternary research | ||
| 650 | 4 | |a GEOLOGIA. |9 FCN-UNT | |
| 650 | 4 | |a CIENCIAS DE LA TIERRA. |9 FCN-UNT | |
| 650 | 4 | |a SEDIMENTOLOGIA. |9 FCN-UNT | |
| 650 | 4 | |a NOROESTE ARGENTINO. |9 FCN-UNT | |
| 650 | 4 | |a PALEOCLIMA. |9 FCN-UNT | |
| 650 | 4 | |a PALEOAMBIENTE. |9 FCN-UNT | |
| 650 | 4 | |a CUATERNARIO. |9 FCN-UNT | |
| 650 | 4 | |a MAGNETOESTRATIGRAFIA. |9 FCN-UNT | |
| 650 | 4 | |a TAFI DEL VALLE. |9 FCN-UNT | |
| 650 | 4 | |a VALLE DE TAFI. |9 FCN-UNT | |
| 650 | 4 | |a TUCUMAN. |9 FCN-UNT | |
| 650 | 4 | |a ARGENTINA. |9 FCN-UNT | |
| 650 | 4 | |a TESIS. |9 FCN-UNT | |
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