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Latin American journal of sedimentology and basin analysis

versión On-line ISSN 1851-4979

Lat. Am. j. sedimentol. basin anal. vol.25 no.2 La Plata dic. 2018

 

TRABAJOS DE INVESTIGACIÓN

Depositional processes and stratigraphic evolution of the campanian deltaic system of La Anita Formation, Austral-Magallanes Basin, Patagonia, Argentina

 

Damián Moyano Paz1,2, Camila Tettamanti1, Augusto N. Varela1,3, Abril Cereceda1,4, Daniel G. Poiré1,4

1 Centro de Investigaciones Geológicas (CONICET-UNLP), Diagonal 113 #275 (B1904DPK) La Plata, Argentina. dmoyanopaz@cig.museo.unlp.edu.ar
2 Cátedra de Sedimentología, Facultad de Ciencias Naturales y Museo, UNLP, Calle 122 y 60, (1900), La Plata, Argentina.
3 Cátedra de Micromorfología de Suelos, Facultad de Ciencias Naturales y Museo, UNLP, Calle 122 y 60, (1900), La Plata, Argentina.
4 Cátedra de Rocas Sedimentarias, Facultad de Ciencias Naturales y Museo, UNLP, Calle 122 y 60, (1900), La Plata, Argentina.

Received September 21, 2018
Accepted April 5, 2019
Available online April 8, 2019


ABSTRACT

Coastal depositional systems are commonly classified in terms of the relative interaction of wave, tide and fluvial processes. The La Anita Formation represents the opportunity to study and better understand coastal sedimentary systems. It is a poorly studied prograding siliciclastic deltaic-coastal wedge accumulated in the Campanian during the foreland stage of the Austral-Magallanes Basin. A detailed depositional process-based facies analysis have allowed the definition of 13 sedimentary facies and 9 facies associations for the La Anita Formation, ranging from prodelta to interdistributary delta-channel deposits. According to the spatial distribution of these facies associations, the La Anita Formation was divided into two informal units bounded by a regional erosion surface. The lower unit shows abundant hummocky cross-bedded and bioturbated sandstones, coarsening-upward trends and mainly aggradational to progradational vertical stacking pattern, and it was interpreted as a wave-dominated fluvial-influenced delta. The upper unit is characterized by unidirectional dune cross-bedding, coarsening-upward trend and a progradational vertical stacking pattern, and was interpreted as a fluvio-dominated delta with no evidence of tide or wave influence. These two units represent two genetically unrelated depositional sequences bounded by a regional erosion surface, which is interpreted as a sequence boundary triggered by a relative sea-level fall. The lower unit is part of a progradational highstand systems tract which involves the underlying deep-marine Alta Vista Formation. The upper unit deposits reflect a complete relative sea-level cycle which includes an undifferentiated lowstand and transgressive systems tracts and, toward the top, highstand systems tract.

Keywords: Facies analysis; Deltaic systems; Wave processes; Fluvial processes; Sequence stratigraphy; Upper Cretaceous.


 

INTRODUCTION

Coastal depositional environments are extremely dynamic, showing multiple coexisting depositional systems evolving through time. The main factors controlling these systems are: i) the relative dominance of fluvial, wave and tide energies, ii) the sediment supply, iii) the basin and shoreline morphology and iv) the relative sea-level changes (Galloway, 1975; Dalrymple et al., 1992; Boyd et al., 1992; Ainsworth et al., 2011). The coastal depositional systems accumulated in the initial phase of the foreland stage of the Austral-Magallanes Basin (AMB), during the Upper Cretaceous, are poorly-studied and represent a great opportunity to continue testing hypotheses about coastal depositional systems.
The Upper Cretaceous shallow-marine and coastal depositional systems of the AMB have not received the same amount of attention as deep-marine and continental depositional systems in recent studies (Richiano et al., 2012, 2013, 2015; Varela et al., 2012a,b, 2013, 2018, Varela, 2015; Malkowski et al., 2015; Sickmann et al., 2018). The La Anita Formation (LAF) deposits have been interpreted in some regional and stratigraphic studies as accumulated in shallow-marine to coastal environments (Arbe, 1986, 2002; Manassero, 1988; Macellari et al., 1989). However, detailed sedimentological, ichnological and paleoenvironmental characterization of these deposits are needed in order to constrain depositional processes, water-salinity conditions and definition of depositional systems. The Campanian LAF deposits provide excellent exposures that allow a better understanding of coastal and shallow-marine depositional systems and to unravel the evolution of the depositional history of the AMB. The specific goals of this contribution are: i) to define the sedimentary paleoenvironments where LAF accumulated and ii) to recognize stratigraphic variations in the relative roles of depositional processes.

GEOLOGICAL SETTING

The AMB is located at the south-western part of the South American Plate, in the southern end of Argentina and Chile (Fig. 1). It presents a north-south elongated shape with a marked widening toward the south (Fig. 1). The basin is bounded by the Río Chico-Dungeness High to the east, by the Patagonian-Fueguian Andes to the west and by a transform fault to the south. The tectonic history of the AMB consist of three main tectonic stages (Biddle et al., 1986; Arbe, 1986, 2002; Robbiano et al., 1996; Kraemer et al., 2002; Peroni et al., 2002; Rodriguez and Miller, 2005; Varela et al., 2012a; Ghiglione et al., 2015; Malkowski et al., 2015; Sickmann et al., 2018): i) an initial extensional stage, related to the break-up of Gondwana during the Early to Middle Jurassic (Pankhurst et al., 2000), represented by volcanic, volcaniclastic and siliciclastic deposits of El Quemado Complex (Fig. 2; Biddle et al., 1986); ii) a thermal subsidence stage (Thitonian – Albian) associated with the transgressive deposition of the shallow- and deep-marine Springhill and Río Mayer formations, respectively (Fig. 2) (Biddle et al., 1986; Arbe, 1986, 2002; Rodriguez and Miller, 2005; Richiano et al., 2012, 2013, 2015); and finally iii) the onset of a foreland basin stage due to a compressional regime that took place in the Middle Cretaceous (ca 100 Ma) (Fig. 2; Fildani et al., 2003; Fosdick et al., 2011; Varela et al., 2012a, Ghiglione et al., 2015; Malkowski et al., 2015).


Figure 1.
Location map of the Austral-Magallanes Basin. Isopachs obtained from seismic data (Marinelli, 1998) show thickness and distribution of Cretaceous deposits. The red box shows the location of the study area.


Figure 2.
Stratigraphic scheme of the sedimentary infill for the Austral-Magallanes Basin in the Lago Argentino region (modified from Ghiglione et al., 2014; Sickmann et al., 2018).

The La Anita Formation
The La Anita Formation (Bianchi, 1967) is part of a prograding siliciclastic wedge accumulated during the foreland stage of the AMB. The age of the LAF was restricted to the Campanian based on the presence of ammonites (Riccardi and Rolleri, 1980, Riccardi, 1983; Kraemer and Riccardi, 1997)
and by recently published detrital zircon maximum depositional ages (Sickmann et al., 2018). The LAF overlies dark fine-grained deep-marine deposits of the Alta Vista Formation and it is overlaid by coarse-grained continental deposits of the Cerro Fortaleza and La Irene formations (Fig. 2). The LAF it is mainly characterized by sandstones and pebbly sandstones, with subordinate mudstones and heterolithic deposits (Feruglio, 1938, 1944, 1949; Leanza, 1972; Manassero, 1988; Macellari et al., 1989; Moyano Paz et al., 2016, 2018).

STUDY AREA AND METHODS

The study area corresponds to the Lago Argentino region, located in the southwestern part of the Santa Cruz province, Patagonia, Argentina (Figs. 1, 3). The Lago Argentino region shows complete exposures of the Mesozoic sedimentary infill of the basin. The LAF exposures are restricted to this area. Detailed sedimentary logs of the LAF exposures were measured and described for eight localities (Figs. 3, 4). Thirteen sedimentary facies (SFs) were defined based on thickness, grain-size, sorting, sedimentary structure and bioturbation index (BI; Reineck and Singh, 1980; Taylor and Goldring, 1993), which allowed the identification of depositional processes (Table 1). Nine facies associations (FAs) were identified by the recurrent appearance of groups of SFs, paleocurrent directions, stratal architecture, bounding surfaces and trace-fossil assamblages (Table 2). Paleocurrent directions were measured in dune and ripple cross-bedding structures. The lateral and vertical distribution of the FAs were constrained in order to define the depositional systems in which the LAF accumulated. Correlation of the measured sections was done by walking out or by visually tracing the first appearance of a clean coal bed using high-resolution outcrop photopanels. Also, key stratigraphic surfaces where recognized and followed in order to constrain a sequence stratigraphic framework.


