Using Fluvial Cyclicity To Decipher the Interaction of Basement- and Fold-Thrust-Belt Tectonics In A Broken Foreland Basin: Vinchina Formation (Miocene), Northwestern Argentina

Abstract

The Miocene Vinchina Formation is made up of more than 5100 meters of siliciclastic sediments deposited mostly in fluvial environments in a broken foreland basin without any connection with the sea during a period of arid to semiarid climatic conditions. Repetitive changes in fluvial facies allow the subdivision of the formation into seven cyclothems, each floored by a subaerial unconformity. Within-sequence changes in fluvial systems determined by the proportion of channel vs floodplain, multi-story vs single-story channels, and channel connectedness were controlled by changes in accommodation. Proximal (i.e., northern and younger) sequences show transitions from braided to low-sinuosity (wandering) or high-sinuosity (meandering) fluvial systems, whereas more distal sequences (southern and older) show changes from sand-bed dominated to anastomosed systems. Bounding unconformities and facies stacking patterns are used to define six third-order depositional sequences.Depositional sequences in the Vinchina Formation are either asymmetrical showing a fining-upward trend or nearly symmetrical (sand clock type). Each cyclothem is bounded by an incision surface (sequence boundary) developed during a baselevel (i.e., fluvial equilibrium profile) fall and initial base-level rise floored by basal coarse-grained deposits representing the low-accommodation systems tract (LAST). The overlying sediments fine upward and contain both isolated and multistory sandstone bodies within extensive flood-plain deposits corresponding to the early high-accommodation systems tract (HAST). This interval is sometimes capped by sheets of amalgamated sandstones corresponding to the late HAST and developed during a decline in the rate of base-level rise. The development and/or preservation of the capping amalgamated sandstones and therefore the symmetrical shape of the sequences is favored in high-accommodation settings. Vertical and lateral facies changes recorded in the Vinchina Formation indicate that both the fold-and-thrust belt located to the west and an uplifted basement block to the north played important roles controlling subsidence, source areas, and drainage patterns. The stratigraphic record of this broken foreland basin differ from the existing models for ¨simple¨foreland basins and can be compared to those of the Laramide sedimentary basins in the United States.

U-Pb ages of detrital and volcanic zircons of the Toro Negro Formation, northwestern Argentina: Age, provenance and sedimentation rates

“…However, other basement blocks were uplifted earlier in the Miocene. For example, the Vinchina basin was already receiving sediments from the Toro Negro basement uplift as early as 15 Ma (Marenssi et al, 2015) and the Sierra de Famatina to the east had already experienced uplift during the early and middle Miocene (Dávila and Astini, 2007). It is thus conceivable that the deep localized incision of the Vinchina formation (the basal unconformity) was driven by uplift along basement structures in the immediate vicinity of the Vinchina basin.…”

“…By ~6.5 Ma, uplift of the SierrasPampeanasfragments the Bermejo foreland into more localized depocenters (Jordan et al, 2001).As additional studies have focused on these localized depocenters, it has become clear that some of the basement uplifts, particularly those in the north, such as the Vinchina Basin, are older and record a complex interplay of thin-and thickskinned deformation throughout the Miocene (e.g. Dávila and Astini, 2007;Ciccioli et al, 2011Ciccioli et al, , 2013aMarenssi et al,2015). Thus, many questions remain about the precise spatio-temporal pattern with which the broken foreland evolved,and how it was controlled by pre-existing structures and changes in the Pacific-South America plate dynamics.…”

“…The sedimentology of the Vinchinadepocenter has been well studied over the past 10 years (e.g. Tripaldi et al, 2001;Limarino et al, 2001;Ciccioli, 2008;Ciccioli and Marenssi, 2012;Ciccioli et al, 2011Ciccioli et al, , 2013bCiccioli et al, , 2014aMarenssi et al, 2015).In particular, the modal composition of sandstones and conglomerates has proven an effective means to establish source areas and to explorethe relation between shifts in compositional framework and changes in watershed configuration (Ciccioli, 2008;Ciccioli et al, 2014a). Sandstone composition does not, however, depend exclusively on the source rocks: it may be affected by the physiography and chemical weathering in the source area, by reworking and abrasion of the sediments during transportation and sedimentation, by recycling of older sediments, and by diagenetic effects (Amorosi and Zuffa, 2011;Dickinson and Suczek, 1979;Espejo and Lopez-Gamundi, 1994).…”

Sediment Storage Partitioning in Alluvial Stratigraphy: The Influence of Discharge Variability

“…Information about temporal trends in the channel to overbank sediment ratio of a river's deposit can provide important context to stratigraphic reconstructions across climate boundaries (e.g., Foreman et al 2012), and could factor in to global predictions of fluvial response to climate change (Toonen et al 2017). Further, sequence stratigraphic reconstructions of alluvial successions along continental margins (e.g., Huerta et al 2011;Marenssi et al 2015) will be improved by considering hydrograph variability in the context of the existing allogenic forcings of accommodation and sediment supply. We also note that the role of overbank environments as sinks for fine-grained sediments makes them important to the global carbon cycle (Sutfin et al 2016), and our results imply that changes to regional precipitation patterns in response to global climate change (e.g., Scholes et al 2014) could influence terrestrial carbon budgets.…”

Evolution of a patagonian Miocene intermontane basin and its relationship with the Andean foreland: Tectono-stratigraphic evidences from the Catán Lil Basin, Argentina

“…Aggradational/ degradational cycles could be explained in terms of tectonic cycles of orogenic loading-flexural subsidence/isostatic uplift-base-level falling (Catuneanu et al, 2011;Suriano et al, 2014). In addition, the available accommodation could have been modified by local factors, such as differential short wavelength uplift and subsidence of basement-cored blocks (see Dickinson, 1988;DeCelles, 2004;Marenssi et al, 2015), as well as by the integration and capture during the drainage network evolution.…”