Facies and architecture of river-dominated to tide-influenced mouth bars in the lower Lajas Formation (Jurassic), Argentina

Kurcinka, Colleen; Dalrymple, Robert W.; Gugliotta, Marcello

doi:10.1306/0609171618917155

Cited by 34 publications

(55 citation statements)

References 46 publications

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“…The deltaic nature of most of the Lajas Formation has been recognized in several studies (Spalletti, ; Zavala, ,b; McIlroy et al ., ; Kurcinka, ; Gugliotta et al ., , ,b; Rossi & Steel, ), but the dominant process controlling its deposition is still a matter of debate. For the last two decades, the Lajas Formation has been interpreted as a tide‐dominated system forming in macrotidal conditions and sharing affinities with the modern Fly River delta (McIlroy et al ., , ; Brandsaeter et al ., ; Morgans‐Bell & McIlroy, ; McIlroy, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

et al. 2016

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The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes, a tract known as the fluvial to marine transition zone, which varies between systems due to the relative strength of these processes. To understand how fluvial and tidal process interactions and the fluvial to marine transition zone are preserved in the rock record, large‐scale outcrops of deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated. Fluvial–tidal indicators consist of cyclically distributed carbonaceous drapes in unidirectional, seaward‐oriented cross‐stratifications, which are interpreted as the result of tidal modulation of the fluvial current in the inner part of the fluvial to marine transition zone. Heterolithic deposits with decimetre‐scale interbedding of coarser‐grained and finer‐grained facies with mixed fluvial and tidal affinities are interpreted to indicate fluvial discharge fluctuations (seasonality) and subordinate tidal influence. Many other potential tidal indicators are argued to be the result of fluvial–tidal interactions with overall fluvial dominance or of purely fluvial processes. No purely tidal or tide‐dominated facies were recognized in the studied deposits. Moreover, fluvial–tidal features are found mainly in deposits interpreted as interflood (forming during low river stage) in distal (delta front) or off‐axis (interdistributary) parts of the system. Along major channel axes, the interpreted fluvial to marine transition zone is mainly represented by the fluvial‐dominated section, whereas little or no tide‐dominated section is identified. The system is interpreted to have been hyposynchronous with a poorly developed turbidity maximum. These conditions and the architectural elements described, including major and minor distributary channels, terminal distributary channels, mouth bars and crevasse mouth bars, are consistent with an interpretation of a fluvial‐dominated, tide‐influenced delta system and with an estimated short backwater length and inferred microtidal conditions. The improved identification of process interactions, and their preservation in ancient fluvial to marine transition zones, is fundamental to refining interpretations of ancient deltaic successions.

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Section: Geological Backgroundmentioning

confidence: 99%

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

et al. 2016

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“…Kurcinka et al . () presents a similar interpretation in the Quebrada del Sapo locality because these authors do not recognize wave structures and associated the lower Lajas Formation with river‐dominated, tide‐influenced mouth bars. However, the back‐barrier depositional systems described here include some evidence that suggests a different scenario, including the prevalence of tidal deposits along the western to south‐western regions (Figs and ), as also indicated by McIlroy ().…”

Section: Discussionmentioning

confidence: 77%

“…(, ) these deposits represent delta systems. The Lajas Formation also encompasses facies related to tidal action, either predominant (McIlroy, ; McIlroy et al ., ; Stukins et al ., ; Rossi & Steel, ) or subordinate to fluvial facies (Gugliotta et al ., , ; Kurcinka et al ., ).…”

Section: Geological Settingmentioning

confidence: 97%

Stratigraphic evolution of the nearshore to fluvial plain of the Upper Cuyo Group, Neuquén, Argentina

et al. 2019

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The upper portion of the Cuyo Group in the Zapala region, south-eastern Neuqu en Basin (Western Argentina), encompasses marine and transitional deposits (Lajas Formation) overlain by alluvial rocks (Challac o Formation). The Challac o Formation is covered by the Mendoza Group above a secondorder sequence boundary. The present study presents the stratigraphic framework and palaeophysiographic evolution of this Bajocian to Eo-Calovian interval. The studied succession comprises the following genetic facies associations: (i) offshore and lower shoreface-offshore transition; (ii) lower shoreface; (iii) upper shoreface; iv) intertidal-subtidal; (v) supratidal-intertidal; (vi) braided fluvial to delta plain; (vii) meandering river; and (viii) braided river. The stratigraphic framework embraces four third-order depositional sequences (C1 to C4) whose boundaries are characterized by the abrupt superposition of proximal over distal facies associations. Sequences C1 to C3 comprise mostly littoral deposits and display well-defined, small-scale transgressive-regressive cycles associated with fourth-order depositional sequences. Such high-frequency cycles are usually bounded by ravinement surfaces associated with transgressive lags. At last, the depositional sequence C4 delineates an important tectonic reorganization probably associated with an uplift of the Huincul Ridge. This is suggested by an inversion of the transport trend, northwestward during the deposition of C1 to C3 depositional sequences (Lajas Formation) to a south-west trend during the deposition of the braided fluvial strata related to the C4 depositional sequence (Challac o Formation).

