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Sedimentary rocks are our window to understand the history and evolution of the surface of our planet. The sedimentary record, although biased by variable preservation conditions and post depositional processes, potentially preserve signals of the interaction between physical, chemical and biological processes that takes place at the interface between the Geosphere, the Hydrosphere/ Atmosphere and the Lithosphere. Geochemistry, integrated with Sedimentology, has become a standard approach to unravel these interactions and to provide some insights for the understanding of how sedimentary geochemistry is preserved within different sedimentary environments. Microbial life is ubiquitous at the Earth’s surface (Whitman et al., 1998), and has been present throughout our Planet’s history. It has evolved to exploit the energy provided by gradients in geochemical composition between rocks, organic materials and surface fluids, using this energy for maintenance and growth (Hoeler, 2007). Due to their abundance, chemical reactivity and metabolic activity (Konhauser, 2007), microbes play a central role in biogeochemical cycles (C, O, N, S, Fe, etc) at both, micro and macroscopic scales (Schlesinger and Bernhardt, 2020). The best example of these processes are the current chemical composition of our O2-rich atmosphere or the chemical redox gradients that exist at the sediment-water interface in most sedimentary environments around the world, where early diagenesis driven by organic matter degradation takes place (Aller, 2014). In addition, microbial mats and biofilms influence the precipitation/dissolution of minerals such as carbonates (explaining the the abundance of microbialites in the ancient rock record, Riding, 2011) as well as the rheological and mechanical behaviour of detrital sediments, where a classic example are known as MISS (Microbially induced sedimentary structures, Noffke et al., 2010). For these reasons, whenever we talk about sedimentary geochemistry we are actually talking about sedimentary biogeochemistry and geomicrobiology. This is so since microbial activity has been shaping the surface chemistry and composition of our planet, as previously recognized by the pioneering work of Vladimir Vernadsky in 1926 and later by Lourens Baas-Becking in 1934 (Knoll et al., 2012). Vernadsky and Baas-Becking early ideas have grown and become the lens through which we scientifically observe our world, making it clear that the Biosphere adds another layer of diversity and complexity in order to understand our planet as a system.

The genus Leocrates is currently made up of 11 nominal species, of which Leocrates chinensis Kinberg, 1866 is the type species. Kinberg's original description is brief, and the diagnostic morphological characters are poorly defined. Therefore, numerous subsequent records in different world regions have been considered doubtful. Numerous specimens of Leocrates collected by SCUBA diving in various locations of Robinson Crusoe Island (33°37'S, 78°51'W) in the Juan Fernández Archipelago, between 4 and 10 m depth were examined and determined as a new species herein named Leocrates ernstehlersi n. sp. It is characterized by the size of anterior and posterior eyes, the median chaetigers with scarce notochaetae and neurochaetae per bundle; neurochaetal blades are 4-14 times longer than wide and neuracicular lobes slightly longer than wide. A key to identifying species of Leocrates having large anterior eyes and anterior eyes/prostomial width ratio between 1/4 to 1/8 is also included.

The well-preserved limestone succession, Loma Negra Formation (~40 m), in the Tandilia System was deposited in a shallow carbonate ramp under low energy conditions. The evolution in the depositional settings of the unit was indicated as deepening upwards varying from shallow-middle to outer ramp environment. The limestone fabric is assumed as the product of biologically controlled precipitation of micrite, where the terrigenous supply was limited. From detailed meso- and microscopic descriptions it is possible to recognize microbially induced sedimentary structures ‘MISS’ represented by typical microtextures related to microbial activity that appear represented throughout the entire formation. In addition, micro-stromatolites are observed in the unit associated with the microbial mats showing micro-columnar conical to domical morphologies. In the basal and middle Loma Negra Formation, hemispherical structures are recognized in the bed-tops and interpreted as bubbles-like and gas escape features associated with the microbial mat interaction. Their morphology is compared with oxygen bubbles produced by modern experimental modelling with photosynthetic cyanobacteria microbial mats. Moreover, hemispherical structures are associated with increasing gas pressure lifting grains and the organic components to the surface.  This paper provides evidence to understand the possible causal relationship between microbial activity and seawater oxygenation. The high oxygen production revealed by geochemistry proxies and here proposed as probably associated with photosynthetic microbial activity might be a plausible explanation for the record of the documented Middle Ediacaran Oceanic Oxygenation Event in the Loma Negra Formation.  

