Introduction

<BODY bgcolor=#ffffff text="#000000" link="#0000ff" vlink="#000088" alink="#00ff00">  <A NAME="tex2html37" HREF="panama-node2_mn.html" TARGET="_top"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="/icon-files//my_next_motif.gif"></A> <A NAME="tex2html33" HREF="panama_mn.html" TARGET="_top"> <IMG WIDTH="27" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="/icon-files//my_up_motif.gif"></A> <A NAME="tex2html27" HREF="panama_mn.html" TARGET="_top"> <IMG WIDTH="67" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="/icon-files//my_previous_motif.gif"></A> <A NAME="tex2html35" HREF="panama-node1_tf.html" TARGET="_top"> <IMG WIDTH="66" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="/icon-files//my_contents_motif.gif"></A> <A NAME="tex2html1" HREF="http://www.erdw.ethz.ch/~bonk/ulis-homepage/" TARGET="_top"><IMG ALIGN="BOTTOM" BORDER="0" SRC="http://www.erdw.ethz.ch/~bonk/icon-files/home.gif" ALT="home.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html38" HREF="panama-node2_mn.html" TARGET="_top">Facies description of the</A> <B> Up:</B> <A NAME="tex2html34" HREF="panama_mn.html" TARGET="_top">Architecture and facies associations</A> <B> Previous:</B> <A NAME="tex2html28" HREF="panama_mn.html" TARGET="_top">Architecture and facies associations</A> &nbsp <B> <A NAME="tex2html36" HREF="panama-node1_tf.html" TARGET="_top">Contents</A></B> <BR> <BR> <H1><A NAME="SECTION00010000000000000000"> Introduction</A> </H1> The Burica Peninsula (Costa Rica/W-Panama) belongs to the forearc area of the Central American arc-trench system which extends along southern Mexico and the Central American isthmus. The southern part of the Central American landbridge is the product of an island arc (<A HREF="panama-node9_ct.html#seyfried" TARGET="contents">Seyfried et al., 1991</A>) and was initially formed in the early Late Cretaceous (<A HREF="panama-node9_ct.html#winsemann93" TARGET="contents">Winsemann, 1993</A>). Detailed descriptions of the forearc basin-fill systems have recently been publishecl by <A HREF="panama-node9_ct.html#kolb" TARGET="contents">Kolb & Schmidt (1991)</A> <A HREF="panama-node9_ct.html#schmidt91" TARGET="contents">Schmidt & Seyfried (1991)</A>, <A HREF="panama-node9_ct.html#winsemann91" TARGET="contents">Winsemann & Seyfried (1991)</A>, <A HREF="panama-node9_ct.html#amann93" TARGET="contents">Amann (1993)</A>, <A NAME="tex2html41" HREF="panama-node9_ct.html#eynatten92" TARGET="contents">Eynatten et al. (1992)</A>; <A NAME="tex2html42" HREF="panama-node9_ct.html#eynatten93" TARGET="contents">Eynatten et al. (1993)</A> and <A HREF="panama-node9_ct.html#winsemann92" TARGET="contents">Winsemann (1992)</A> <P> The plate tectonic configuration is outlined in Fig.<A HREF="panama-node1_ct.html#fig:fig10-1">1</A>. <P></P> <DIV ALIGN="CENTER"><A NAME="fig:fig10-1"></A><A NAME="365"></A> <TABLE> <CAPTION ALIGN="BOTTOM"><STRONG>Figure 1:</STRONG> Plate tectonic configuration modfied after <A HREF="panama-node9_ct.html#mackay" TARGET="contents">MacKay & Moore (1990)</A>. The Cocos Plate is currently being subducted beneath Costa Rica at 9 cm/yr (<A HREF="panama-node9_ct.html#burbach" TARGET="contents">Burbach et al., 1984</A>). The plate boundary between Cocos Plate and Nazca Plate is formed by the Panama Fracture Zone which initially evolved in the late Miocene (<A HREF="panama-node9_ct.html#lowrie79" TARGET="contents">Lowrie et al., 1979</A>). The aseismic Cocos Ridge reached the subduction zone one million years ago and is recently being subducted beneath the Burica Peninsula (<A HREF="panama-node9_ct.html#londsdale" TARGET="contents">Londsdale & Klitgord, 1978</A>). A major strike-slip fault system (partly mentionecl as the Medial Fault Zone by <A HREF="panama-node9_ct.html#corrigan" TARGET="contents">Corrigan et al. (1990)</A> structurally terminates the study area (Burica Peninsula.