Figure 3.
Geological map of the study area showing the distribution of stratigraphic units of the Austral- Magallanes Basin (modified from Kraemer and Riccardi, 1997; Ghiglione et al., 2014). Measured section names: RG = Río Guanaco; FT = Filo del Turbio; LD = Luz Divina; GF = Galpón de Freile; EA = Estancia Anita; PA = Paredón; CT = Campo Tropilla; and CC = Cerro Calafate.


Figure 4.
Detailed sedimentologic logs of the La Anita Formation at the Lago Argentino region. For location of the sections see Fig. 3.

Table 1. Characteristics of the Sedimentary Facies (SFs) identified for La Anita Formation.

Table 2. Summarized characteristics of the Facies Associations (FAs) identified for the La Anita Formation.

Pl = Planolites isp., Pa = Palaeophycus isp., Rh = Rhizocorallium isp., Ar = Arenicolites isp., Sk = Skolithos isp., Oph = Ophiomorpha isp., Dp = Diplocraterion isp., Th = Thallassinoides isp., Go = Gordia isp., Ro = Rosselia isp., Te = Teichichnus isp. and Rhiz = rhizoliths; BI: Bioturbation Index.

FACIES ASSOCIATIONS 

Facies Association 1: wave-dominated prodelta
Description: This FA transitionally overlies the deep-marine fine-grained sediments of the Alta Vista Formation and it is overlain by sandstones of the wave-dominated distal delta front sandstones (FA2). It is also recorded above the sediments of FA2 through flooding surfaces. FA1 forms tabular bodies up to 5 m thick and at least 400 m of lateral continuity. They consist of interbedded black mudstones, heterolithic deposits and very fine- to fine-grained sandstones with coarsening and thickening upward trends (Fig. 5a). Mudstones facies are typically parallel-laminated or structureless, whereas heterolithic deposits show wavy and rare flaser laminations. Sandstones facies show hummocky cross-stratification (HCS) (Fig. 5b) and parallel-lamination with sparse pebble-sized clasts. FA1 shows low abundance and low diversity of biogenic structures (BI 0 - 3) in mudstones, heterolithic and sandstones facies, but highly bioturbated sandstones (BI 4 - 5) were also observed. In the sandstone layers, the trace-fossil suite consists of burrows with coated walls attributed to Ophiomorpha isp., vertical and sub-horizontal “U”- shaped burrows with or without spreiten attributed to Diplocraterion isp., Rhizocorallium isp., and Arenicolites isp. and simple vertical and horizontal burrows attributed to Skolithos isp. The fine-grained layers show Planolites isp. as the identified traces. Vegetal remains, such as leaves, wood fragments and carbonaceous material are abundant (Fig. 5c).


Figure 5. a)
Outcrop panel of Facies Association 1 showing tabular geometry of the beds and coarsening upward trends. b) Detail of hummocky cross-stratified (HCS) sandstone facies with Ophiomorpha isp. (Oph) burrows. c) Detail bedding plane view of abundant carbonaceous remains within HCS sandstones facies.

Interpretation: FA1 reflects alternations of settling of fine-grained sediments during fair-weather conditions or in the final phase of storm events and deposition of coarser-grained sediments by combined unidirectional and oscillatory flows during storm events. The storm-generated sandstones layers show a trace-fossil suite attributed to the Skolithos ichnofacies while the fair-weather fine-grained layers show a suite related to the Cruziana ichnofacies. The general low BIs suggest a brackish to marine environment. Low BIs and the abundance of HCS beds reflect high storm events frequency with limited time available for the deposition of fair weather beds (cf. Bann et al., 2008). The presence of sparse pebble-sized clasts and abundant vegetal material reflects input from local rivers (Bhattacharya, 2006; Bann et al., 2008). The low diversity of traces within fair-weather fine-grained layers could also be reflecting fluvial influence. FA1 suggests deposition in an offshore-transition bathymetry, between the storm and the fair-weather wave base (Dott and Bourgeois, 1982; Myrow and Southard, 1996; Dumas and Arnott, 2006; Eide et al., 2015). However, due to the presence of active fluvial-current effects, FA1 is interpreted as deposited in a wave-dominated prodelta.

Facies Association 2: wave-dominated distal delta front
Description: This FA grades vertically from sediments of FA1 or from the Alta Vista Formation shales. It also overlies sediments of FA3 and FA4 through flooding surfaces. FA2 grades upward into sediments of FA3 or it is incised by channel-shaped bodies of FA4 and FA5. It forms low-angle clinothems (4° - 7°) composed of very fine- to fine-grained sandstones with coarsening-upward trends (Fig. 6a) up to ~15 m thick. In some cases, they amalgamate and generate composite units up to 45 m thick and few hundred meters of lateral continuity. FA2 shows interbedded highly bioturbated (BI 4 - 6) and HCS and parallel-laminated sandstones facies (Fig. 6a-b) with lower BI (BI 1 – 3). Stratified sandstones facies are frequently present as strongly amalgamated sandbodies up to 10 m thick and more than 100 m of lateral continuity with internal erosional surfaces (Fig. 6a), mudstone rip-up clasts and soft-sediment deformation structures facies. The trace-fossil suite is composed mainly of burrows with coated walls attributed to Ophiomorpha isp. (Fig. 6c) and horizontal spreiten “U”-shaped burrows attributed to Rhizocorallium isp., although Thallassinoides isp. galleries, vertical spreiten “U”-shaped burrows attributed to Diplocraterion isp., and simple vertical and horizontal burrows attributed to Skolithos isp., Planolites isp. and Palaeophycus isp. are also present.


Figure 6.
Representative outcrop photographs of Facies Association 2. a) Coarsening-upward trend showing interbedding of hummocky cross-stratified (HCS) beds and highly bioturbated sandstones, and amalgamated HCS on top (view to the southeast). b) Detail of bioturbated and HCS sandstone deposits. c) Detail of abundant Ophiomorpha isp. burrows in bioturbated sandstone facies.

Vegetal remains, such as leaves, wood fragments and carbonaceous material are abundant.
Interpretation: HCS and parallel-laminated sandstones reflect friction-dominated, combined- and oscillatory-flow generated structures formed during storm events (Myrow and Southard, 1996; Dumas and Arnott, 2006), whereas bioturbated beds are the result of the reworking of those storm-sheets by organisms during fair-weather conditions (Bann et al., 2008; Buatois and Mángano, 2011). Strongly amalgamated storm-generated sandbodies indicate high frequency of relax-currents generated after storm events (post-storm flows) that eroded bedforms generated under fair-weather conditions (Dott and Bourgeos, 1982; Isla et al., 2018). The trace-fossil suite is attributed to a stressed expression of proximal Cruziana to distal Skolithos (MacEachern et al., 2007; Bann et al., 2008; Buatois and Mángano, 2011), developed in a brackish to marine environment with high recurrence of storm events. The presence of sparse pebble-size clasts and vegetal remains reflect input from local rivers (Bhattacharya, 2006; Bann et al., 2008). FA2 suggests deposition in a zone above the fair-weather wave base (Clifton, 2006), however, the presence of fluvial-currents effect suggest deposition in a wave-dominated distal delta front environment.

Facies Association 3: wave-dominated proximal delta front
Description: FA3 forms tabular, horizontal to gently inclined (3° - 5°) bodies that grades vertically from the sediments of the wave-dominated distal delta front (FA2) into gray-colored, well-sorted, fine- to medium-grained sandstones (Fig. 7). It is overlaid by channelized incisions of FA4 or by FA2 deposits. FA3 is up to 5 m thick and tens of meters lateral continuity. It is composed of trough cross-bedding sets up to 0.4 m thick (Fig. 7). Parallel-laminated and asymmetric ripple cross-laminated facies with sparse pebble-sized clasts are common. The cross-beds are oriented toward the northeast (Table 2). This FA is typically unburrowed (BI 0 - 2), however, a scattered trace-fossil suite composed of vertical burrows attributed to Ophiomorpha isp. and Skolithos isp. is present near the top of the layers. Vegetal remains, such as leaves are present.


Figure 7.
Tabular beds of Facies Association 3 showing abundant unidirectional trough cross-bedded clean sandstones.

