[Geoinfo] conferencia Dr. Archer en Buenos Aires

[José Ignacio Cuitiño]

La Asociación Argentina de Sedimentología y el Departamento de Ciencias Geológicas de la UBA tienen el agrado de invitar a la conferencia del Dr. Allen W. Archer:
 
 
"TIDAL RHYTHMITES IN MODERN AND ANCIENT HYPERTIDAL ESTUARIES"
 
 
Lugar: Aula Amos del Departamento de Ciencias Geológicas, FCEyN, UBA. Ciudad Universitaria, Pabellón II. Ciudad Autónoma de Buenos Aires.
 
Fecha: Viernes 19 de Marzo, 14 hs.
 
 
El Dr. Allen W. Archer (PhD University of Indiana) es actualmente profesor de Estratigrafía y Sedimentología en la Univesidad de Kansas, USA. Se ha especializado en ciclicidad y ritmicidad en depósitos originados por mareas (tidal rhythmites), de edades que van desde el Precámbrico hasta el presente, particularmente en estuarios con rangos de mareas extremos.
 
 
Resumen de la conferencia:
Tidal rhythmites, which exhibit systematic variations in lamina thickness, are most common in hypertidal estuaries. Modern examples include the Bay of Fundy in eastern Canada (tidal range >13 m), Ungava Bay in northeastern Canada (>12 m), Bay of Mont Saint Michel in France (>11.5 m), estuaries along the Atlantic coast of southern Argentina (>11 m), and Cook Inlet in south-central Alaska, USA (>10 m). These modern examples provide analogs for ancient rhythmites, which have been documented from the Proterozoic and Phanerozoic eons. Within the spectrum of astronomically forced cycles, short-term periods exhibited by tidal rhythmites include semi-daily, daily, half lunar month (neap-spring), and several lunar monthly cycles. All of these periodicities have been reported from modern and ancient of tidal rhythmites. Short-term tidal periods have quite consistent magnitude and frequency and thus can directly affect sedimentation. Over geologic time, however,
 tidal periods have changed. Examples of very ancient rhythmites indicate that the paleotidal day was significantly shorter and that there were more solar days per year. The rates of sedimentation within hypertidal estuaries can be very high, particularly in the fluvio-estuarine transitional zones. Because of the high turbidity and high sedimentation rates, sediment reworking by the biota can be limited. Thus, bioturbation is minimal. These deposits are dominated by physical sedimentary structures, such as tidal bedding, ripples, and thin laminae. 


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