The northeast of Santiago del Estero province is located in the northwestern edge of the BajosSubmeridionalesbasin (BBSS), in the distal area of the Salado river mega-fan (Fig. 1a). The pre-alluvial substrate in this sector of the Chaco plain is composed by the quartzite sandstones of the Las Piedritas Formation. According to the sedimentary model proposed by Iriondo (1990), the parent materials of the soils are of aeolian, lacustrine and fluvial origin. The genesis of these materials is linked to climatic variations and the neotectonic activity of the Quaternary. The aeolian sediments in the area would correspond to the loess of the Urundel Formation (Iriondo, 1990), which has been characterized by abundant quartz and absence of volcanic glass in the coarse fractions, and illite in the clay fraction.On the other hand, recent studies in the northeast of Santiago del Estero province revealed the presence of pedosediments, which were identified through micromorphological, mineralogical, chemical and physical analyses (Moretti et al., 2020). Unlike the Urundel Formation, soils and pedosedimentary parent materials show different proportions of volcanic glass in the sand fraction, while the clay fraction is composed of illite, kaolinite, and illite-smectite interlayer minerals, among other characteristics. Given the differences in mineralogy and origin between the mentioned sedimentary materials, the aim of this work is to improve the knowledge of the origin of the parent materials and their influence in the soil genesis in this region, through the mineralogical study of the sand fraction. Five soil profiles developed in different landscape positions were studied: an EnticHaplustoll (C-50) and a TypicHaplustoll (C-73) in the alluvial bajada unit; aTypicArgiustoll (C-16) in the slope unit; a TypicHaplustert (C-53) in the flood-plain unit; and a TypicEndoacuert (C-27) in the drainage network (Fig. 1b).The qualitative and quantitative mineralogical study was carried out on the most representative sand fraction (very fine sand: 50-100 µm) by means of optical polarization microscopy. The analysis and interpretation of the mineralogical data was complemented by other previous analytical data (Moretti et al., 2020): granulometry, cation exchange capacity of the clay fraction (CICarc), micromorphology on thin sections, and specific mass magnetic susceptibility (?).The results obtained (Table 1), allowed to identify a paleosurface (P) at the base of the profiles, and two overlying depositional units (UD). UD I includes the pedosediment and UD II consists of a few centimeters thick fine-grained material. A transitional level (UD I-P) between the paleosurface and the pedosedimentwas also differentiated. For all the profiles, the identified minerals were quartz, feldspars, alterites, acid volcanic glass, micas, hornblendes and pyroxenes, in addition to silt-clayey micro-aggregates (pseudo-sands) and grains coated with clay and iron oxides (Fig. 2c; d; e; f y Fig. 3a; b; c; d). In each case, their percentages vary both within the same profile and between profiles, with different trends according to the soil-landscape unit. In the alluvial bajada, the Ap horizons (UD II) of both soils (C-50 and C-73) are characterized by lower contents of volcanic glass than those of the UD I; besides, a high proportion of hornblende is observed in the Ap of the EnticHaplustol. In the pedosediment (UD I), the percentage of volcanic glass increases, and then decreases towards the base of the profiles (P and UD I-P). At the paleosurface level (P), ferromagnesian minerals are very scarce, while quartz increases reaching the maximum values. In correspondence with the decrease of the ferromagnesian minerals, the ? values also decrease towards the base of the profiles. This co-variation suggests that the first magnitude differences in the magnetic signal are related to the mineralogical composition of the parent material. On the other hand, the highest proportion of pseudo-sands and clay-coated grains -as in almost all the profiles- is observed in the pedosediment (UD I). These pseudo-sands and clay-coatings imply an underestimation of the fine fraction content obtained in the granulometric analysis of these materials, which is also revealed by the high and anomalous CICarc values (>100 cmol+.kg-1). A greater degree of alteration of feldspars and the presence of sub-rounded quartz grains covered with iron oxides has also been observed (Fig. 3a; b). This fact also suggests that thismaterial would have been affected by one or more previous cycles of pedogenesisand erosion. The soil studied on the slope (C-16), has the highest content of volcanic glass in the pedosediment (UD I), together with the highest content of ferromagnesian