Interpretation: FA3 reflects deposition by tractive unidirectional currents. The low abundance and low diversity of trace-fossil is attributed to a stressed expression of the Skolithos ichnofacies, indicating high-energy conditions in a brackish-water environment (Bann et al., 2008; Buatois and Mangano, 2011; MacEachern et al., 2005, 2007, 2010, 2012). The presence of vegetal remains and pebble-sized clasts reflect input from local rivers (Bhattacharya, 2006; Bann et al., 2008). FA3 is interpreted as mouth bar deposits (Enge et al., 2010) developed in a wave-dominated proximal delta front environment. Although no wave-generated structures were recorded in this FA, the effects of wave-processes are inferred because of the absence of a silty matrix within the sand which is associated with high frequency oscillatory motion of waves (Plint, 2010; Ainsworth et al., 2016) and because FA3 shows vertical association with the wave-dominated deposits of FA2.

Facies Association 4: single-story distributary channels
Description: This FA erosionally overlies sediments of the wave-dominated distal delta front (FA2) or the wave-dominated proximal delta front (FA3) and it is overlain by FA2 deposits through flooding surfaces. FA4 consists of non-amalgamated lenticular sandbodies up to 6 m thick and 20 m wide (maximum) with erosional, concave-up base (Fig. 8a). These are composed of poorly-sorted, medium-to coarse-grained sandstones and pebbly-sandstones with fining-upward trends (Fig. 8b). FA4 shows abundant well-marked dune cross-bedded facies (Fig. 8c). Toward the top of these bodies, parallel-laminated and asymmetric ripple cross-laminated sandstones are common, and toward the base it shows a lag with mudstones rip-up and pebble-sized clasts (Fig. 8b, d). The paleocurrent directions measured on cross-beds are dominantly toward the southeast (Table 2). Although this FA is typically unburrowed (BI 0 - 1), it shows a scattered trace-fossil suite with Ophiomorpha isp., Diplocraterion isp., Skolithos isp. and lower proportions of Palaeophycus isp. and Gordia isp. Vegetal remains, such as leaves, wood fragments and carbonaceous material are abundant.


Figure 8.
Representative outcrop photographs of Facies Association 4. a) Non-amalgamated channel-shaped body with concave-up, erosional base. b) Detail of the fining upward channel deposit with coarse-grained lag toward the base and parallel-laminated coarse-grained sandstones toward the top. c) Detail of trough and tangential cross-bedded sandstones facies. d) Coarse-grained mudstone rip-up clasts.

Interpretation: FA4 reflects deposition by tractive unidirectional currents. The erosional nature of the base, the fining-upward grain size trend, the presence of poorly sorted sediments, the unidirectional cross-beds, the lag at the base of some bodies and the abundant vegetal remains within these deposits indicate that FA4 was deposited in single-story fluvial distributary channels. The presence of a trace-fossil suite, attributed to a stressed expression of Skolithos ichnofacies (Beynon and Pemberton, 1992; Gibert and Martinell, 1993; MacEachern and Gingras, 2007; Bann et al., 2008; Buatois and Mángano, 2011; MacEachern et al., 2005, 2007, 2010, 2012) in some of these channels, indicates brackish-water conditions, suggesting marine influence in the most distal part of the channels (Bhattacharya, 2006; Fielding, 2010).

Facies Association 5: terminal distributary channels
Description: This FA is composed of amalgamated
pebbly-sandstone bodies up to 7 m thick. They incise into sediments of wave-dominated distal delta front (FA2) and are overlain by single-story distributary channels (FA4). Individual bodies, or stories, are 1.5 m thick and few meters wide each and are composed of poorly-sorted pebbly-sandstones and fine-grained sandstones with fining-upward trends (Fig. 9). The erosional bases of the stories show coarse-grained lags followed by 3D cross-bedding facies that in turn grade upward to bioturbated sandstones (BI 1 - 6; Fig. 9). The paleocurrent directions determined from cross-beds are dominantly toward the southeast (Table 2). The trace-fossil suite consists of a monospecific assemblage of burrows with coated walls attributed to Ophiomorpha isp. with scattered simple vertical and horizontal burrows attributed to Skolithos isp. and Palaeophycus isp. Vegetal remains, such as leaves fragments and carbonaceous material are abundant.


Figure 9.
Detail of Facies Association 5 showing amalgamated, erosionally based bodies, with fining-upward trend. The trough cross-beds at the base of these stories are obscured upward due to the gradual increase in the bioturbation index (BI 1 - 6).

Interpretation: FA5 reflects deposition by tractive unidirectional currents. The monospecific trace-fossil suite is attributed to a stressed expression of the Skolithos ichnofacies developed in a brackish to marine environment (Beynon and Pemberton, 1992; Gibert and Martinell, 1993; MacEachern and Gingras, 2007; Bann et al., 2008; Buatois and Mángano, 2011; MacEachern et al., 2005, 2007, 2010, 2012). The erosional nature of the base of these bodies, the presence of dune cross-bedded facies, the poorly-sorted character, the fining-upward grain-size trends, the upward increase of BI and the abundant vegetal fragments within this FA indicates deposition in terminal distributary channels (Olariu and Bhattacharya, 2006). The presence of distal delta front (FA2) and distributary channels (FA4) deposits below and above, respectively, supports the terminal distributary channel interpretation.

Facies Association 6: fluvio-dominated distal delta front
Description: This FA forms gently inclined (6° - 8°) tabular sandbodies (Fig. 10a) that dip toward the southeast and grade upward to coarser-grained sediments of fluvio-dominated mouth bars deposits (FA7; Fig. 10b). FA6 is composed of very fine- to fine-grained, poorly-sorted sandstones with abundant silty matrix. Primary sedimentary structures are obscured because of high bioturbation intensity (BI 4 - 5), however, parallel-laminated and small-scale trough cross-bedded and asymmetric ripple-laminated sandstones are observed. This FA shows low diversity but high abundance of biogenic structures. The trace-fossil suite is composed of burrows with coated walls attributed to Ophiomorpha isp., vertically stacked horizontal burrows attributed to Teichichnus isp., and simple horizontal burrows attributed to Planolites isp. and Palaeophycus isp. Vegetal remains, such as leaves, wood fragments and carbonaceous material are abundant.


Figure 10.
Representative outcrop photographs of Facies Association 6. a) Detail of the gently inclined bioturbated tabular sandbodies. b) Detail showing the poorly-sorted, highly bioturbated sandstones (BI 4-5), with local parallel-lamination that coarsens upward into sandstones of Facies Association 7.

Interpretation: The low diversity, but still high abundance of trace-fossils suggests accumulation in a low-energy and low-stress, brackish to marine environment associated with Cruziana ichnofacies. The presence of small-scale cross-bedding and parallel-lamination indicates deposition by unidirectional currents. The presence of abundant silty matrix and widespread vegetal remains suggest that these currents were fluvio-derived. Because of these features, FA6 is interpreted as the episodic deposition of turbidity currents in a fluvio-dominated distal delta front environment (Bhattacharya, 2006; Enge et al., 2010; Li et al., 2011; Kurcinka et al., 2018) that grades upward into fluvio-dominated mouth bars (FA7).

Facies Association 7: fluvio-dominated proximal delta front
Description: This FA commonly grades vertically from the sediments of the fluvio-dominated distal delta front (FA6) into poorly-sorted coarser-grained sandstones and pebbly sandstones (Figs. 10b). It is overlain by channelized incisions of high-sinuosity distributary channels (FA8) or by deposits of the interdistributary areas (FA9). FA7 consists of amalgamated high-angle (8° - 15°) sandy-clinothems up to 30 m thick and a few hundred meters wide that dips toward the southeast (Fig. 11a-c). Each clinothem is 5 – 7 m thick and composed of yellow-colored, medium- to coarse-grained sandstones and pebbly-sandstones with abundant silty matrix, showing both coarsening and fining upward trends. They show well-marked meter-scale cross-bedding structures (Fig. 11c-d) and subordinated parallel-laminated and ripple cross-laminated deposits. The paleocurrent directions measured from the cross-beds are mainly toward the southeast (Table 2). The lower portion of these bodies shows mudstones rip-up clasts and vegetal remains, such as leaves, wood fragments and carbonaceous material. Drapes of terrestrial phytodetritus are common in the cross-beds foresets. These drapes do not show a cyclic spacing distribution. This FA is typically unburrowed, however, sparse vertical burrows (BI 0 - 2) attributed to Ophiomorpha isp., Skolithos isp., Arenicolites isp. and Rosselia isp. appear mainly on top of some bodies.


