Evolution of the northern Argentine margin during the Cenozoic controlled by bottom current dynamics and gravitational processes

Abstract

A detailed reflection seismic investigation on sediment deposition at the northern Argentine margin (37°S to 42°S) resolves major modifications in oceanographic circulation during the Cenozoic, which resulted from variations in both climatic and tectonic processes. After an extensive erosional period following the onset of glaciation of Antartica at ~34 Ma, which affected all water depth levels, a buried elongated mounded drift within the continental shelf was shaped by bottom current activity during the Miocene. This may represent the earliest deposits of the Malvinas Current that branches from the Antartic Circumpolar Current and today is part of a complex shallow water circulation system known as the Brazil-Malvinas confluence. At the same time a major terrace grew to its present form on the upper slope indicating that a precursor of Antarctic Intermediate Water was also part of the BrazilMalvinas confluence. After another major erosional phase inferred from a seismic unconformity at ~6 Ma, sheeted drifts, mounded drifts and sediment waves formed at the continental rise during the Pliocene/Pleistocene. These extensive contourite deposits are diagnostic for a steady north setting bottom flow at the depth level of todays Antarctic Bottomwater. Evidence for downslope transport mainly stems from the presence of buried turbidites and canyon related depocenters. These features can be related to Andean uplift during the Eocene and to the activation of the canyon system during the Pliocene.

The Influence of Climate on the Dynamics of Mountain Building Within the Northern Patagonian Andes

“…The Miocene synorogenic units are covered by a thin carpet of piedmont and glaciofluvial gravel deposits and by widespread basaltic lava flows. In contrast, the upper Miocene—lower Pliocene constitutes an aggradational period that is particularly well developed in the Argentine continental margin (Figure 14; Ercilla et al., 2019; Ghiglione et al., 2016; Gruetzner et al., 2016). The sediment eroded from the interior of the range likely bypassed Patagonia and reached the offshore basins, where they are represented by thick sequences with high sedimentation rates (Gruetzner et al., 2016).…”

“…In contrast, the upper Miocene—lower Pliocene constitutes an aggradational period that is particularly well developed in the Argentine continental margin (Figure 14; Ercilla et al., 2019; Ghiglione et al., 2016; Gruetzner et al., 2016). The sediment eroded from the interior of the range likely bypassed Patagonia and reached the offshore basins, where they are represented by thick sequences with high sedimentation rates (Gruetzner et al., 2016). This regional reorganization of the sediment routing pattern includes evidence of diminished foreland subsidence and can be interpreted as the result of progressive foreland abandonment and sediment bypass during reduced activity on thrust faults (Figure 15).…”

“…Plate kinematic data from Maloney et al (2013). Rates of sedimentation at the Argentine margin from Gruetzner et al (2016). Al, Alicura; Ba, Bandurial; Ca, Caleufu; Esq, Esquel; FG, Fria de los Guanacos; Ga, Gastre; LC, Las Coloradas anticline; LE, La Esperanza; Ma, Cordón del Maitén; PP, Piedra Pintada; PS, Pino Solo; Tr, Taquetrén.…”

IODP workshop: developing scientific drilling proposals for the Argentina Passive Volcanic Continental Margin (APVCM) – basin evolution, deep biosphere, hydrates, sediment dynamics and ocean evolution

“…Drifts are also present farther north along the margin (e.g., Hernández-Molina et al, 2015) with drifts apparently associated with flows of Antarctic Intermediate Water (AAIW), Upper Circumpolar Deep Water (UCDW), North Atlantic Deep Water (NADW), Lower Circumpolar Deep Water (LCDW) and Antarctic Bottom Water (AABW). Violante et al (2010) and Grützner et al (2011Grützner et al ( , 2012Grützner et al ( , 2016 suggested that increased sediment flux to the margin during the Miocene may in part be related to an uplift in the Andes that in turn is due to increased Miocene Pacific Ocean crustal spreading and subduction rates, which peaked at about 10 to 20 Ma (Pardo-Casas and Molnar, 1987;Martinod et al, 2010). However, the routes or processes by which…”

“…However, a number of papers published since 2009 reported new high-resolution and/or multichannel seismic surveys (Fig. 4), often combined with multi-beam bathymetric data, which show the common occurrence of layered sediments and prominent sediment drifts on the Argentine and adjacent Uruguayan margins (e.g., Hernández-Molina et al, 2009Violante et al, 2010, Krastel et al, 2011Lastras et al, 2011;Muñoz et al, 2012;Grützner et al, 2011Grützner et al, , 2012Grützner et al, , 2016Preu et al, 2012Preu et al, , 2013Voigt et al, 2013;Uenzelmann-Neben et al, 2016; see also Hinz et al, 1999). There has also been significant progress studying the climatic records in surficial and near-surface sediments recovered in sediment cores from the Argentine margin (e.g., Chiessi et al, 2007;Bozzano et al, 2011;Govin et al, 2012;Bender et al, 2013;Razik et al, 2013;Razik, 2014;García Chapori et al, 2014, demonstrating that this margin also contains important modern sedimentary deposits.…”