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“…The Lajas Formation samples were collected vertically across exposed clinothems that preserved the prograding deltaic topsets. The Lajas shelf system at Lohan Mahuida has been interpreted as a mixed‐energy deltaic system (Rossi & Steel, ), with increasing fluvial dominance landwards towards the Los Molles area to the east (Kurcinka, ). The Lajas Formation here preserves a ca.…”

Section: Stratigraphic Context and Sample Locationmentioning

confidence: 99%

New insights into the stratigraphic and structural evolution of the middle Jurassic S. Neuquén Basin from Detrital Zircon (U‐Th)/(He‐Pb) and Apatite (U‐Th)/He ages

et al. 2018

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Previous studies on the Lower‐Middle Jurassic Cuyo Group in the southern Neuquén Basin, Argentina, have discussed evidence for pre‐ and syn‐depositional structural inversion during pre‐Andean shortening. While the Cuyo Group sequence stratigraphic and facies framework are well understood, the effects of structural inversion and progressive postrift thermal subsidence on sediment provenance and dispersal, as well as the timing and magnitude of deformation during and after Cuyo Group deposition, remain poorly constrained. The Cuyo Group comprises both reservoir‐quality fluvial to deep‐marine siliciclastic deposits and a petroleum source‐rock. Thus, the temporal relationship between the onset of deformation and sediment dispersal are crucial aspects for an improved understanding of both the basin evolution and petroleum system. This study presents new detrital zircon (U‐Th)/(He‐Pb) double dating from the Los Molles and Lajas Formations of the Cuyo Group in the southern area of SW Zapala to evaluate the influence of early rift inversion on sediment routing, provenance, and palaeogeography, and to provide crucial chronostratigraphic constraints. The youngest concordant Jurassic detrital zircon (DZ) U‐Pb and He ages from the Lajas and Los Molles Formations in Lohan Mahuida and La Jardinera areas suggest a late Middle Jurassic depositional age. The DZ U‐Pb provenance analysis confirms that both formations are part of the same Middle Jurassic shelf margin and were both sourced from the Choiyoi basement, Late Triassic to Middle Jurassic Andean magmatic arc and pre‐Cuyo Group strata. The detrital He (DZHe) ages provide additional provenance constraints by recording three discrete cooling events, (1) early‐Late Triassic, (2) early‐Early Jurassic, and (3) Middle‐Late Jurassic, documenting tectonically driven exhumation during rifting and contractional stages prior to and during early Neuquén basin evolution. Triassic‐Jurassic He cooling ages of zircons derived from the Choiyoi Group document the existence of pre‐Cuyo Pangean extensional structures and basins in the source area. Furthermore, the abundance of rapidly cool DZHe ages requires rapid exhumation of both Choiyoi and Carboniferous basement. All of this evidence suggests that structural inversion in the Huincul ridge region started in the Middle Jurassic, earlier than previously proposed. Hence, this challenges conventional Cuyo Group tectono‐depositional models that advocated postrift thermal sagging as the primary control on subsidence and deposition. The occurrence of first‐cycle volcanic (U‐Th)/(He‐Pb) ages implies that the Cuyo Group burial never reached depths >4–5 kilometres. Exhumation to shallower crustal depths was spatially partitioned and driven by Cenozoic Andean shortening as constrained by AHe ages.

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Facies and architecture of river-dominated to tide-influenced mouth bars in the lower Lajas Formation (Jurassic), Argentina

Cited by 34 publications

References 46 publications

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

Recognition criteria, characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation, Argentina)

Stratigraphic evolution of the nearshore to fluvial plain of the Upper Cuyo Group, Neuquén, Argentina

New insights into the stratigraphic and structural evolution of the middle Jurassic S. Neuquén Basin from Detrital Zircon (U‐Th)/(He‐Pb) and Apatite (U‐Th)/He ages

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