minerals, micas and feldspars. Pseudo-sands increase with depth and decrease at the base of the profile (UD I-P). Surface UD II has not been identified in this soil, which may have been eroded from the slope. Here, the value of ? is also higher at UD I than at the base of the profile, in relation to its higher proportion of ferromagnesian minerals. The Vertisol located in the flood-plain landscape unit (C-53) shows similar mineralogical characteristics than the soils of the alluvial bajada (C-50 and C-73). On the contrary, the Vertisol found in the drainage pathway (C-27) presents a vertical distribution of the components of the coarse fraction that differentiates it from the rest of the profiles in the toposequence. This profile has the highest contents of mica in UD II (Ap-Bt-Btss1), and the highest values of volcanic glass in the UDI(2Btss2-2Bt). It also has a low proportion of pseudo-sands and clay-coated grains throughout the profile, which correlates with low CICarc values. It is interpreted that in this profile the pseudo-sands were not preserved due to the particular hydric conditions in this position of the landscape, the effects of expansion-contraction and the greater degree of soil development. In this profile, higher contents of ferromagnesian minerals have been identified in the UD I and II interface (Btss1 and 2Bt horizons),together with an increase in the ? values. Results suggest a model of landscape-soil evolution that could be related to the environmental changes of the Quaternary in the region. Climatic oscillations and tectonic dynamics during the Late Pleistocene led to readjustment in the hydrographic network of the Salado River, which would have promoted erosion processes of paleosurfaces (P) and generating pedosediments (UD I). The paleosurfaces (P), with high quartz and very low volcanic glass contents, would be related to the sediments of the Salado River and with the quartzite sandstones of the Las Piedritas Formation.The pedosediment (UD I), characterized by the high content of pseudo-sands, would have been enriched in minerals of volcaniclastic origin, which are very scarce in the paleosurface (P). This mineralogical association relates these eolian contributions to the Tezanos Pinto Formation, which covers the landscape in the southern sector of the BBSS basin. Depositional unit II (UD II) is composed of intermediate quartz and volcanic glass contents, and by high mica and hornblendes contents. This unitwould correspond to a youngereolian event that covered the sub-basin surface, probably during some of the arid cycles of the Holocene. This material is not present on the slope unit of the studied sub basin, since it was probably removed by erosion. Finally, under a more humid climate and in a geomorphologically more stable environment, the pedogenesis of these deposits occurred.

There are different forms of coastal erosion management: do nothing, accommodation (adaptation or relocation), and protection (soft and hard solutions; Williams et al., 2018). On the coast of the province of Buenos Aires, Argentina, several of the above techniques have been used, i.e. armoring, moderation and restoration, especially in the city of Mar del Plata (General Pueyrredón country). The beaches in front of the central part of the city have a large number of breakwaters. Those structures, which were built without an adequate design, favored the migration of erosive processes downdrift, i.e. in the direction of the coastal sediment transport (south to north). Other protection works that were carried out are the beach nourishment projects that use sands extracted from different sources, both marine and continental. The most relevant work was carried out in 1998 with sand extracted from the sand shoal accumulated at the outlet of the port. The beaches located in the southern part of the city are almost natural and only in recent years a few protection structures, such as groins and rip-rap revetments of orthoquartzite rocks have been emplaced. Because of this, the southern area is preserving a high degree of landscape and sanitary quality for bathing purposes. The study area is located at the southern end of the General Pueyrredón country, within a protected area named Reserva Turística y Forestal Paseo Costanero Sur, which has an extension of 27 km from the Punta Mogotes lighthouse to the Las Brusquitas creek (Fig. 1c). The area has a great variety of landforms: pocket beaches, dune fields, tall cliffs, at places covered with fossil dunes, and rock platforms. A feature of oceanographic interest is the existence of a littoral cell in the Ensenada de Mogotes (northernmost part of the study area). These beaches are susceptible to storms, mainly approaching from the south, that causes