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... In the following paragraphs, we will refer only to comments that are not self-referenced arguments from authority, v. gr. the contents below the title "Holocene sea level changes in Uruguay", or sentences such as "it has been recognized that Castillos lagoon exhibits the best record to infer Holocene sea level changes.", where the passive voice masks the fact that Bracco's team believe that "Castillos lagoon is the best…", as is demonstrated by the included citations (Bracco et al., 2008;Inda, 2009;Panario and Gutiérrez, 2011;Bracco et al., 2014). Moreover, these references are an abstract, a Master thesis, and two chapters in a local book edited by another member of the team and corresponding author in Bracco et al., 2014). ...
... where the passive voice masks the fact that Bracco's team believe that "Castillos lagoon is the best…", as is demonstrated by the included citations (Bracco et al., 2008;Inda, 2009;Panario and Gutiérrez, 2011;Bracco et al., 2014). Moreover, these references are an abstract, a Master thesis, and two chapters in a local book edited by another member of the team and corresponding author in Bracco et al., 2014). By doing this, we circumscribe to scientific data as stated in the above paragraph. ...
... What we intended was to avoid long-standing nomenclatural problems and to stress factual ones. Bracco et al. (2014) do not counterargue about this, but they only discuss about semantic issues (v. gr. ...
Article
Criticisms of Bracco et al. (2013) about Martínez and Rojas (2013) are commented. We still claim that the sea level curve shown in the latter paper is the first statistically, testable curve produced for Uruguay. Previous attemps were made by hand. With the exception of some typographical errors correctly signaled by Bracco et al. (2013), it is demontrasted that their assumptions about our work are wrong and subjective.
... The Atlantic coast of Uruguay did not experience submergence or uplift tectonic processes during the Holocene (Isla and Angulo 2016) which means that sea level change was the main driver of coastal dynamics and evolution. Regional research efforts developed in Uruguay, SE Brazil, and Argentina (Angulo et al. 2006;Bracco et al. 2014;Cavallotto et al. 2004;Isla 1989;Martin and Suguio 1992;Martínez and Rojas 2013) showed remarkable agreement about inferred sea level curves for this part of South America. These findings, coupled with intensive topographic surveys and paleolimnological multiproxy analyses through several coastal lagoon bottoms, wetlands, landforms, and exposed coastal paleosurfaces, allowed the reconstruction of past regional climate and coastal evolution and to generate the most likely coastal configurations Inda et al. 2017) for the recently defined Holocene stages (Walker et al. 2018). ...
... ka BP, sea level reached current stands. Sea level continued the rising trend until it reached around 4.5-5 m above current sea level around 5.5 ka BP, an event referred as the Maximum Holocene Transgression (MTH hereafter; Bracco et al. 2014;Martínez and Rojas 2013;Inda et al. 2006b). During this period, the sea submerged a wide array of former terra firme landscapes that were sculpted during the Pleistocene (the Dolores and Libertad formations; Ubilla and Martínez 2016). ...
... Paleoenvironmental scenarios for the Holocene stages were reconstructed from available literature on the topic for the study area , . Inferences about most likely coastal configuration for these ages were based on local sea level curves (Bracco et al. 2014;Martínez and Rojas 2013), landform chronologies (Inda et al. 2017;Panario and Gutiérrez 1999), topographic and bathymetric information. ...
Book
This book introduces selected contributions from the GEGAL (Spanish acronym for Latin American Geoarchaeological Studies Group) Workshop held at La Paloma Beach, Uruguay, with a focus on Coastal Geoarchaeology, and an attendance of more than 50 researchers, students and professionals from several Latin American countries. The contributions were selected in order to encompass the vast array of environmental, geomorphological and archaeological contexts comprised in the geographical frame of Latin America. Topics covered through the chapters include specific issues such as human occupation and fluvial dynamic processes in mountain and lowland environments, methodological developments in dating methods, taphonomy and chemical proxies, as well as landscape modification by anthropogenic disturbances. As the first compilation of Coastal Geoarchaeology for Latin America, this book is intended to become a useful tool for students, researchers and professionals from related fields, as it comprises not only the regional state of the art, but also new insights and developments which can be potentially applied to other contexts world wide.
