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From Bureau
of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
AAPG Annual Convention, Calgary, Alberta, Canada, June 19–22, 2005 Deepwater Facies Architecture and Evolution of Middle and Lower Miocene Minibasins in the Onshore Salina Basin, Southeastern Mexico Abstract: Lower Neogene minibasins in the onshore part of the Salina Basin in southeastern Mexico were associated with episodic, northward salt mobilization and withdrawal. These minibasins are penetrated by few wells and are relatively unexplored. They are characterized by cyclic deposition of upper-slope turbidites and debris-flow deposits sourced from the Chiapas Fold Belt to the south. Middle Miocene sandy slope-channel facies in the Ogarrio area are 10- to 15-m, upward-fining successions of porous, fine- to medium-grained, crossbedded and plane-bedded sandstone with subangular clay clasts and poorly sorted organic fragments at the base. These channel deposits are flanked by thin (<5-cm scale), rippled and laminated, low-porosity, very fine grained sandstones interbedded with burrowed siltstone. The sparsely drilled lower Miocene
minibasin fill is interpreted to contain numerous intrabasin unconformities
that underlie dim-amplitude, 70- to 120-m, chaotic seismic facies. These
chaotic zones are interpreted to be muddy debris-flow and slump deposits,
similar in seismic character and geometry to those of Pliocene strata
in the Auger minibasin in offshore Louisiana. These lower Miocene chaotic
zones are overlain by relatively thin, bright-amplitude, single-cycle
zones, typically 20 to 40 m thick. These bright-amplitude zones, extremely
continuous, are interpreted to represent potentially sandy turbidite lobe
and sheet deposits. The overall minibasin fill is relatively dim amplitude
updip to the south, whereas bright amplitudes are more common downdip
northward, indicating a muddy bypass slope system grading into sandier,
ponded turbidite facies into the basin. |