</CAPTION> <TR><TD><IMG ALIGN="BOTTOM" BORDER="0" SRC="fig10-1.jpg" ALT="204"></TD></TR> </TABLE> </DIV><P></P> Trench-parallel, left-lateral strike-slip movements are considered to be the dominant mechanism in the development of the depositional environments of the study area. The 'Ballena-Celmira Fault Zone' (<A HREF="panama-node9_ct.html#corrigan" TARGET="contents">Corrigan et al., 1990</A>), or the 'Longitudinal Fault' (<A HREF="panama-node9_ct.html#seyfried" TARGET="contents">Seyfried et al., 1991</A>), probably represents the most prominent structural feature north of the Burica Peninsula. Parallel to this active fault, shear movements and related conjugate sets of strike-slip faults have affected the sedimentary sequence. This is documented in lineation geometries obtained from satellite imagery and aerial photographs, in addition to outcrop data analysis. Large strike-slip faults are the main controlling factor of basin geometries. Steeply dipping reverse faults within the Medial Fault Zone' (<A HREF="panama-node9_ct.html#corrigan" TARGET="contents">Corrigan et al., 1990</A>)represent part of a north-south striking positive flower-structure. <P> The basement rocks (Nicoya Complex) consist mainly of T-Morb, N-Morb, IAT and radiolarites, with ages ranging from early Cretaceous to mid-Eocene times (<A HREF="panama-node9_ct.html#seyfried" TARGET="contents">Seyfried et al., 1991</A>). They are overlain by bioclastic and biomicritic limestones of late Palaeocene to Eocene age which are poorly exposed (<A HREF="panama-node9_ct.html#corrigan" TARGET="contents">Corrigan et al., 1990</A>). An at least 3.5 km thick sequence of Pliocene to Pleistocene volcaniclastic marine sediments of the Charco Azul Formation unconformably overlie the basement According to <A HREF="panama-node9_ct.html#corrigan" TARGET="contents">Corrigan et al. (1990)</A>, the Charco Azul Formation can be divided into three members and consists of a basal unit of shallow marine deposits (Penita Member), a middle unit of deep-water deposits (Burica Member) and an upper unit (Armuelles Member) recording the rapid shoaling from deep to shallow water condition In this chapter detailed sections of the llurica Member are presentecl, giving an excellent insight into the architecture of a continuous section of trench slope deposits. <P> <HR>  <A NAME="tex2html37" HREF="panama-node2_mn.html" TARGET="_top"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="/icon-files//my_next_motif.gif"></A> <A NAME="tex2html33" HREF="panama_mn.html" TARGET="_top"> <IMG WIDTH="27" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="/icon-files//my_up_motif.gif"></A> <A NAME="tex2html27" HREF="panama_mn.html" TARGET="_top"> <IMG WIDTH="67" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="/icon-files//my_previous_motif.gif"></A> <A NAME="tex2html35" HREF="panama-node1_tf.html" TARGET="_top"> <IMG WIDTH="66" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="/icon-files//my_contents_motif.gif"></A> <A NAME="tex2html1" HREF="http://www.erdw.ethz.ch/~bonk/ulis-homepage/" TARGET="_top"><IMG ALIGN="BOTTOM" BORDER="0" SRC="http://www.erdw.ethz.ch/~bonk/icon-files/home.gif" ALT="home.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html38" HREF="panama-node2_mn.html" TARGET="_top">Facies description of the</A> <B> Up:</B> <A NAME="tex2html34" HREF="panama_mn.html" TARGET="_top">Architecture and facies associations</A> <B> Previous:</B> <A NAME="tex2html28" HREF="panama_mn.html" TARGET="_top">Architecture and facies associations</A> &nbsp <B> <A NAME="tex2html36" HREF="panama-node1_tf.html" TARGET="_top">Contents</A></B> <HR> <ADDRESS> Schlegel et al., 1996. Architecture and facies associations... <BR><I> Last updated by <A HREF="http://www.erdw.ethz.ch/~bonk/ulis-homepage/" TARGET="_top"> Uli Wortmann</A> 1999-03-09 </I> </ADDRESS>