Figure 11.
Representative outcrop photographs of Facies Association 7. a) and b) Outcrop panels showing high-angle forward-accretion clinothems dipping toward the southeast. c) Detail of the forward-accretion climothems. The inset in Fig. 11c shows detail of internal dune cross-bedding dipping in the same direction as the clinothems. d) Detail of internal large-scale dune cross-bedding.

Interpretation: FA7 reflects deposition by tractive unidirectional currents. Because of the high-angle clinothem geometry with forward-accretion of these beds (Fig. 11a-c), the unidirectional current-generated structures, the poor sorting, and the low BI, this FA is interpreted as mouth bar deposits, accumulated in a fluvio-dominated proximal delta front environment (Olariu et al., 2010; Enge et al., 2010; Kurcinka et al., 2018). This is also supported by the vertical association with the distal delta front and distributary channels, as well as the presence of a trace-fossil suite attributed a stressed expression of the Skolithos ichnofacies developed in a high-energy, brackish-water environment (Beynon and Pemberton, 1992; Gibert and Martinell, 1993; MacEachern and Gingras, 2007; Bann et al., 2008; Buatois and Mángano, 2011; MacEachern et al., 2005, 2007, 2010, 2012).

Facies Association 8: multi-story distributary channels
Description: This FA consists of amalgamated lenticular bodies 5 – 30 m thick with erosional, concave up base (Fig. 12a-b) that incises into the mouth bars of the fluvio-dominated proximal delta front (FA7). It also cuts down into sediments of FA2 and FA5 through a regional erosional surface. It occurs in vertical association with fine-grained interdistributary area deposits (FA9). Individual stories are up to 10 m thick and are separated by erosion surfaces, showing internal 2 m high and up to 30 m long inclined (20° - 35°) lateral accretion surfaces (Fig. 12b) that dip toward the northeast and southwest. These stories are filled with poorly-sorted coarse-grained sandstones and pebbly-sandstones. They show 3D dune cross-bedded facies and fining-upward trends (Fig. 12c-d). Soft-sediment deformation structures, parallel-laminated and ripple cross-laminated sandstones, as well as structureless conglomerates deposits are also present. Erosional bases of stories are covered by a lag with pebble-sized clasts and mudstone rip-up clasts together with abundant vegetal remains, such as leaves and wood fragments. Organic phytodetritus drapes are present in the foreset and toeset of cross-beds showing noncyclical spacing on their distribution (Fig. 12d). Cross-beds are oriented mainly toward the southeast (Table 2). This FA is typically unburrowed, however, a sparse trace-fossil suite (BI 0 - 1) composed of vertical Ophiomorpha isp., Skolithos isp. and Arenicolites isp. burrows is present.


Figure 12.
Representative outcrop photographs of Facies Association 8. a) Detail of channel-shaped body with concave-up, erosional base. b) Photopanel showing lenticular amalgamated stories with internal lateral accretion surfaces and bounded by high hierarchy erosional surfaces. c) Details of fining upward trends and trough cross-bedded facies. d) Organic matter drapes on cross-beds toesets with noncyclical spacing.

Interpretation: This FA reflects deposition by high-energy tractive unidirectional currents. The internal lateral accretion surfaces indicate high-sinuosity of these currents. Based on the erosional nature of the bodies base, the poor sorting of their infill, the fining upward grain size trend, the current-generated structures, the lag at the base of some bodies and the abundant vegetal remains evidences, this FA is interpreted as high-sinuosity meandering distributary channels within a delta plain environment (Bhattacharya, 2006; Olariu and Bhattacharya, 2006). The presence of a marine trace-fossil suite attributed to a stressed expression of Skolithos ichnofacies (Beynon and Pemberton, 1992; Gibert and Martinell, 1993; MacEachern and Gingras, 2007; Bhattacharya, 2006; Buatois and Mangano, 2011; MacEachern et al., 2005, 2007, 2010, 2012) in some channels indicates brackish-water conditions (Bhattacharya, 2006; Fielding, 2010). The lateral and vertical complexity of channel bodies indicate that their infill was multi-story. The close association with the interdistributary areas deposits (FA9) supports this interpretation.

Facies Association 9: interdistributary areas
Description: This FA is in vertical association with multi-story distributary channels of FA8 and consists of tabular bodies with thicknesses that range from 1 to 17 meters. It is composed of organic-rich black mudstones to clean coal, siltstones and subordinate very fine-grained sandstones (Fig. 13a). They show parallel-laminated or structureless mudstones deposits with pedogenic features such
as slickensides, both angular and subangular blocky peds, and abundant rhizoliths. The BI is low (0 – 1) with horizontal simple burrows attributed to Planolites isp. as the dominant trace, but sandstone layers are occasionally intensely bioturbated (BI 4 – 5) with horizontal burrows of Planolites isp. and Teichichnus isp. as the identified traces. In addition to carbonaceous material, wood fragments are common. These fine-grained layers are eventually interrupted by lenticular bodies of fine-grained sandstones with sharp bases and convex-up tops (Fig. 13b) with trough cross-bedded and parallel-laminated facies and sparse vertical burrows attributed to Ophiomorpha isp.


Figure 13.
Representative outcrop photographs of Facies Association 9, a) Panel showing tabular clean coal to organic-rich mudstones deposits. b) Detail of trough cross-bedded convex-up lenticular body interpreted as crevasse splay deposits, interbedded with organic-rich mudstones.

Interpretation: Fine-grained deposits suggest low-energy conditions during the accumulation of the FA9. It is interpreted to have been deposited in waterlogged, swamp-like interdistributary areas filled by overbank spilling of fine-grained material from distributary fluvial channels (AF8) during flood stages (Bhattacharya, 2006; Fielding, 2010). The lobular sandbodies with tractive structures reflect deposition by unidirectional tractive currents and are interpreted as crevasse-splays deposits (Mjøs et al., 1993; Perez-Arlucea and Smith, 1999). The pedogenic features and the presence of abundant poorly-decomposed organic matter suggest soil development in a waterlogged environment with reductive conditions (Everett, 1983; Retallack, 2001). The presence of marine traces indicates that brackish-water conditions were established occasionally in these interdistributary areas (Gugliotta et al., 2015).

DISCUSSION

Stratigraphic architecture and distribution of facies associations
The LAF deposits can be differentiated into two units, here defined as upper unit and lower unit. This differentiation is based on their color difference and the presence of a regional low-angle erosion surface bounding them that incise ~ 50 m into the underlying lower unit (Figs. 4, 14). In addition, this stratigraphic differentiation coincides with the vertical variations in the relative roles of depositional processes and spatial distribution of FAs (Figs. 4, 15) which are further discussed below.


Figure 14.
Outcrop photograph of the cliff at the Anita farm with a view to the south, showing the stratigraphic distribution of the Upper Cretaceous – Paleocene deposits of the AMB. The LAF lower unit shows gray-colored strata and low-angle clinoforms dipping toward the southeast. The upper unit of the LAF shows yellow-colored strata. The upper and lower units of the LAF are bounded by a regional erosional surface.


Figure 15.
Correlation panel showing vertical stacking patterns and lateral distribution of Facies Associations (FAs) together with the sequence stratigraphic framework for the La Anita Formation. The maximum flooding surface (MFS) and the first clean coal bed had been walked and used as correlation datum. AVF = Alta Vista Formation; CCF = Cerro Fortaleza Formation; LIF = La Irene Formation.

The FAs of the LAF evidence both marine and fluvial processes being active in different proportions during its accumulation. In this contribution we followed the ideas proposed by Ainsworth et al. (2008) who set up criteria for defining process dominance and influence within facies associations in mixed-process coastal systems. The most common sedimentary structures define the dominant depositional process within a FA, and secondary processes which lead to the generation of subordinate features are said to have influenced deposition. The dominant and subordinate processes that constitute the largest proportion of a stratigraphic unit are considered to represent the dominant and subordinate processes that were active in the stratigraphic unit (cf. Ainsworth et al., 2008, 2011).