coastline and cliff retreat, generating a risk for the neighborhoods and for the stability of the route 11 that runs on top of these cliffs. Likewise, this provincial route between the cities of Mar del Plata and Miramar, in the sector near the San Eduardo del Mar neighborhood, is affected by the migration of dunes under the action of winds blowing from WSW. It is often required the intervention of the municipality to rehabilitate the route. Such sands are usually not reintegrated to the coastal sediment budget, despite the fact that there have been carried out in recent years different studies recommend that for a sustainable management (Fig.1). The objective of the present work was to analyze the possible use of the sands accumulated by the wind on the Provincial Route 11 in the vicinity of the San Eduardo del Mar neighborhood to carry out artificial nourishments at the beaches belonging to the Reserva Turística y Forestal Paseo Costanero Sur, i.e. Playa Serena, Luna Roja, Chapadmalal and San Eduardo del Mar beaches (Fig.1). Beach nourishment is considered a soft protection solution consisting in the artificial fill of the beach using sand (“borrow sand”) from another site. The purpose is to increase the width of the backshore and thus to keep the toe of the cliffs away from the action of the waves. This method also provides recreational benefits by increasing the tourist capacity and, therefore, the associated economic value for local municipalities. The methodology used for this work was divided into two parts: on the one hand, a survey of the beaches was carried out by means of topographic profiles with an analog theodolite during low tide conditions to determine the beach width and slope. At the same time, four sediment samples were obtained from a depth of one centimeter (respect to the surface of the beach), and then sieved in laboratory to determine the average grain size and statistical parameters (Folk and Ward, 1957) using the Gradistat software (Blott and Pye, 2001). On the other hand, the suitability of natural and borrow sediments was checked by applying the James diagram (1975). Using the statistical parameters, the Overfill factors (Ra) value, which indicate the suitability (and therefore the probable behavior) of the borrow material respect to the native material, were calculated; and the Renourishment factor (Rj), which indicates how often the replenishment of the borrow material would be required (U.S. ACE, 1984). For the eolian sands of the dune field, the grain size data were obtained from previous sampling (García González et al., 2021). Table 1 summarizes the results of the beach profiles and grain-size parameters for each beach. In general, beach lengths range from 40 to 70 m, slopes from 3 % to 5 % and the grain sizes are quite varied, from fine sands to gravel sizes (2 phi to -2.5 phi). Applying the James (1975) diagram, it was found that the best combination was the one corresponding to the replenishment of Playa Serena. In other words, only 1.02 m³ of borrow material (i.e. sand from the mobile dunes) is needed to replenish 1 m³ of native sand in that beach, and it had to be replenished 0.14 times more often respect to the present material. The rest of the beaches gave interesting results: for Chapadmalal and San Eduardo del Mar beaches the Ra ratios were also small (Ra: 1.05 and 1.02, respectively and Rj: 1.5), while Luna Roja had the highest values (Ra: 5.0 and Rj: 2; Table 3). The results presented above allowed the following conclusions: Comparing sediment compositions in the Ensenada de Mogotes fine sand sizes prevail (Playa Serena 2.5 phi) while the grain sizes become coarser and with a smaller selection (San Eduardo del Mar 0.5 phi) outside of the Ensenada. According to the topographic profiles, the beaches farther away from the Ensenada present steeper slopes (i.e. 5 %, Luna Roja and San Eduardo del Mar) with biggest grain sizes. Chapadmalal beach is an exception because it is a bimodal beach related to a breakwater. The diagrams of James showed that the aeolian sands of the San Eduardo del Mar dunes can be used as borrow sediment to nourish the beaches within the protected area Reserva Turística y Forestal Paseo Costanero Sur. Results from the Ra and Rj diagrams allowed to state that borrow sand (obtained from mobile dunes) is especially to the Playa Serena sands (Ra 1.02 and Rj 0.14) and renourishments values are also suitable for the beaches of Chapadmalal and San Eduardo del Mar. Considering the distance between the borrow area (the mobile dunes) and the beaches, San Eduardo del Mar and Chapadmalal are the most adequate to avoid large transportation costs, because the first one is located very close to dune field and the second one is only 5.3 km away.

