Facies model of a deep-water ramp system (Punta Negra Formation) Devonian, Argentine Precordillera

Author(s)

Andre Henrique

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica
• Defense date: 2009-02-16

Examining board members

Giorgio Basilici; Henrique Rosa; Alexandre Campane Vidal

• Advisor: Giorgio Basilici

Abstract

The Punta Negra Formation (Middle to Late Devonian of Argentine Precordillera) is a thick succession of siliciclatic deep-water deposits. This unit outcrops for c. 300 km along north-south direction in the provinces of San Juan, Mendoza and La Rioja. Detailed sedimentological permitted to identify six lithofacies deposited by concentrated density flows and turbidity currents. Three facies associations were described and interpreted: i) channel-filling deposits: massive fine grained sandstone erosive depressions that represent multiple shallow channels in a ramp system; ii) proximal lobes: thickening-upward successions of fine grained massive sandstone beds with a upper portion of very fine laminated sandstone; these beds are amalgamated or interbedded with laminated mudstone and represent depositional lobes in a proximal ramp context; iii) distal lobes/fringe: interstratifications of mudstone and very fine sandstone that are associated to a distal ramp. The channels are constituted of multiple depositional and minor erosional events. The depositional lobes include linguoid bodies with compensation cycles. The fringes have large extension and are characterized by thin interbedding of mudstone/discontinuous very fine sandstone. It was proposed a sand-rich deep-water ramp depositional model, which is characterized by a system of multiple minor erosive channels (multiple source). The immature sediments, the abundance of vegetal fragments and the typical structures of relative long-lived flows evidence a depositional system fed by hyperpicnal flows probably originated of major fluvial floods (AU)