Lower unit
This unit coarsens upward and grades from fine-grained slope deposits of the Alta Vista Formation (Malkowski et al., 2017) into a dominantly sandy, gray-colored succession. Its upper boundary is a regional erosion surface which in turn is followed by the upper unit deposits of the LAF (Figs. 4, 14, 15). The vertical stacking pattern of the FAs of the lower unit is mainly aggradational to progradational, although the coarsening-upward grain size trends suggests a progradational depositional system (Figs. 4, 15).
The abundance of HCS and other wave-generated structures, such as parallel-lamination and wavy-lamination all along prodelta and distal delta front deposits of FA1 and FA2, respectively, suggests deposition under strong influence of fair weather wave- and storm-processes. However, fluvial-current effects are also recognized in these FAs in the form of pebble-sized clasts and abundant land-driven vegetal remains. The trace-fossil suites indicate high-energy conditions associated with the high recurrence of storm events. In parallel, the low abundance and diversity of traces, especially those found on fair-weather beds of FA1, could also be responding to stressing conditions produced by low salinity and bottom oxygenation, associated with fluvial-discharge effects in the coastal area.
Mouth bar deposits of FA3 are poorly represented in the lower unit. They grade from wave- and storm-generated layers of FA2 into well-sorted sandstones, and are overlain by channel incisions (FA4) or by wave-dominated distal delta front deposits (FA2). Mouth bar deposits develop when a turbulent current expands from the mouth of a distributary channel into a standing body of water (Wright, 1977). Mouth bars are, by definition, generated by fluvial processes. However, the recognition of a wave-dominated distal delta front under and above these mouth bar deposits, together with the lack of a silty matrix, suggest that they were developed in a wave-dominated context. The scarce proportion of mouth bar deposits in the lower unit (Fig. 15) could be related to the high recurrence of storm events, evidenced in the prodelta and distal delta front deposits, because during storms, high amounts of sand are stripped from shallow-water zones and transported seaward (Dumas and Arnott, 2006).
Cross-bedded structures from distributary and terminal distributary channel deposits of FAs 4 and 5 show mean paleocurrent directions toward the southeast (Fig. 15; Table 2), however, terminal distributary channels cross-beds orientation show greater dispersion in the measured data than the channels of FA4 were the dispersion is considerably minor (Table 2). Cross-beds orientation from mouth bars (FA3) are oblique, almost orthogonal, to both distributary and terminal distributary channels mean paleoflow (Fig. 15; Table 2). This oblique flow relationship suggests an oblique wave-approaching to the shoreline and this may again reflects wave influence on mouth bars (Ainsworth et al., 2016).
The progradational depositional system of the lower unit of the LAF is interpreted as wave-dominated, fluvial-influenced delta system (cf. Ainsworth et al., 2008, 2011; Fig. 16a). Even though the delta was fed by distributary fluvial channels, the distribution of the sediment was dominated by the action of waves. Storm and wave effects
are strongly represented in the sediments of the prodelta (FA1) distal delta front (FA2) and mouth bars (FA3; Figs. 4, 15; Table 2). Although fluvial-currents do not appear as a dominating process during the deposition of the lower unit, it is present in all FAs as subordinate features (Figs. 4, 15). These fluvial-influenced features within the lower unit deposits are a key element to differentiate between wave-dominated deltas and nonfluvialite wave-dominated shoreface-shelf depositional systems (sensu Ainsworth et al., 2011). The oblique wave-approaching to the coastline produces mouth bars deflection and migration in a shore-parallel direction for several kilometers (Bhattacharya et al., 2010), passing gradationally into attached beach ridge and/ or coexisting shoreface deposits (Rodriguez et al., 2000; Bhattacharya and Giosan, 2003; Sømme et al., 2008; Bhattacharya, 2010; Ainsworth et al., 2019; Fig. 16a). Paleocurrent directions of the lower unit indicate that progradation of the system was toward the southeast (Table 2; Figs. 15, 16a). This is further supported by the presence of clinoform dipping surfaces toward the same direction (Fig. 14).


Figure 16.
Paleoenvironmental and paleogeographic reconstruction for the La Anita Formation deposits. a) Lower unit and b) upper unit. Rose-diagrams show paleocurrent directions of each Facies Association (FA).

Upper unit
The base of this unit coincides with the regional erosion surface dividing the two units defined in this work (Figs. 4, 14, 15). The upper unit shows no lateral nor vertical gradations with the underlying lower unit and it is overlain by the Upper Cretaceous Continental Deposits (sensu Tettamanti et al., this volume) of the La Irene or Cerro Fortaleza formations, representing a progressive continentalization of the basin. The upper unit is yellow-colored and shows coarser grain size than the lower unit (Figs. 4, 14). The vertical stacking pattern of FAs suggests deposition by a progradational depositional system (Fig. 15).
Multi-story distributary channels (FA8) are found in the lower portion of the unit, above the regional erosional surface, as well as in the upper portion of this unit, in this case associated with fine-grained deposits of the interdistributary areas (FA9; Fig. 15). Deposition within these channels do not record any influence of marine-processes (i.e. waves nor tides).
Distal delta front and mouth bar sediments of the upper unit of the LAF differ considerably from those present in the lower unit. The distal delta front (FA6) is associated with a low-energy brackish-water environment. The presence of silty matrix and parallel-laminated, asymmetric-ripples and cross-bedded facies suggest deposition by unidirectional fluvial-currents with no evidence of wave or tidal influence. FA6 grades vertically and laterally into coarser-grained mouth bar deposits (FA7). These
mouth bar deposits differ from the lower unit ones because they are clearly poorly-sorted, with abundant silty matrix; are coarser-grained and form amalgamated high-angle dipping clinothems. No wave, or tidal effects were recorded in mouth bars of FA7 suggesting that deposition was dominated by fluvial-processes.
The upper unit of the LAF evidence deposition dominated by fluvial processes in a stressed brackish-water environment. This progradational, coarsening-upward system is interpreted as a fluvio-dominated delta (Ainsworth et al., 2008; 2011; Fig. 16b). Mouth bars and distributary channels show a wide range of paleocurrent directions (Figs. 15, 16b; Table 2), as expected in a fluvio-dominated delta. However, the progradation of the system was, as in the lower section, toward the southeast (Fig. 16b).

Sequence stratigraphic implications
The two units of the LAF could be attributed as part of the same depositional sequence, where both would represent coexisting lateral active lobes of an asymmetrical-delta (Bhattacharya and Giosan, 2003). Alternatively, they can be considered as two different depositional sequences. In the first case both units should be genetically related, representing temporal variations in shoreline trajectory and paleogeography, and they should show oblique direction of progradation as suggested by Charvin et al. (2010). However, our data suggest that both units of the LAF are genetically unrelated because: i) no
lateral relationship in FAs distribution was recorded between them, ii) both show the same southeastward direction of progradation that suggests the same direction in shoreline trajectory, and iii) they present a regional erosion surface bounding them.
This erosion surface consists of a low-relief regional incision that cuts down ~ 100 m into the underlying wave-dominated fluvial-influenced delta system of the lower unit (Figs. 14-16). This surface is immediately overlain by the coarsest grained, laterally and vertically amalgamated multi-story channel deposits (FA8) of the upper unit. The multi-story, multi-lateral nature of these channels could represent the fill of coastal incised valleys (Fielding, 2010), associated to a sequence boundary triggered by a relative sea-level fall (Catuneanu, 2006; Catuneanu et al., 2009; Figs. 15, 16).
In turn, the lower unit of the LAF grades from the deep-marine, slope black shale deposits of the Alta Vista Formation (Malkowski et al., 2017). The lower unit is interpreted as the highstand systems tract (HST), indicated by the aggradational to progradational vertical stacking pattern of its FAs and by its location immediately below the interpreted sequence boundary (Catuneanu, 2006; Catuneanu et al., 2009; Fig. 15). The upper unit of the LAF shows evidence a complete relative sea-level cycle. The lowest interval of the upper unit is represented by incised valley fill deposits and it is interpreted as an undifferentiated lowstand and transgressive systems tracts (LST-TST; Fig. 15). It is not possible to distinguish between the LST and the TST because of the lack of lateral gradation to distal deposits (Catuneanu, 2006; Kurcinka et al., 2018). The top of the LST-TST is marked at the base of the fluvio-dominated delta front (FAs 6 and 7), interpreted as the maximum flooding surface (MFS; Catuneanu, 2006; Catuneanu et al., 2009; Fig. 15). The expression
of the MFS is progressively lost toward the north of the study area (Fig. 15). The deposits above the LST-TST are represented by the fluvio-dominated delta front (FAs 6 and 7) and delta plain (FAs 8 and 9) deposits, with a strongly progradational stacking pattern. For this reason, the latter are interpreted as the HST (Catuneanu, 2006, Catuneanu et al., 2009; Kurcinka et al., 2018; Fig 15).