This work provides new U-Pb detrital zircon ages of the eastern synorogenic Upper Cretaceous deposits of the Neuquén Basin at Paso Córdoba, Río Negro, Argentina (Fig. 1). The Neuquén Basin is a large depocenter developed during the Late Triassic to Paleogene along the southwestern margin of Gondwana (30-40°S). It originated by continental-scale rifting processes resulting in the break-up of the Pangea supercontinent. It records a thick Mesozoic sedimentary succession more than 7,000 m thick including marine and non-marine sedimentary rocks. Important geodynamic changes occurred during the latest Mesozoic with the accelerated westward movement of the South American plate following its separation from the African plate, and the continuation of subduction processes along its western margin, most notably the convergence between the Nazca-Farallón and the South American plates. This new compressive tectonic setting triggered the foreland basin deposition of the Neuquén Group. The non-marine Neuquén Group shows an important regional distribution and is characterized as the first foreland basin deposits linked with the early uplift of the Andean orogen at ca. 100 Ma. The Neuquén Group contains an important fossil record and is a reservoir rock in some depocenters of the basin. For this reason, it has been a well-studied unit in both the southern and central parts of the basin. Regionally, this stratigraphic unit is covered by Maastrichtian to Paleocene marine facies of the Malargüe Group. The Upper Cretaceous non-marine deposits of the Neuquén Basin have an important exposure in Paso Córdoba area (General Roca, Río Negro). According to Hugo and Leanza (2001), these deposits are included in the Bajo de la Carpa and Anacleto formations (Neuquén Group) and the overlying Allen Formation (Malargüe Group). These authors interpreted the contact between both groups as an erosional unconformity. Afterwards, Paz et al. (2014) and Díaz-Martínez et al. (2018) carried out detailed sedimentological and ichnological studies in the area, discussed the contact between both units and proposed a transitional passage between the Anacleto (lacustrine/fluvial facies) and Allen (aeolian facies) formations. The ages of the Anacleto and Allen formations are based on magnetostratigraphic and biostratigraphic data obtained in other localities to the west and north of the study area. Dingus et al. (2000) proposed an early-middle Campanian maximum depositional age for the Anacleto Formation (78.3 Ma) based on paleomagnetic studies in the Auca Mahuevo area (Neuquén). Furthermore, levels assigned to the overlying Allen Formation in the Lago Pellegrini area (Río Negro), contain an ostracod fauna from the upper Campanian-lower Maastrichtian interval (Ballent, 1980). In this contribution, we use a sedimentological and geochronological approach to discuss the paleoenvironment, provenance and age of the Anacleto Formation in the Paso Córdoba area. The facies analysis carried out in this work corroborates the proposal made by Paz et al. (2014) and by Díaz-Martínez et al. (2018), allowing the recognition of three facies associations: (I) lacustrine, (II) wet interdunes and (III) dunes and dry interdunes (III), indicating an increase in the aridity of the depositional system towards the top of the studied succession. In particular, the sample APC01-20 dated by U-Pb in detrital zircons was collected from the bottom of wet interdunes facies association (II) given its textural features and its importance in terms of their stratigraphic position (Fig. 1D and 2D). According to the frequency histogram and relative probability plot of detrital zircon ages obtained from APC01-20 sample analysis, a multimodal pattern of ages can be distinguished. The sample is represented by five main populations; 75 – 126 Ma (Cretaceous, 32%), 150 – 200 Ma (Jurassic, 31%), 254 – 282 Ma (Permian, 10%), 300 – 349 Ma (Carboniferous, 14%) and 358 - 405 Ma (Devonian, 11%). The sample also contains two isolated ages that represent 2% of the total (478 Ma, Ordovician and 1,217 Ma, Mesoproterozoic). The main peak (32%) corresponds to latest Early-Late Cretaceous zircons with a youngest graphical peak (YPP) of 81.9 Ma (Campanian) (Fig 2A). For the calculation of the maximum depositional age, different ways of measurement were considered (Dickinson and Gehrels, 2009). As a result of data analysis, weighted mean average of the youngest cluster of two or more grain ages that overlap at 1? uncertainty, was the estimation that was better adjusted for the sample. The age calculation based on a sample of young Cretaceous zircons (n=11) pointed towards a maximum depositional age of 78.6 ± 1.7 Ma (middle Campanian) for the Anacleto Formation. The number of zircons used for the calculation of the maximum depositional age, together with the morphology of the measured crystals, suggest a coeval volcanic activity during the deposition of Anacleto Formation.