... 6.0 ka; since then, a regressive sea-level trend has been apparent. Within this general trend, a minor transgressive event was identified at 2.5 ka (3 m above mean sea level) and then the regressive phase continued until it reached current sea level around 1.0 ka (Bracco et al., , 2014. We note that tectonic processes, such as the submergence and/or uplift of the coastline, played no role in these sea-level changes (Isla & Angulo, 2016). ...
... These landforms were formed above and below the average water level: erosion terraces, tidal plains, barrier systems, beach ridges, and littoral deposits. Most contain bivalve shell remains that allowed for the development of radiocarbon chronologies (Fig. 5;Bracco et al., 2011Bracco et al., , 2014. ...
... Together with littoral landforms, geochronological and biological prox- ing Holocene sea levels, and this comprehensive data set represented the starting point for developing the Uruguayan coast sea-level curve (Bracco et al., , 2014. ...
Article
Paleoenvironmental reconstructions coupled with archaeological research are useful tools for discriminating natural versus anthropogenic environmental variability and identifying local environmental responses to global changes and consequent human adaptations. Here we present a multidisciplinary study focused on the identification of drivers and mechanisms that shaped environments along the Uruguay coast and how those environments influenced prehistoric settlement patterns, subsistence strategies, and site formation processes at the archaeological sites of Cape Polonio and Castillos Lagoon. We identify a strong linkage between environmental dynamics and the timing, spatial allocation, and subsistence strategies of prehistoric inhabitants. Human occupation took place in very specific landscape settings where contemporaneous settlements were identified in persistent eolian landscape features. An opportunistic exploitation of more dynamic locations was also identified, where sea-level shifts created land surfaces preferred by humans. The results of our study represent a useful tool not only for identifying archaeological sites in similar contexts but also for providing insights into how modern coastal populations might adapt to changing environments associated with rising sea level.
... The Castillos Lagoon became the focus of research related to Holocene sea level changes within the system of coastal lagoons in Uruguay due to its well-preserved record, including a high number of geomorphological, stratigraphic, and geoarchaeological structures. From it, focusing on the altimetry and 14 C chronologies of the Bracco et al. (2014) geoforms found in its coasts, the first curves of relative sea level for Uruguay were developed (Bracco and Ures 1998;Bracco et al. 2011b;Bracco et al. 2014) (Fig. 2). Although this meant significant progress in determining the trend of sea level behavior in this area, these models are based mainly on two assumptions that limit their validity in order to achieve a greater altimetric and temporal resolution. ...
... The Castillos Lagoon became the focus of research related to Holocene sea level changes within the system of coastal lagoons in Uruguay due to its well-preserved record, including a high number of geomorphological, stratigraphic, and geoarchaeological structures. From it, focusing on the altimetry and 14 C chronologies of the Bracco et al. (2014) geoforms found in its coasts, the first curves of relative sea level for Uruguay were developed (Bracco and Ures 1998;Bracco et al. 2011b;Bracco et al. 2014) (Fig. 2). Although this meant significant progress in determining the trend of sea level behavior in this area, these models are based mainly on two assumptions that limit their validity in order to achieve a greater altimetric and temporal resolution. ...
... BP (2σ): 5331-5374 (p = 0.045) and 5459-5715 (p = 0.995), and 4740 ± 50 14 C yr BP (Cal. BP (2σ): 5316-5487 (p = 0.754) and 5506-5582 (p = 0.246) (Bracco et al. 2014). The calibration of the conventional radiocarbon ages was obtained using ShCal13 curve for the Southern Hemisphere (Hogg et al. 2013). ...
