Alfonso Encinas

Verified

Alfonso verified their affiliation via an institutional email.

Learn more

Verified

Alfonso verified their affiliation via an institutional email.

Learn more

• PhD
• Titular Professor at University of Concepción

The late Eocene to earliest Miocene volcanic arc of the Southern Central Andes (33-40°S) and North Patagonian Andes (40-44°S) exhibits distinctive features that shed light on the dynamics of subduction-related volcanic activity in extensional tectonic settings. This period is particularly significant in the Andes, as it records the opening of forea...

The article is accesible in the page of AJS with the doi number. ABSTRACT. The south-central Chile and Argentina margin experienced a regional phase of extensional tectonics during the Oligocene-early Miocene, forming several basins across the forearc, Andean Cordillera, and retroarc regions. These basins accumulated thick successions of volcanic...

Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous. It has been proposed that the preceding Jurassic-Early Cretaceous extensional regime that resulted in a low-relief volcanic arc and the backarc Neuquén basin came to an end, giving way...

En esta contribución se presentan los avances en la construcción de un esquema holoestrátigráfico para el Tithoniano-Berriasiano en la Cuenca Neuquina. El Tithoniano-Berriasiano está representado en la cuenca por la Formación Vaca Muerta y sus equivalentes laterales: formaciones Carrín Curá, Picún Leufú, Quintuco, Bajada Colorada, Lindero de Piedra...

Here, we studied several Pachyrukhinae (Mammalia: Notoungulata: Typotheria: Hegetotheriidae) fossils recovered from the late Early Miocene (Santacrucian SALMA) beds of the Cura-Mallín Formation at the Laguna del Laja (Biobío Region, Chile). The specimens are referred to a new species of the genus Pachyrukhos Ameghino, 1885, P. ngenwinkul sp. nov. T...

The Middle Jurassic‐Early Cretaceous evolution of the Neuquén Basin is traditionally attributed to a long phase of thermal subsidence. However, recent works have challenged this model. In view of this, we study the Late Jurassic Tordillo Formation, a nonmarine depositional unit that marks a shift to regional regression across the basin. Previous st...

Los primates platirrinos constituyen un grupo ecológicamente importante en la Región Neotropical, pero su registro fósil es notorio por su escasez. En Chile, se conocen solo tres fósiles neógenos: el cráneo de Chilecebus de Río Las Leñas (SGO.PV.3213), un astrágalo de Río Cisnes (SGO.PV.974), y un diente aislado de Lonquimay (SGO.PV.22204). Aquí pr...

This work presents new biostratigraphic data based on calpionellids and calcareous dinoflagellate cysts for the Tithonian in Central Chile. This stratigraphic interval is mostly represented by a thick marine succession of limestone and sandstone known as Baños del Flaco Formation. This formation originated in the shallow-water setting of a carbonat...

The Río Damas Formation is an Upper Jurassic volcano-sedimentary succession, whose outcrops are largely distributed between 33°S and 35.30°S in Chile and Argentina, as part of the retroarc Neuquén Basin fill. This unit was deposited during an important marine regressive phase of the basin. We studied the Río Damas Formation exposures at the Los Gat...

Orogenic belts like the Andes experience several changes during long-term evolution of the subduction margin; however, the degree to which their different components (the fore-to-retroarc domains) are jointly or separately deformed is not well understood. To investigate this problem, we provide new field and seismic data of the Chilean forearc at t...

Despite recent efforts, the diversity of Neogene mammals in Chile remains poorly known, with several presumed new taxa awaiting description. For example, previous studies have suggested that the early to late Miocene mammalian assemblages from the Laguna del Laja fossiliferous locality (Cura-Mallín and Trapa-Trapa formations), in the Andean Cordill...

An approximately 3500 m thick stratigraphic section was detailed surveyed in order to study the tectono-sedimentary evolution of the Ñirihuau Formation along the Arroyo Las Bayas, in the northern sector of the Ñirihuau basin, North Patagonian Andes. A total amount of 29 lithofacies were recognized and used to define facies, grouped into six facies...