CONCLUSIONS

This study highlights the importance of depositional process-based facies analysis for interpreting coastal depositional systems in order to determinate the role of wave, tidal and/or fluvial processes during deposition. The La Anita Formation is interpreted as a deltaic depositional system, which shows vertical variations in the relative roles of wave and fluvial processes. This allowed to differentiate the La Anita Formation deposits into a wave-dominated lower unit and a fluvio-dominated upper unit, each representing different depositional sequences.
The lower unit of the La Anita Formation is interpreted as a wave-dominated fluvial-influenced delta system, based on the presence of wave-generated structures, coarsening-upward trends and aggradational to progradational vertical stacking patters. Wave-processes controlled the deposition on the prodelta and the distal delta front. Also the oblique wave-approach to the coastline elongated mouth bars deposits in a shore-parallel direction. This wave-dominated, fluvial-influenced delta is interpreted as part of a HST located under the interpreted sequence boundary.
The upper unit and the lower unit are bounded by a regional erosion surface which is interpreted as a sequence boundary related to a relative sea-level fall. This explains why there is no evidence of vertical nor lateral gradation between the lower and the upper units.
The upper unit of the La Anita Formation has been interpreted as a fluvio-dominated delta system, with abundant unidirectional current-generated structures, coarsening-upward trend, and overall progradational vertical stacking pattern of its facies associations. This unit does not record any wave nor tidal effects and its deposits reflect a complete relative sea-level cycle. The lowermost channelized deposits represent incised valley fills related with the sequence boundary and are interpreted as the undifferentiated LST-TST which is covered by the HST through the maximum flooding surface.

Acknowledgments

This research was founded by National Research Council (CONICET) PIP-0866 granted to Dr. D.G. Poiré. The authors would like to thank Dafne Fraser, Facundo Echeverria and Adrian Prieto of the Anita farm and to Firmo Vigil, Raúl Cherbukov and family of the Irene farm for their hospitality, kindness and facilities to carry out fieldwork. Invited Editor Jose I. Cuitiño, and the reviewers Marcello Gugliotta and anonymous reviewer are acknowledged for their thorough and constructive comments which have significant improved the manuscript. The authors also thank Cecilia M. Moyano Paz for her contribution with the language improvement.  

REFERENCES 

1. Ainsworth, R.B., S.S. Flint and J.A. Howell, 2008. Predicting coastal depositional style: Influence of basin morphology and accommodation to sediment supply ratio within a sequence stratigraphic framework. In: G.J. Hampson, R.J. Steel, P.B. Burgess and R.W. Dalrymple (Eds.), Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy. Society for Sedimentary Geology, Special Publication, 90:237-263.         [ Links ]

2. Ainsworth, R.B., B.K. Vakarelov and R.A. Nanson, 2011. Dynamic spatial and temporal prediction of changes in depositional processes on clastic shorelines: Toward improved subsurface uncertainty reduction and management. AAPG Bulletin 95:267-297.         [ Links ]

3. Ainsworth, R.B., B.K. Vakarelov, J.A. MacEachern, R.A. Nanson, T.I. Lane, F. Rarity and S.E. Dashtgard, 2016. Process-driven architecture variability in mouth-bar deposits: a case study from a mixed-process mouth-bar complex, Drumheller, Alberta, Canada. Journal of Sedimentary Research 86, 512- 541.         [ Links ]

4. Ainsworth, B.R., B.K. Vakarelov, C.H. Eide, J.A. Howell and J. Bourget, 2019. Linking the high-resolution architecture of modern and ancient wave-dominated deltas: Processes, products, and forcing factors. Journal of Sedimentary Research 89:168-185.         [ Links ]

5. Arbe, H.A., 1986. Estratigrafía, discontinuidades y evolución sedimentaria del Cretácico en la Cuenca Austral, Prov. De Santa Cruz. In: G. Chebli and L.A. Spalletti (Eds.) Cuencas Sedimentarias Argentinas. Instituto Superior de Correlación Geológica, Universidad Nacional de Tucumán, Serie de Correlación Geológica 6:419-442.         [ Links ]

6. Arbe, H.A., 2002. Análisis estratigráfico del Cretácico de la Cuenca Austral. In: M.J. Heller (Ed.), Geología y Recursos Naturales de Santa Cruz. XV Congreso Geológico Argentino 103-128.         [ Links ]

7. Bann, K.L., S.T. Tye, J.A. MacEachern, C.R. Fielding and B.G. Jones, 2008. Ichnological and sedimentologic signatures of mixed wave- and storm-dominated deltaic deposits: examples from the early Permian Sydney Basin, Australia. In: G.J. Hampson, R.J. Steel, P.B. Burgess and R.W. Dalrymple (Eds.), Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy. Society for Sedimentary Geology, Special Publication, 90:293-332.         [ Links ]

8. Beynon, B.M., and S.G. Pemberton, 1992. Ichnological signature of brackish water deposit, an example from the Lower Cretaceous Grand Rapids Formation, Cold Lake oil sands area, Alberta. In S.G. Pemberton (Ed.), Applications of Ichnology to Petroleum Exploration: A Core Workshop. Society for Sedimentary Geologists, 17:199-221.         [ Links ]

9. Bhattacharya, J.P., and L. Giosan, 2003. Wave-influenced deltas: geomorphological implications for facies reconstruction. Sedimentology, 50:187-210.         [ Links ]

10. Bhattacharya, J.P., 2006. Deltas. In: H.W. Posamentier and R.G. Walker (Eds.), Facies Models, Society for Sedimentary Geology, Special Publication, 84:237-292.         [ Links ]

11. Bhattacharya, J.P., 2010. Deltas. In: R.G. Dalrymple and N.P. James (Eds), Facies Models, Fourth Edition, 233-262.         [ Links ]

12. Biddle, K., M. Uliana, R. Jr. Mitchum, M. Fitzgerald and R. Wright, 1986. The stratigraphic and structural evolution of central and eastern Magallanes Basin, Southern America. In: P. Allen and P. Homewoods (Eds.), Foreland basins. International Association of Sedimentologists, Special Publication 8:41-61.         [ Links ]

13. Boyd, R., R. Dalrymple and B.A. Zaitlin, 1992. Clasification of clastic coastal depositional environments. Sedimentary Geology, 80:139-150.         [ Links ]

14. Buatois, L.A. and M.G. Mángano, 2011. Ichnology: Organism- Substrate Interactions in Space and Time. Cambridge University Press, 358 pp.         [ Links ]

15. Catuneanu, O, 2006. Principles of sequence stratigraphy, Amsterdam, Elsevier 386 pp.         [ Links ]

16. Catuneanu, O., V. Abreu, J.P. Bhattacharya, M.D. Blum, R.W. Dalrymple, P.G. Eriksson, C.R. Fielding, W.L. Fisher, W.E. Galloway, M.R. Gigbling, K.A. Giles, J.M. Holbrook, R. Jordan, C.G.St.C. Kendall, B. Marcuda, O.J. Martinsen, A.D. Miall, J.E. Neal, D. Nummedal, L. Pomar, H.W. Posamentier, B.R. Pratt, J.F. Sarg, K.W. Shanley, R.J. Steel, A. Strasser, M.E. Tucker and C. Winker, 2009. Towards the standardization of sequence stratigraphy. Earth-Science Reviews, 92:1-33.         [ Links ]

17. Charvin, K., G.J. Hampson, K.L. Gallagher and R. Labourdette, 2010. Intra-parasequence architecture of an interpreted asymmetrical wave-dominated delta. Sedimentology, 57:760-785.         [ Links ]

18. Clifton, H.E., 2006. A reexamination of facies models for clastic shorelines. In: H.W. Posamentier and R.G. Walker (Eds.), Facies Models, Society for Sedimentary Geology, Special Publication, 84:293-337.         [ Links ]

19. Dalrymple, R.W., B.A. Zaitlin and R. Boyd, 1992. Estuarine facies models: conceptual basis and stratigraphic implications. Journal of Sedimentary Petrology, 62:147-173.         [ Links ]

20. Dumas, S. and R.W.C. Arnott, 2006. Origin of hummocky and swaley cross-stratification- The controlling influence of unidirectional current strength and aggradation rate. Geology, 34:1073-1076.         [ Links ]

21. Dott, R.H. and J. Bourgeos, 1982. Hummocky stratification: Significance of its variable bedding sequences. Geological Society of America Bulletin, 91: 663-680.         [ Links ]

