Fluvial-derived Turbidites in the Los Molles Formation (Jurassic of the Neuquén Basin)<subtitle>Initiation, Transport, and Deposition</subtitle>

Prograding early to middle Jurassic margin, Neuquén Basin: Topset process stratigraphy and morphodynamic sediment partitioning

“…The Lajas Formation architecture in La Jardinera area is displayed well along a slightly oblique-to-dip section about 6 km long that continues into an oblique-to-strike outcrop belt of about 4 km (orange colour in Figures 5 and 6a). The work here builds on earlier research by Paim et al (2008Paim et al ( , 2011 and Olariu et al (2020).…”

“…The Cuyo Group margin, fed mainly from the North Patagonian Massif (Naipauer et al, 2017), records several sub-regional stratigraphic discontinuities (Figure 1b) likely triggered by syn depositional tectonic movements along the Huincul Arch (Leanza, 2009;Zavala, 1996a;Zavala et al, 2020;Zavala & Gonzalez, 2001). The outcrop expression of Cuyo Group clinoforms in the La Jardinera area was first mentioned by Paim et al (2008), then mapped in more detail by Olariu et al (2020) as a 'walk-out' proof that the Lajas Formation topsets are coeval with Los Molles Formation, i.e., alluvial and shallow marine topsets are physically correlated basinward with deep-water mudstones and turbidites deposited in the slope (foresets) and in the base-of-slope (bottomsets) (Giacomone et al, 2020). The long-term 'rise' in the Lajas shelf-edge trajectory (Figure 1a), itself indicating continuous, subsidence-driven aggradation, was sometimes interrupted by shorter time-scale irregularity reflecting sediment flux or sea-level changes.…”

“…The long-term 'rise' in the Lajas shelf-edge trajectory (Figure 1a), itself indicating continuous, subsidence-driven aggradation, was sometimes interrupted by shorter time-scale irregularity reflecting sediment flux or sea-level changes. These trajectory changes were accompanied by an interfingering of Los Molles and Lajas formations, with fluvial and shallowmarine conglomeratic tongues of Lajas Formation extending basinward onto the upper slope of Los Molles Formation., as documented in the outcrops of La Jardinera (Almeida Junior et al, 2020;Gan et al, 2020;Olariu et al, 2020;Paim et al, 2011). The La Jardinera outcrops are the ideal workshop locality for examining margin-scale clinoformal continuity between fluvial and shallow-marine topset deposits with deepwater slope and basin-floor fan deposits (Olariu et al, 2020).…”

“…The detail of the process stratigraphy in several areas has been differently interpreted by researchers, though the age of the deposits may also differ somewhat. Some areas have been interpretated as tide-dominated deltas, tidal flats and estuaries, because tidal signals can be discovered at most levels through Lajas Formation (McIlroy, 1999;McIlroy et al, 2005); in other areas, strong river influence is seen from the relatively coarse grain size of the sediments (Almeida Junior et al, 2020;Paim et al, 2008), and the identification of shelf-delta lobes built by sandy hyperpycnal flows (Canale et al, 2015;Steel et al, 2018). Yet other evidence of river domination on the deltas is the documentation of river-mouth bars (Kurcinka et al, 2018) and that the Lajas topsets display tidal signals mainly in the inter-flood stratigraphic intervals (Gugliotta et al, 2015).…”

“…marginal marine, shallow-marine and shelf-edge deposits (Olariu et al, 2020;Paim et al, 2008). The slope deposits of the Cuyo Group clinoforms are dominantly muddy, but with sand-filled turbidite channels (Gan et al, 2020) whereas the muddy bottomsets can have thick fan units of turbidite sandstones (slope and bottomset strata represent Los Molles Formation) (Burgess et al, 2000;Giacomone et al, 2020;Olariu et al, 2020).…”