Dear LAJSBA readers, this editorial note has the intention to updateyou with the news from our journal. In this sense, we want to tell you that our editorial team has been renewedwith the incorporation of two Associate Editors, José I. Cuitiño(CONICET, Argentina) and Giorgio Basilici (UNICAMP, Brazil). We want to express deeply thanks to RenataNetto and Fernando Gómez for the excellent work doneduring the last four years.We also express our gratitude to the Board of the Asociación Argentina de Sedimentología for trusting us for this importantand committed task. The journal, since its foundation in 2005 (coming from the AAS Revista since 1994), has been progressively improving its quality and its visibility within the scientific community. LAJSBA is an entirelyonlinefree-access journal witha highlevel scientific quality and designwhich is recognized bythe Latin American Earth Sciences community. In terms of bibliographic indexes, LAJSBA is included in the ranks of SCOPUS, Scimago, Latindex, DOAJ, GeoRef,andSciELO. Some important news can be highlighted from the last two years.Firstly, we want to communicate a great improvement for our journal: the launch of the new LAJSBA website!This website (https://lajsba.sedimentologia.org.ar/index.php/lajsba) represents a great advance for the journal and concentrate not only thesubmission and review systems, but also the repository ofthe complete collection of LAJSBA.This achievement was possible thanks to the support of the members of the AsociaciónArgentina de Sedimentología and we are proud to share it with the entire Latin Americangeoscientist community and from every corner of the world where LAJSBA has a reader. The second essential notice is that, since the volume 26.2 (December 2019) the journal is on regular time! This was possible through the efforts of authors, reviewers and editors, which hardly worked during the last four years. One benefit of the present onlinepublication system is the possibility to manage several volumes in progress in our online platform;this meansthat after the paper acceptance, it will be automatically published as part of future volumes, reducing considerably the time for online publication. Finally, a great news for our sedimentological community is related tothe latestmodification from Scimago Journal Ranking, whichrankedthe journal in the 2nd Quartile in all the categories where it is included (Geology, Paleontology, and Stratigraphy). This was the result of the high visibility gain for LAJSBA which could be interpreted from the statistics in the Scimago web page, where our journal reached in 2021 the record of cites in the last 15 years! We are convinced that maintaining the path marked by previous editorial teams, together with the recent improvements of bibliographic indexes andan active international diffusion,LAJSBAwill increasingly become an attractive journalfor the communication of scientific advances of the Sedimentology and Basin Analysisscientific community.To conclude, we want to emphasize that the future of LAJSBA depends uponthe support of the Latin American sedimentological community, including readers, authors, reviewers, and editors, not just to maintain its importance in our region, but to cross our borders.We repeat once again the message to our readers; we are looking forward to receiving your contributions!

Transitional marine systems are affected by the interaction of wave, tidal and fluvial processes, with different impacts on salinity, turbidity, energy and depositional rate. Benthic organisms are influenced by these processes, and so, the ichnological signatures of these deposits represent key elements for environmental analysis. The Lajas Formation (Middle Jurassic, Neuquén Basin Argentina) is characterized by deposits accumulated in shallow transitional marine environments, mainly deltaic systems. A detailed study of sedimentological and ichnological features of the Lajas Formation developed on subsurface core samples allows to reconstruct the depositional conditions and evolution of unit and determine that the prevalent processes on the reworking of the sediments is fluvial, with subordinated wave processes. Fourteen sedimentary facies were defined, grouped into five facies associations: interdistributary plain, distributary channels, fairweather and storm-generated waves bars, delta front mouth bars, and prodelta. The ichnological analysis allows to differentiate 21 trace fossils: representing 5 ichnofacies: Skolithos (Mararonichnus suite), Skolithos (or Rosellia), impoverished Cruziana, Cruziana, Scoyenia and Zoophycos. Two surfaces with Glossifungites suites were recognized, and they are interpreted in two different ways, one related to authigenic changes and the other as a surface of stratigraphic importance, related to the variation in sea level. Finally, the whole section studied constitutes a prograding fluvio-dominated deltaic system, representing a Highstand System Tract, with minor transgressive events.

Typically, the stratigraphic record of syn-eruptive fluvial successions is a pyroclastic-rich one. It includes an alternation of braided channel deposits and sheet-like floodplain strata, in which the occurrence of paleosols with in situ trees and primary pyroclastic deposits is common. The participation of facies formed from sediment-laden flows is also a conspicuous feature in these successions. Nevertheless, the disturbances occurred in the chilean Blanco River in 2008, as a consequence of the large tephra influx from the Chaitén Volcano eruption, result in discrepancies with the mentioned conceptual background including the plan-view form and filling of channels, and lateral compositional changes along the river. These discrepancies would response to local conditions such as precipitation, vegetation, topography, and type and amount of available sediment. Furthermore, the connection between the Blanco River and the Pacific Ocean, adds an additional feature to syn-eruptive fluvial successions, represented by associated delta plain deposits composed of volcaniclastic sands.