Sedimentology and geomorphology of the Rio Madre de Dios from Diamante to Puerto Maldonado, Amazon Basin, Peru / by Erin M. Hemric.
| Author/creator | Hemric, Erin M. author. |
| Other author | Rigsby, Catherine A., degree supervisor. |
| Other author | East Carolina University. Department of Geology. |
| Format | Theses and dissertations |
| Production | 2006. |
| Description | 116 leaves : illustrations (some color), maps (some color) ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Quaternary fluvial sediments comprising three extensive and sedimentologically complex terrace tracts along the Rio Madre de Dios and its tributaries in the Peruvian Amazon preserve a record of aggradation and downcutting related to local complex-response mechanisms, as well as regional climate change. The terraces range in height from ~ 46 m to ~ 5 m above modem river level and represent three distinct phases of deposition and erosion. The oldest and highest terrace (T3) is underlain by sediments of the Upper Neogene Ipururo Formation, fluvial deposits of the Quaternary Madre de Dios Formation, and younger fluvial strata. The sediments that comprise the T1 and T2 fill sequences also record meandering fluvial environments similar to that in the modem river system including channel, point bar, levee, crevasse splay, floodplain, and floodplain lake deposits. Fossil wood is present in channel, point bar, and floodplain deposits in all three terraced sequences, and paleoroots have been preserved in a few point bar and floodplain deposits. Radiocarbon dates from fossil wood allow determination of the depositional history of the sedimentary sequences, the approximate timing of aggradation and downcutting episodes, and the relationship between fluvial history and climate or tectonic change in this portion of the Amazon Basin. Additional data from the neighboring Altiplano has allowed us to reconstruct these aggradation and downcutting events with a higher degree of confidence. The T3 sedimentary sequence was formed by an episode of aggradation that began before 45,000 cal yr BP and was downcut before -29,800 cal yr BP (the date of the oldest sample from T2). Aggradation of the T3 sequence is apparently correlative with an extremely wet period on the Altiplano, marked by deposition of paleolake Minchin. A second episode of aggradation that began before -29,800 cal yr BP formed the T2 sedimentary sequence. |
| Summary | Aggradation of the sediments comprising T2 is apparentlycoralative with another wet period on the Altiplano, marked by deposition of paleolake Ta͠c︣a. This was followed by an episode of downcutting that resulted in the T2 terrace, which ended some time before -6500 cal yr BP (the only date from Tl). Downcutting of T2 may be related to a dry phase on the Altiplano, which is indicated by salt deposition in the Salar de Uyuni and a lowstand of Lake Titicaca. The final episode of aggradation, resulting in deposition of the sediments comprising Tl, must have commenced before -6500 cal yr BP. Downcutting of this sequence resulted in the formation of the Tl terrace. The occurrence of several oscillating dry and wet periods on the Altiplano during this time makes interpretation of the Tl depositional history more difficult, but it may be possible in future studies with additional radiocarbon dates. |
| General note | Presented to the faculty of the Department of Geology. |
| General note | Advisor: Catherine A. Rigsby |
| Dissertation note | M.S. East Carolina University 2006 |
| Bibliography note | Includes bibliographical references (leaves 40-45). |
| Genre/form | dissertations. |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
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