22. Eide, C.H., J.A. Howell and S.J. Buckley, 2015. Sedimentology and reservoir properties of tabular and erosive offshore transition deposits in wave-dominated, shallow-marine strata: Book Cliffs, USA. Petroleum Geology, 21:55-73.         [ Links ]

23. Enge H.D., J.A. Howell and S.J., Buckley, 2010. The geometry and internal architecture of stream mouth bars in the Panther Tongue and the Ferron Sandstone members, Utah, U.S.A. Journal of Sedimentary Research, 80:1081-1031.         [ Links ]

24. Everett, K.R., 1983. Histosols. In: L.P. Wilding, N.E. Smeck and G.F. Hall (Eds.), Pedogenesis and Soil Taxonomy, II. The Soil Orders, Elsevier Science Publishers, 1-53.         [ Links ]

25. Fielding, C., 2010. Planform and facies variability in asymmetric deltas: facies and depositional architecture of the Turonian Ferron Sandstone in the Western Henry Mountains, south-central Utah, U.S.A. Journal Sedimentary Research, 80:455- 479.         [ Links ]

26. Feruglio, E., 1938. El Cretácico superior del Lago San Martín y de las relaciones adyacentes. Physis, 12:293-342.         [ Links ]

27. Feruglio, E., 1944. Estudios geológicos y glaciológicos en la región del lago Argentino (Patagonia). Boletín de la Academia Nacional de Ciencias, Córdoba, 37:3-255.         [ Links ]

28. Feriglio, E., 1949. Descripción Geológica de la Patagonia. Yacimientos Petrolíferos Fiscales (YPF), I, II, III.         [ Links ]

29. Fildani, A., T.D. Cope, S.A. Graham and J.L. Wooden, 2003. Initiation of the Magallanes Foreland basin: Timing of the southernmost Patagonian andes Orogeny revised by detrital zircon provenance analysis. Geology, 31: 1081-1084.         [ Links ]

30. Fosdick, J.C., B.W. Romans, A. Fildani, A. Bernhardt, M. Calderón and S.A. Graham, 2011. Kinematic evolution of the Patagonian retroarc fold-and-thrust belt and Magallanes foreland basin, Chile and Argentina, 51°30´S. Geological Society of America Bulletin, 123:1679-1698.         [ Links ]

31. Galloway, W.E., 1975. Process framework for describing the morpholofic and stratigraphic evolution of deltaic depositional system. In: M.L. Broussard (Ed.), Deltas, Models for Exploration. Houston Geological Society 87-98.         [ Links ]

32. Ghiglione, M.C., J. Likerman, V. Barberón, L. Beatriz Giambiagi, B. Aguirre-Urreta and F. Suarez, 2014. Geodynamic context for the deposition of coarse-grained deep-water axial channel systems in the Patagonian Andes. Basin Research, 26:726-745.         [ Links ]

33. Ghiglione, M.C., M. Naipauer, C. Sue, V. Barberón, V. Valencia, B. Aguirre-Urreta and V.A. Ramos, 2015. U-Pb zircon ages from the northern Austral basin and their correlation with the Early Cretaceous exhumation and volcanism of Patagonia. Cretaceous Research, 55:116-128.         [ Links ]

34. Gibert, J.M. and J. Martinell, 1993. Controles ambientales sobre la distribución de las paleoicnocenosis en el estuario Plioceno del Baix Llobregat (Barcelona, Cataluya). Revista Española de Paleontología, 8:140-146.         [ Links ]

35. Gugliotta, M. S.S. Flint, D.M. Hodgson, and G.D. Veiga, 2015. Stratigraphic record of river-dominated crevasse subdeltas with tidal influence (Lajas Formation, Argentina). Journal of Sedimentary Research, 85, 265-284.         [ Links ]

36. Isla, M.F., E. Schwarz and G.D. Veiga, 2018. Bedset characterization within a wave-dominated shallow-marine succession: An evolutionary model related to sediment imbalances. Sedimentary Geology, 374:36-52.         [ Links ]

37. Kraemer, P.E. and A.C. Riccardi, 1997. Estratigrafía de la región comprendida entre los lagos Argentino y Viedma (49° 40’– 50°10’ LS), Provincia de Santa Cruz. Revista de la Asociación Geológica Argentina, 52:333-360.

38. Kraemer, P.E., J.V. Ploszkiewicz and V.A. Ramos, 2002. Estructura de la cordillera patagónica austral entre los 46º y 52º S. In: M.J. Haller (Ed.), Geología y Recursos Naturales de Santa Cruz. Relatorio del XV Congreso Geológico Argentino, 353- 364.         [ Links ]

39. Kurcinka C., R.W., Dalrymple and M. Gugliotta, 2018. Facies and architecture of river-dominated to tide-influenced mouth bars in the lower Lajas Formation (Jurassic), Argentina, AAPG Bulletin, 102:885-912.         [ Links ]

40. Leanza, A.F., 1972. Andes Patagónicos Australes. In: A.F. Leanza (Ed) Geología Regional Argentina, 689-706.         [ Links ]

41. Li, W., J.P. Bhattacharya, Y. Zhue, D. Garza and E. Blankenship, 2011. Evaluating delta asymmetry using three-dimensional facies architecture and ichnological analysis, Ferron ‘Notom Delta’, Capital Reed, Utah, USA. Sedimentology, 58:478-507.

42. MacEachern, J.A. and M.K. Gingras, 2007. Recognition of brackish-water trace fossil assemblages in the Cretaceous western interior seaway of Alberta. In R. Bromley, L.A. Buaois, M.G. Mángano, J. Genise, R. Melchor (Eds.), Sediment- Organism Interactions: A Multifaceted Ichnology. Society for Sedimentary Geology, Special Publication 88:149-194.         [ Links ]

43. MacEachern, J.A., K.L. Bann, J.P. Bhattacharya and C.D. Howell, 2005. Ichnology of deltas. In: J.P. Bhattacharya and L. Giosan (Eds.), River Deltas: Concepts, Models and Examples. Society for Sedimentary Geology, Special Publication 83:49-86.         [ Links ]

44. MacEachern, J.A., K.L. Bann, S.G. Pemberton and M.K. Gingras, 2007. The ichnofacies paradigm: high resolution paleoenvironmental interpretation of the rock record. In: J.A. MacEachern, K.L. Bann, M.K. Gingras and S.G. Pemberton (Eds.), Applied Ichnology. Society for Sedimentary Geology, Short Course Notes 52:65-93.         [ Links ]

45. MacEachern, J.A. S.G. Pemberton, M.K. Gingras and K.L. Bann, 2010. Ichnology and Facies Models. In: R.W. Dalrymple and N.P. James (Eds.), Facies Models 4. Geological Association of Canada, St. John’s, Geotext 6:19-58.

46. MacEachern, J.A., K.L. Bann, M.K. Gingras, J.P. Zonneveld, S.E. Dashtgard and S.G. Pemberton, 2012. The ichnofacies paradigm. Developments in Sedimentology, 64:103-138.         [ Links ]

47. Macellari, C.E., C.A. Barrio and M.J. Manassero, 1989. Upper Cretaceous to Paleocene depositional sequences and sandstone petrography of southwestern Patagonia (Argentina and Chile). Journal of South American Earth Science, 2:223-239.         [ Links ]

48. Malkowski, M.A., G.R. Sharman, S.A. Graham and A. Findani, 2015. Characterization and diachronous initiation of coarse clastic deposition in the Magallanes-Austral foreland basin, Patagonian Andes. Basin Research, 29:298-326.         [ Links ]

49. Malkiwski, M.A., T. Schwartz, G.R. Sharmann, Z.T. Sickmann and S.A. Graham, 2017. Stratigraphic and provenance variations in the early evolution of the Magallanes-Austral foreland basin: Implications for the role of longitudinal versus transverse sediment dispersal during arc-continent collision. The Geological Society of America Bulletin, 129:349-371.         [ Links ]

50. Manassero, M.J., 1988. Petrografía y procedencia de las areniscas cretácicas superiores de la Cuenca Austral Argentina. Revista de la Asociación Geológica Argentina, 47:73-82.         [ Links ]

51. Marinelli, R.V., 1998. Reservorios Deltaicos de La Formación Piedra Clavada. Boletín de Informaciones Petroleras, 15:28-37.         [ Links ]

