Diagenesis of the Pennsylvanian –Lower Permian Copacabana Formation, western Bolivian Altiplano

L. M. Nina, A. N. Sial, A. Barbosa, V. H.M. Neumann, G. Bark, R. Garcia, C. Wanhainen, M. Blanco

Research output: Contribution to journalArticlepeer-review

Abstract

This contribution presents the diagenetic evolution of limestone deposits in the Copacabana Formation that occurs in the northern Altiplano, in the Lake Titicaca area of western Bolivia. The best-exposed stratigraphic succession of the Copacabana Formation occurs in the Yampupata section, and its division into five facies successions is based on petrographic analysis, cathodoluminescence, x-ray fluorescence analysis (chemical composition) and stable isotope data (δ18O and δ13C). The results showed that the carbonate rocks experienced early marine diagenetic processes such as micritization during or after the deposition (eogenesis). The initial burial event (mesogenesis 1), characterized by stabilization of temperature-water carbonates by freshwater, and represented by bladed calcite-cement, equant calcite cement, dissolution, dolomitization, neomorphism, silicification and compaction (physical), occurred in shallow burial conditions. During the second burial episode (mesogenesis 2), in deeper burial environment the processes include: compaction (physical and chemical) and neomorphism. Diagenetic processes have affected reservoir quality in the Copacabana Formation during the mesodiagenesis, and reduced the conditions for development of high-quality conventional hydrocarbon reservoirs. Depleted O and C stable isotope signatures indicate that these carbonate rocks deposits underwent both meteoric and burial diagenesis including moderate water-rock interaction.

Original languageEnglish
Article number102540
JournalJournal of South American Earth Sciences
Volume100
DOIs
StatePublished - Jun 2020

Bibliographical note

Funding Information:
We thank Dr. Alcides N. Sial of the Laboratório Núcleo de Estudos Geoquímicos- Labotatório de Isótopos Estáveis ( NEG-LABISE ), Dept. of Geology, Federal University of Pernambuco, Recife, PE, Brazil. This study was supported by the Swedish Development Agency ( SIDA ). We express our gratitude to the Institute of Geology and Environment ( IGEMA ).

Funding Information:
We thank Dr. Alcides N. Sial of the Laborat?rio N?cleo de Estudos Geoqu?micos- Labotat?rio de Is?topos Est?veis (NEG-LABISE), Dept. of Geology, Federal University of Pernambuco, Recife, PE, Brazil. This study was supported by the Swedish Development Agency (SIDA). We express our gratitude to the Institute of Geology and Environment (IGEMA).

Publisher Copyright:
© 2020 Elsevier Ltd

Keywords

  • C isotope
  • Late paleozoic limestone
  • O isotope
  • Titicaca sub-basin

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