Ambiente sedimentario y procedencia tectónica de depositación de la arenisca basal de la formación Socorro del grupo Ancón (eoceno medio), acantilados del campo Ancón, áreas Ancón y Cacique, Península de Santa Elena
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2018
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
El Grupo Ancón (Eoceno Medio) en la Península de Santa Elena está dividido en cuatro formaciones: Clay Pebble Beds, Socorro, Seca y Punta Ancón y se encuentra sobreyaciendo al Grupo Azúcar del Paleoceno Tardío. La Arenisca Basal de la Formación Socorro del Grupo Ancón ha producido petróleo desde 1911 y es el segundo reservorio más productivo de la Península de Santa Elena. Se definió la composición litológica, mineralógica, ambiente sedimentario, bioestratigrafía y procedencia tectónica de depositación de la Arenisca Basal de la Formación Socorro, en los acantilados del campo Ancón, áreas Ancón y Cacique de la Península de Santa Elena. Se describieron e interpretaron cinco afloramientos de la Arenisca Basal Socorro, quince láminas delgadas y diez muestras bioestratigráficas. Se reconocieron procesos turbidíticos como: secuencias truncadas de Bouma (a; a y b; y a, b y c), truncadas incompletas (b y c) e incompletas (e y b); bases erosiónales, depositación granodecreciente y acuñamientos (canales turbidíticos).
Los foraminíferos plantónicos (Clavigerinella akersi) del afloramiento BS2 determinaron la edad relativa Eoceno Medio para la Grauvaca Basal Socorro como; y el ambiente de depositación como Marino de Plataforma Interna por la abundancia de radiolarios (Spumellario thecosphaera sp., Spumellario phacodiscus sp.) y foraminíferos bentónicos (lagena sp., Cibicidoides tuxpanensis tuxpanensis, Bulimina prolixa, y Uvigerina yazonensis), sin embargo se encontraron microfósiles de ambientes de talud y llanura abisal. Las areniscas de Socorro y de Clay Pebble Beds son grauvacas feldespáticas: cuarzo 71,73 %, feldespatos 25,21 % y fragmentos líticos 2,91 %; evidenciando un predominio del cuarzo. Diagramas ternarios de procedencia tectónica indican un ambiente Continental Transicional con tendencia hacia cratón interior para la Grauvaca Basal y grauvacas de la Formación Clay Pebble Beds.
The Ancón Group (Middle Eocene) in the Santa Elena Peninsula is divided into four formations: Clay Pebble Beds, Socorro, Seca and Punta Ancón and is overlying the Azucar Group of the Late Paleocene. The Basal Sandstone of the Ancon Group's Socorro Formation has produced oil since 1911 and is the second most productive reservoir of the Santa Elena Peninsula. The lithological composition, mineralogy, sedimentary environment, biostratigraphy and tectonic origin of the Basal Sandstone of the Socorro Formation were defined in the Ancón field cliffs, Ancón and Cacique areas of the Santa Elena Peninsula. Five outcrops of the Basal Socorro Sandstone, fifteen thin sections and ten biostratigraphic samples were described and interpreted. Turbiditic processes were recognized as truncated sequences of Bouma (a, a and b, and a, b and c), incomplete truncated (b and c) and incomplete (e and b); erosional bases, fining-upward deposition and lateral pinch out (turbiditic channels). The plantonic foraminifera (Clavigerinella akersi) of outcrop BS2 determined a relative age of Middle Eocene for the Greywacke Basal Socorro; and the deposition environment as an Internal Marine Platform because of the abundance of radiolarians (Spumellario thecosphaera sp., Spumellario phacodiscus sp.) and benthic foraminifera (lagena sp., Cibicidoides tuxpanensis tuxpanensis, Bulimina prolixa, and Uvigerina yazonensis), however were found Microfossils of slope and abyssal plain environments. The sandstones of Socorro and Clay Pebble Beds are feldspathic greywackes: quartz 71.73%, feldspar 25.21% and lithic fragments 2.91%; showing a predominance of quartz. Ternary diagrams applied for tectonic origin indicate a Transitional Continental environment with a tendency towards craton interior for the Greywacke of Basal Socorro and Clay Pebble Beds Formation.
The Ancón Group (Middle Eocene) in the Santa Elena Peninsula is divided into four formations: Clay Pebble Beds, Socorro, Seca and Punta Ancón and is overlying the Azucar Group of the Late Paleocene. The Basal Sandstone of the Ancon Group's Socorro Formation has produced oil since 1911 and is the second most productive reservoir of the Santa Elena Peninsula. The lithological composition, mineralogy, sedimentary environment, biostratigraphy and tectonic origin of the Basal Sandstone of the Socorro Formation were defined in the Ancón field cliffs, Ancón and Cacique areas of the Santa Elena Peninsula. Five outcrops of the Basal Socorro Sandstone, fifteen thin sections and ten biostratigraphic samples were described and interpreted. Turbiditic processes were recognized as truncated sequences of Bouma (a, a and b, and a, b and c), incomplete truncated (b and c) and incomplete (e and b); erosional bases, fining-upward deposition and lateral pinch out (turbiditic channels). The plantonic foraminifera (Clavigerinella akersi) of outcrop BS2 determined a relative age of Middle Eocene for the Greywacke Basal Socorro; and the deposition environment as an Internal Marine Platform because of the abundance of radiolarians (Spumellario thecosphaera sp., Spumellario phacodiscus sp.) and benthic foraminifera (lagena sp., Cibicidoides tuxpanensis tuxpanensis, Bulimina prolixa, and Uvigerina yazonensis), however were found Microfossils of slope and abyssal plain environments. The sandstones of Socorro and Clay Pebble Beds are feldspathic greywackes: quartz 71.73%, feldspar 25.21% and lithic fragments 2.91%; showing a predominance of quartz. Ternary diagrams applied for tectonic origin indicate a Transitional Continental environment with a tendency towards craton interior for the Greywacke of Basal Socorro and Clay Pebble Beds Formation.