The tectonic opening of the Tasmanian Gateway and Drake Passage represented crucial geographic requirements for the Cenozoic development of the Antarctic Circumpolar Current (ACC). Particularly the tectonic complexity of Drake Passage has hampered the exact dating of the opening and deepening phases, and the consequential onset of throughflow of th...

The forearc of south-central Chile (36°30′-42°S) is characterized by the presence of a Coastal Cordillera and a low lying area known as the Central Depression. The origin of these morphostructural units has been largely debated. They have been ascribed to different ages between the Cretaceous and the Pliocene, and tectonic causes that involve exten...

During Mid-Cenozoic times, voluminous and genetically heterogeneous volcanism took place across North Patagonia in response to a period of plate tectonic reorganization. One of these volcanic associations is represented by the El Maitén Belt, located to the east of the main Andes for over ∼300 km. This volcanic belt reflects the evolution of a cont...

Geochemical variations in arc- and within-plate magmatic associations since Late Cretaceous times are analyzed and correlated with the main tectonic changes that influenced the Neuquén Basin evolution. The collision and southward migration of the Farallon-Aluk mid-ocean ridge along the Chilean trench since 80 Ma have played an important role in con...

The tectonic regime associated with the Oligo-Miocene Cura-Mallín Formation and equivalents in the Main Andean Cordillera between 35° and 40° S, the Ventana and Abanico formations to the south and north, respectively, is still matter of debate. While most authors have agreed in relating them to an extensional regime that could have interrupted Ande...

Geochemical and geochronological data reveal that late Oligocene‐early Miocene time is a break point in the evolution of Andean magmatism. The Patagonian Andes registered the onset of arc volcanism since the late Eocene forming part of the El Maitén Belt, whose development was driven by the subduction of the Farallon/Nazca plates beneath the Andean...

The Cura Mallín Fm comprises Oligo-Miocene (24-12 Ma) volcanosedimentary rocks covering the axis of the Southern Central Andes of Argentina and Chile (36°-39°S). The tectonic mechanism for deposition of this unit is still matter of debate. There are two contradictory proposals: while some authors have proposed an extensional regime (Jordan et al. 2...

link to a video about this paper in spanish: https://www.youtube.com/watch?v=1Gii9T8JuNc Decoding the earliest orogenic stages in the Andes, the largest subduction orogen on Earth is fundamental to understanding changes in climate, drainage organization, and biodiversity in South America. Furthermore, it is crucial to unraveling the driving mechani...

3D seismic recognition of deformation elements associated with pulses of growth of the folded belt of the San Jorge Gulf, from early Cretaceous times.

The Cura-Mallín Formation consists of a series of upper Oligocene to Upper Miocene volcanic and sedimentary rocks deposited in continental settings that crop out in the Andean Cordillera in Chile and Argentina between ∼37° and 39°S. Since the 1990s few fossil mammals have been recovered from this unit in the surroundings of Lonquimay, south-central...

The Andes are thought to be formed through discrete contractional stages separated by periods of little to no orogenic construction. This paper analyzes the intervals between the main contractional phases that built the Southern Central Andes between 35° and 37°S in order to determine whether they were characterized by neutral, contractional or ext...

Este es un link de una charla que di sobre este estudio: https://www.facebook.com/segpucpunsaacsc/videos/?ref=page_internal

En el estado de entendimiento actual de los pulsos que han construido los Andes Centrales Australes, se plantean dos fases compresivas acaecidas durante el Cretácico Superior-Eoceno y el Mioceno medio a superior. Estos dos eventos compresivos se vieron interrumpidos entre el Oligoceno y el Mioceno Inferior por una etapa de extensión generalizada en...

actas simposio tectonica andina tucuman 2018. congreso geologico argentino

The origin, extent and timing of intraplate contraction in Patagonia are among the least understood geological processes of southern South America. Particularly, the intraplate Deseado fold-thrust belt (FTB), located in the Patagonian broken foreland (47º-48º30'S), is one of the most enigmatic areas. In this belt, time constraints on tectonic event...

