%0 Journal Article
%T An¨¢lisis de cadenas de Markov y series de Fourier en una secuencia hemipel¨¢gica del Jur¨¢sico superior de la Pen¨ªnsula Ant¨¢rtica
%A Diego A. Kietzmann
%A Jos¨¦ I. Cuiti£¿o
%A Rub¨¦n A. Medina
%A Roberto A. Scaso
%J Latin American Journal of Sedimentology and Basin Analysis
%D 2009
%I Asociaci¨®n Argentina de Sedimentolog¨ªa
%X La Formaci¨®n Ameghino (Kimmeridgiano-Berriasiano), Cuenca Larsen, Pen¨ªnsula Ant¨¢rtica, est¨¢ compuesta por una asociaci¨®n de microfacies de pelitas con radiolarios (P1), pelitas negras (P2), pelitas bioturbadas y peloidales (P3), tobas (T) y areniscas (A) excelentemente preservadas. Este conjunto de microfacies revela sedimentaci¨®n pel¨¢gica/ hemipel¨¢gica en un ambiente deficiente en ox¨ªgeno, peri¨®dicamente interrumpida por ca¨ªdas de cenizas del arco volc¨¢nico ant¨¢rtico. An¨¢lisis basados en cadenas de Markov indican la recurrencia de las microfacies y sus relaciones c¨ªclicas. Se interpreta que la alternancia de pelitas con radiolarios y pelitas negras (P1-P2) responde a variaciones en la productividad/diluci¨®n, mientras que las microfacies de tobas y areniscas corresponden a dep¨®sitos de evento que modificaron las condiciones ambientales y diagen¨¦ticas evitando la disoluci¨®n de los esqueletos de radiolarios en la masa de agua y en el fondo, y generando de este modo una memoria markoviana con ciclos T-P1-P2. Por otra parte, el an¨¢lisis por transformadas de Fourier indica para los ciclos P1-P2 una duraci¨®n del orden de 1000 a os, en el rango de variaciones sub-Milankovitch. The Upper Jurassic strata of the Larsen Basin, in the northeastern tip of the Antarctic Peninsula (Fig. 1), consist of thin, well-bedded, radiolarian-rich shales, fallout tuffs and volcaniclastic sandstones, grouped in a stratigraphic unit known as Ameghino Formation (or Nordenskj ld Formation for British authors - see Whitham and Doyle, 1989). The Ameghino Formation succession records a fine-grained and high-rate continuous suspensive sedimentation in a quiet hemipelagic environment, with little reworking at the bottom. A 1.3 m-thick representative section for the Upper Member of the Ameghino Formation was sampled bed by bed and studied under petrographic microscopy for microfacies determination. Cyclicity was defined by means of Markov chain analysis and Fourier series (Blackman- Tukey and wavelet methods). Microfacies: The succession is composed of a microfacies association of radiolarianrich shales (P1), black shales (P2), bioturbated and peloidal shales (P3), tuffs (T) and sandstones (A) superbly preserved (Figs. 2 and 3). Sedimentation took place in an oxygen-depleted environment, periodically interrupted by rapid, event-sedimentation mostly caused by large explosive eruptions at the volcanic arc of the Antarctic Peninsula. The P1 and P2 microfacies are interpreted as the result of the deposition from pelagic suspensions during cycles of varying biological productivity or terrigenou
%K Microfacies
%K Cadenas de Markov
%K Series de Fourier
%K Formaci¨®n Ameghino
%K Jur¨¢sico
%K Pen¨ªnsula Ant¨¢rtica
%K Microfacies
%K Markov chains
%K Fourier series
%K Ameghino Formation
%K Upper Jurassic
%K Antarctic Peninsula
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S1851-49792009000100005