52. Moyano Paz, D., C. Tettamanti and D.G. Poiré, 2016. Análisis de facies, composición y procedencia de las psamitas de la Formación La Anita (Cretácico tardío) en el Cerro Calafate, Santa Cruz. VII Congreso Latinoamericano de Sedimentología and XV Reunión Argentina de Sedimentología, Actas: 122 p.         [ Links ]

53. Moyano Paz, D., C. Tettamanti, A.N. Varela and D.G. Poire, 2018. Estratigrafía y sedimentología de la Formación La Anita, Cuenca Austral, Patagonia, Argentina: Una visión a partir de análisis de facies, paleocorrientes y trazas fósiles. XVI Reunión Argentina de Sedimentología, Actas: 163 p.         [ Links ]

54. Mjøs, R., O. Walderhaug and E. Prestholm, 1993. Crevasse splays sandstones geometries in the Middle Jurassic Ravenscar Group Yorkshire, UK. In: M. Marzo and C. Puigdefáfregas (Eds.), Alluvial Sedimentation, International Association of Sedimentologists, Special Publication 17:167-184.         [ Links ]

55. Myrow, P.M. and J.B. Southard, 1996. Tempestite deposition. Journal of Sedimentary Research, 66:875-887.         [ Links ]

56. Olariu, C. and J.P. Bhattacharya, 2006. Terminal distributary channels and delta front architecture of river-dominated delta systems. Journal of Sedimentary Research, 76:212-233.         [ Links ]

57. Olariu, C., R.J. Steel and A.L. Petter, 2010. Delta-front hyperpycnal bed geometry and implications for reservoir modeling: Cretaceous Panther Tongue delta Book Cliffs, Utah. The American Association of Petroleum Geologists, 94:819-845.         [ Links ]

58. Pankhurst, R.J., T.R. Riley, C.M. Fanning and S.P. Kelley, 2000. Episodic silicic Volcanism in Patagonia and Antartic Peninsula: Chronology of magmatism associated with the break-up of Gondwana. Journal of Petrology, 41:605-625.         [ Links ]

59. Perez-Arlucea, M. and N.D. Smith, 1999. Depositional patterns following the 1870s avulsion of the Saskatchewan River (Cumberland Marshes, Saskatchewan, Canada). Journal of Sedimentary Research, 69:62-73.         [ Links ]

60. Peroni, G., M. Cagnolatti and M. Pedrazzini, 2002. Cuenca Austral: marco geológico y reserva histórica de la actividad petrolera. In: M. Schiuma, G. Hinterwimmer, and G. Vergani (Eds.), Simposio Rocas Reservorio de las Cuencas Productivas de la Argentina. V Congreso de Exploración y Desarrollo de Hidrocarburos, 11-19.         [ Links ]

61. Plint, A.G., 2010. Wave- and storm-dominated shoreline and shallow-marine systems. In R.W. Dalrymple and N.P. James (Eds), Facies models 4, Geological Association of Canada, 167- 200.         [ Links ]

62. Reineck, H.E. and I.B. Singh, 1980. Depositional Sedimentary Environments: With Reference to Terrigenous Clastic. Springer- Verlag, New York, 549 pp.         [ Links ]

63. Retallack, G.J., 2001. Soils of the past: An introduction to Paleopedology, Second Edition. Blackwell Science, Oxford, 404 pp.         [ Links ]

64. Riccardi A.C. and E.O. Rolleri, 1980. Cordillera Patagónica Austral. In J.C.M. Turner (Ed) Segundo Simposio de Geología Regional Argentina. Academia Nacional de Ciencia II, 1173- 1304.         [ Links ]

65. Riccardi A.C., 1983. Informe paleontológico de los perfiles Estancia Alta Vista, Arroyo El Turbio. Inedit report of Yacimientos Petrolíferos Fiscales (YPF).         [ Links ]

66. Richiano, S., A.N. Varela, A. Cereceda and D.G. Poiré, 2012. Evolución paleoambiental de la Formación Río Mayer, Cretácico inferior, Cuenca Austral, provincia de Santa Cruz, Argentina. Latin American Journal of Sedimentology and Basin Analysis 19:3-26.         [ Links ]

67. Richiano, S., D.G. Poiré and A.N. Varela, 2013. Icnología de la Formación Río Mayer, Cretácico inferior, sudoeste de Gondwana, Patagonia, Argentina. Ameghiniana, 50:273-286.         [ Links ]

68. Richiano, S., A.N. Varela, L.E. Gómez-Peral, A. Cereceda and D.G. Poiré, 2015. Composition of the Lower Cretaceous source rock from the Austral Basin (Río Mayer Formation, Patagonia, Argentina): Regional implication for unconventional reservoirs in the Southern Andes. Marine and Petroleum Geology, 66:764-790.         [ Links ]

69. Robbiano, J.A., H. Arbe and A. Bangui, 1996. Cuenca Austral Marina. In: V.A. Ramos and M. Turic (Eds.), XII Congreso Geológico Argentino and Congreso de Exploración de Hidrocarburos, 343-358.         [ Links ]

70. Rodríguez, A.B., M.D. Hamilton and J.B. Anderson, 2000. Facies and evolution of the modern Brazos Delta, Texas: wave versus flood influence. Journal of Sedimentary Research, 70, 283- 295.         [ Links ]

71. Rodríguez, J. and M. Miller, 2005. Cuenca Austral. In: Frontera Exploratoria de la Argentina. VI Congreso de Exploración y Desarrollo de Hidrocarburos, 307-324.         [ Links ]

72. Sickmann, Z.T., T.M. Schwartz and S.A. Graham, 2018. Refining stratigraphy and tectonic history using detrital zircon maximum depositional age: an example from Cerro Fortaleza, Austral Basin, southern Patagonia. Basin Research, 30:708- 729.         [ Links ]

73. Sømme, T.O., J.A. Howell, G.J. Hampson and J.E.A. Storms, 2008. Genesis, architecture, and numerical modeling of intra-parasequence discontinuity surfaces in wave-dominated deltaic deposits: Upper Cretaceous Sunnyside Member, Blackhawk Formation, Book Cliffs, Utha, U.S.A. In: G.J. Hampson, R.J. Steel, P.B. Burgess and R.W. Dalrymple (Eds.), Recent Advances in Models of Siliciclastic Shallow-Marine Stratigraphy. Society for Sedimentary Geology, Special Publication, 90:421-441.         [ Links ]

74. Taylor, A.M. and R. Goldring, 1993. Description and analysis of bioturbation and ichnofabric. Journal of the Geological Society of London, 150:141-148.         [ Links ]

75. Tettamanti, C., D. Moyano Paz, A.N. Varela, L.E. Gómez- Peral, D.G. Poiré, A. Cereceda and L.A. Odino, in press. Sedimentology and stratigraphy of the uppermost Cretaceous Continental Deposits of the Austral-Magallanes Basin, Patagonia, Argentina. Latin American Journal of Sedimentology and Basin Analysis, Special Publication, in press.         [ Links ]

76. Varela, A.N., 2015. Tectonic control of accommodation space and sediment supply within the Mata Amarilla Formation (lower Upper Cretaceous) Patagonia, Argentina. Sedimentology, 62:867-896.         [ Links ]

77. Varela, A.N., D.G. Poiré, T. Martin, A. Gerdes, F.J. Goin, J.N. Gelfo and S. Hoffmann, 2012a. U-Pb zircon constraints on the age of the Cretaceous Mata Amarilla Formation, Southern Patagonia, Argentina: its relationship with the evolution of the Austral Basin. Andean Geology, 39:359-379.         [ Links ]

78. Varela, A.N., G.D. Veiga, and D.G. Poiré, 2012b. Sequence stratigraphic analysis of Cenomanian greenhouse palaeosols: A case study from southern Patanoia, Argentina. Sedimentary Geology, 271-272: 67-68.         [ Links ]

79. Varela, A.N., L.E. Gómez-Peral, S. Richiano and D.G. Poiré, 2013. Distinguishing similar volcanic source areas from an integrated provenance analysis: implication from foreland Andean basins. Journal of Sedimentary Research, 83:258-276.         [ Links ]

80. Varela A.N., M.S. Raigemborn, S. Richiano, T. White, D.G. Poiré and S. Lizzoli, 2018. Late Cretaceous paleosols as paleoclimate proxies of high-latitude Southern Hemisphere: Mata Amarilla Formation, Patagonia, Argentina. Sedimentary Geology, 363:83-95.         [ Links ]

81. Wright L.D., 1977. Sediment transport and deposition at river mouths: a synthesis. Journal of Sedimentary Research, 70:788- 802.         [ Links ]

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