The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic (U-Pb and ⁴⁰Ar/³⁹Ar), provenance, stratigraphic, sedime...

Desertification of Central Patagonia began between ~14–12 Ma and therefore was not directly connected to the opening of the Drake Passage and initial conformation of the Antarctica ice cap in early Miocene times. Local processes, in particular the uplift of the Southern Andes, seem to have played a major role in climatic and biotic changes. We stud...

The study of prehistoric tsunami deposits enables us to appraise the recurrence frequency and improve risk assessments of coastlines. We present a study of tsunami deposits (A.D. 500 to present) exposed at Tirúa, central Chile. Analyses of various proxies such as grain size, petrography, geochemistry, and diatoms were applied to the tsunami deposit...

The most important Cenozoic marine transgression in Patagonia occurred during the late Oligocene–early Miocene when marine waters of Pacific and Atlantic origin flooded most of southern South America including the present Patagonian Andes between ~41° and 47° S. The age, correlation, and tectonic setting of the different marine formations deposited...

Mid-Cenozoic widespread arc magmatism in North Patagonia extends from the forearc to the retroarc zones, representing an anomalous large volume when compared to the present-day arc zone and even other past arc configurations. It represents a crucial stage in Andean arc evolution as was developed after a period of arc waning and within plate magmati...

This book describes the Mesozoic to Cenozoic evolution of the Chilean and Argentinean Andes. The book is structured from a historical perspective concentrating on specific processes explained in each chapter. The chapters cover dynamic subsidence; neotectonics; magmatism; long and short term deformation; spatial development of ancient orogenic proc...

This is the complete geochonological data from our article in 2017 in tectonophysics

Late Cretaceous-early Paleocene magmatism at Southern Central Andes is represented by incomplete and not well-preserved outcrops. A recent U-Pb age from a volcano-sedimentary sequence in the southern Andes of Mendoza province (35°30′S) led to identify Late Mesozoic-Early Cenozoic magmatism, which was not previously registered. We focus on the petro...

Contraction in intraplate areas is still poorly understood relative to similar deformation at plate margins. In order to contribute to its comprehension, we study the Patagonian broken foreland (PBF) in South America whose evolution remains controversial. Time constraints of tectonic events and structural characterization of this belt are limited....

La desertificación de la Patagonia central ocurrió desde ~10 Ma de una manera no directamente conectada con la apertura del Paso Drake y la conformación inicial de la capa de hielo de la Antártida en tiempos del Mioceno temprano, tal como sucedió en otras masas continentales australes. Los procesos locales, en particular el levantamiento de los And...

The Andes extend for ~4,000 km showing remarkable latitudinal differences in height, width, shortening amounts, magmatism and tectonic evolution. A particularly interesting segment along this system is the North Patagonian Andes, since it shows contrasting differences in comparison with the Central Andes to the north including a lower elevation (1–...

The North Patagonian fold-thrust belt (41°–44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new f...

The Chilean margin has been used as the model of an ocean-continent convergent system dominated by compression and active mountain building as a consequence of the strong mechanical coupling between the upper and the lower plates. The Andean Cor-dillera, however, shows evidence of alternating phases of compressional and extensional deformation. Vol...

The Cenozoic tectonic evolution of the North Patagonian Andes is analyzed linking geological and geophysical data in order to decipher the deformational processes that acted through time and relate them to basin formation. Field observations and seismic reflection profiles reveal the shallow structure of the retroarc area where contractional struct...

Resumen The Andean Cordillera shows evidence of alternating phases of compressional and extensional deformation. Volcano-sedimentary marine strata in the Aysén region of southern Chile were investigated to better understand the causes of extensional tectonics and crustal thinning that occurred in the Andean orogeny as these deposits constitute the...

In the last decades, an important amount of studies have dealt with the Patagonian orogen evolution. However, a holistic approach on the evolution of this sector has not been addressed yet. A review of recent advances in different aspects of the Patagonian orogen and its related broken foreland system reveals a close relation between the evolution...

