|Titre||Imaging fluvial architecture within a paleovalley fill using ground penetrating radar, Maple Creek, Guyana|
|Auteur||Hickin, A S; Paulen, R C; Bobrowsky, P T|
|Source||Geological Association of Canada-Mineralogical Association of Canada, programs with abstracts; par The Desert Research Institute; Association géologique du Canada-Association minéralogique du Canada,
Réunion annuelle, Programme et résumés 28, 2003 p. 75|
|Liens||Online - En ligne |
|Séries alt.||Secteur des sciences de la Terre, Contribution externe 20080430|
|Réunion||Geological Association of Canada-Mineralogical Association of Canada; Vancouver; CA; mai 26-28, 2003|
|Document||publication en série|
|Sujets||géoradar; méthodes radar; dépôts fluviaux; gisements alluvionnaires; diamant; or; levés géophysiques; géophysique|
|Résumé||(disponible en anglais seulement)|
Direct three-dimensional observation of the sedimentological structure and organization of a valley fill is often difficult. Historically, studies have relied
on either the rock record or modeling and two-dimensional observations of modern fluvial environments. Usually the critical link between subsurface structures, erosional processes and sediment deposition cannot be directly observed. However, recent
development of high-resolution geophysical methods can now bridge this gap by providing the in situ imaging of valley fill sediments.
In late 1999 and early 2000, a total of 44 km of ground penetrating radar (GPR) survey line was collected at
the Vannessa Ventures Ltd.'s Maple Creek diamond and gold placer property in Guyana, South America. Here, the quartz-rich sediment allowed for excellent depth penetration (>40 m) as well as high resolution imaging of the architecture of the fluvial
valley fill sediments.
The processed survey lines clearly imaged a number of discrete architectural elements. The most notable bounding surface is the 6th order bedrock-sediment interface that defines the paleo-bedrock surface. Another
regionally extensive surface is imaged near the top of the profiles and represents either a weathering contact or the sequence boundary between the fluvial valley fill sediments and ubiquitous surface sand. Other examples of architectural elements
present in the GPR profiles are channels, barforms, as well as downstream and lateral-accretion macroforms. Examples of GPR imagery show the internal geometry of a buried valley in a tropical setting. Trenching in the study area has confirmed many of
the major reflectors and provided direct observation of some of the fill elements.