COMMENT Comment on Reply to Comment of Finger et al. (2013) on: 'Evidence for an Early-Middle Miocene age of the Navidad Formation (central Chile): Paleontological, paleoclimatic and tectonic implications' of Gutiérrez et al. (2013, Andean Geology 40 (1): 66-78) In their answer to our Comment (Finger et al., 2013), Le Roux et al. (2013) misundersta...

In this contribution we address the current controversial issues related to the age, correlation, tectonic setting and paleogeographic links of the Cenozoic fossiliferous marine strata that crop out in the eastern sector of the North Patagonian Andes between 41° and 43°S based on new field (detailed geologic and structural mapping), geochronologica...

los estadios y mecánicas deformacionales que afectaron al segmento de transición que va desde los Andes Centrales Australes hasta los Patagónicos Septentrionales. De esta forma surge un cuadro complejo en el cual se alternan segmentos con topografías y amplitudes contrastantes, grados de acortamiento variables, cuencas de antepaís en la región fron...

Upper Cretaceous marine rocks crop out along the Pacific coast of central and south-central Chile between 33 degrees and 37 degrees S. These strata constitute an important reference for the Upper Cretaceous of South America due to their diverse fossil fauna and flora. The type unit of these deposits is the Quiriquina Formation, near Concepcion. Thi...

Marine Cenozoic strata crop out in the western flank of the North Patagonian Andes at Lago Ranco (40°S) and Ayacara (42°S). These deposits, known as the Estratos de Lago Ranco and Ayacara formations, consist of rhythmic successions of sandstone and siltstone. In order to unravel the sedimentary environment, age, and tectonic history of this area du...

The marine gastropod genus Struthiochenopus appears first in the late Cretaceous of the Antarctic Peninsula. Until the Oligocene only one or two species were extant at the same time. This changed drastically in the early Miocene when at least three species were living coevally in southern South America. A possible fourth early Miocene species, Stru...

The Navidad Formation has been the reference unit for the marine Neogene of Chile and the debate about its age and depositional paleoenvironment has a long history. In their recent contribution, Gutierrez et al. present an interpretation of the Navidad Formation that contrasts with that our research group concluded and incorporated in several publi...

The North Patagonian Andes (38°–43°30′S) present topographic and geologic characteristics distinct from those of the Central Andes to the north, including a lower altitude, a predominance of plutonic rocks, and the presence of a major N-S-trending, dextral strike-slip, intra-arc discontinuity known as the Liquiñe-Ofqui Fault Zone (LOFZ). The timing...

Neogene marine strata crop out in the present Coastal Cordillera and Longitudinal Depression of south-central Chile between 38 degrees 30'S and 41 degrees 45'S, indicating the onset of a major marine transgression that covered most of the forearc in this area. In order to determine the sedimentary environment, paleobathymetry, and age of these depo...

The Northern Patagonian Andes have been constructed through multiple mechanisms that range from tectonic inversion of extensional structures of Early to Middle Jurassic age in the Main Andes to Oligocene in the Precordilleran region. These have acted during two distinctive orogenic stages, first in late Early Cretaceous and later in Miocene times L...

The forearc of Central Chile (33°-34°S) is formed by three N-S-trending morphostructural units, including, from west to east, the Coastal Cordillera, the Central Depression, and the Principal Cordillera. The Cenozoic sedimentary rocks that could represent the erosional material generated throughout the morphotectonic evolution of these units accumu...

Palynological assemblages recovered from the Navidad Formation in outcrops of the Cordillera de la Costa, central Chile, are dominated by wood remains, cuticles, spores and pollen grains and fresh water algae (continental elements) with scarce dinoflagellate cysts, acritarchs, foraminiferal linnings marine palynomorphs) indicating that these assemb...

Palynological assemblages recovered from the Navidad Formation in outcrops of the Cordillera de la Costa, central Chile, are dominated by wood remains, cuticles, spores and pollen grains and fresh water algae (continental elements) with scarce dinoflagellate cysts, acritarchs, foraminiferal linnings marine palynomorphs) indicating that these assemb...

Exposures of upper Paleozoic slates of the metamorphic basement near Concepción, central Chile, are covered by transgressive deposits belonging to the Upper Cretaceous Quiriquina Formation. Presence of clusters of the bivalve boring Gastrochaenolites isp. at the irregular and erosive contact between these two units indicates the development of an a...

Deep-marine, Mio-Pliocene strata correlative with the Navidad Formation crop out in different areas along the forearc of south-central Chile (~34°-41°) and have also been recognized in boreholes drilles on the continental shelf. However, at Lago Ranco (40°S) and Ayacara (42°) there are outcrops of marine strata whose age and correlation with these...

Introducción La isla Mocha se sitúa a unos 100 km al suroeste de la península de Arauco ya unos 50 km al oeste de Tirúa (38 30'S, 74 W). Constituye la parte emergida de un bloque alzado de la plataforma continental [1]. Desde el punto de vista estratigráfico [2] señala la presencia de tres sucesiones sedimentarias en la isla Mocha, perteneciente...

New decapod crustacean fossils collected from Eocene rocks of Algarrobo, Chile, have yielded a new genus and species of callianassid, Melipal chilensis. The large sample size makes it possible to recognize marked sexual dimorphism of the major cheliped and pronounced heterochely in the new taxon. Cretaceous fossils from Algarrobo are referred to Pr...

A new Miocene decapod fauna is described from the Navidad Formation of coastal Chile. The fauna includes five callianassoid taxa, none of which is preserved sufficiently to identify to species level. New species include Calappilia? chilensis, Hepatus spininlarginatus, Proterocarcinus navidad, Pilumnus cucaoensis, and Pinnixa navidadensis. A possibl...

Neogene marine strata of the Santo Domingo Formation crop out in the vicinity of Valdivia, south-central Chile (40°S, 73°W). The succession is characterized by dark-gray sandy siltstone with abundant Chondrites isp. The occurrence of this ichnotaxon and lower-bathyal benthic foraminifers is consistent with a slope depositional environment. The abun...

Sedimentological and paleontological studies, including foraminifera, ostracodes, gastropods, and trace fossils, were carried out on Neogene sedimentary successions and offshore boreholes of south-central Chile (∼33°–45°S). Sedimentology shows the occurrence of a thin, shallow marine, basal conglomerate overlain by a succession that includes the fo...

Light and scanning electron microscopic observations on a new species of Adoneis, A. miocenica, from Miocene sediments off the coast of Chile are presented. The new species differs from the only previously described species of Adoneis by having a ring of rimoportulae around the valve in addition to one rimoportula at each apex. Valve shape, velum s...

Publicación ISI Email : kfinger@berkeley.edu A consensus on the biostratigraphic age and depositional environment of the Navidad, Ranquil, and Lacui formations exposed along the tectonic margin of central Chile has been elusive due to conflicting evidence. This study resolves this dilemma and gains further insight regarding the history of the Chile...

Different stratigraphic schemes have been proposed by various authors for the Neogene marine sedimentary deposits cropping out along the central Chilean coast between Valparaíso (~33°00'S) and Punta Topocalma (~34°30'S), without any consensus having been reached. Neither does any agreement exist with respect to the correlation between the deposits...

A buried Holocene marine bed was discovered upon drilling a water well in Algarrobo (33°22'S), located on the coast of central Chile. Radiocarbon dating of a wood fragment found within the deposit indicates an age of 6450 cal yr BP. The top of this bed, 0.25 m-thick, was reached at an elevation of 3.8 m above mean sea level. This bed contains abund...

A buried Holocene marine bed was discovered upon drilling a water well in Algarrobo (33°22′S), located on the coast of central Chile. Radiocarbon dating of a wood fragment found within the deposit indicates an age of 6450 cal yr BP. The top of this bed, 0.25 m-thick, was reached at an elevation of 3.8 m above mean sea level. This bed contains abund...