... The Atlantic coast of Uruguay did not experience submergence or uplift tectonic processes during the Holocene (Isla and Angulo 2016) which means that sea level change was the main driver of coastal dynamics and evolution. Regional research efforts developed in Uruguay, SE Brazil, and Argentina (Angulo et al. 2006;Bracco et al. 2014;Cavallotto et al. 2004;Isla 1989;Martin and Suguio 1992;Martínez and Rojas 2013) showed remarkable agreement about inferred sea level curves for this part of South America. These findings, coupled with intensive topographic surveys and paleolimnological multiproxy analyses through several coastal lagoon bottoms, wetlands, landforms, and exposed coastal paleosurfaces, allowed the reconstruction of past regional climate and coastal evolution and to generate the most likely coastal configurations Inda et al. 2017) for the recently defined Holocene stages (Walker et al. 2018). ...
... ka BP, sea level reached current stands. Sea level continued the rising trend until it reached around 4.5-5 m above current sea level around 5.5 ka BP, an event referred as the Maximum Holocene Transgression (MTH hereafter; Bracco et al. 2014;Martínez and Rojas 2013;Inda et al. 2006b). During this period, the sea submerged a wide array of former terra firme landscapes that were sculpted during the Pleistocene (the Dolores and Libertad formations; Ubilla and Martínez 2016). ...
... Paleoenvironmental scenarios for the Holocene stages were reconstructed from available literature on the topic for the study area , ). Inferences about most likely coastal configuration for these ages were based on local sea level curves (Bracco et al. 2014;Martínez and Rojas 2013), landform chronologies (Inda et al. 2017;Panario and Gutiérrez 1999), topographic and bathymetric information. ...
... The Atlantic coast of Uruguay did not experience submergence or uplift tectonic processes during the Holocene (Isla and Angulo 2016) which means that sea level change was the main driver of coastal dynamics and evolution. Regional research efforts developed in Uruguay, SE Brazil, and Argentina (Angulo et al. 2006;Bracco et al. 2014;Cavallotto et al. 2004;Isla 1989;Martin and Suguio 1992;Martínez and Rojas 2013) showed remarkable agreement about inferred sea level curves for this part of South America. These findings, coupled with intensive topographic surveys and paleolimnological multiproxy analyses through several coastal lagoon bottoms, wetlands, landforms, and exposed coastal paleosurfaces, allowed the reconstruction of past regional climate and coastal evolution and to generate the most likely coastal configurations (del Puerto et al. 2013;Inda et al. 2017) for the recently defined Holocene stages (Walker et al. 2018). ...
... ka BP, sea level reached current stands. Sea level continued the rising trend until it reached around 4.5-5 m above current sea level around 5.5 ka BP, an event referred as the Maximum Holocene Transgression (MTH hereafter; Bracco et al. 2014;Martínez and Rojas 2013;Inda et al. 2006b). During this period, the sea submerged a wide array of former terra firme landscapes that were sculpted during the Pleistocene (the Dolores and Libertad formations; Ubilla and Martínez 2016). ...
... Paleoenvironmental scenarios for the Holocene stages were reconstructed from available literature on the topic for the study area Inda et al. 2011, . Inferences about most likely coastal configuration for these ages were based on local sea level curves (Bracco et al. 2014;Martínez and Rojas 2013), landform chronologies Panario and Gutiérrez 1999), topographic and bathymetric information. ...
Chapter
Coastal geoarchaeology has the potential to transform itself in a leading discipline with the capability to provide useful insights for the adaptation of coastal populations to rising seas and changing environments in a future that is getting alarmingly closer. In this contribution, we present the results of a research that combined the state of the art for Uruguayan coastal archaeology with Holocene paleoenvironmental evolution and modern anthropogenic impact from a basin-wide perspective. Our findings identified a direct relationship between sea level evolution and climate dynamics with the scarcity of human evidences for the Greenlandian and Northgrippian stages in coastal environments, where harsher environmental conditions could have discouraged the exploitation of these landscapes but also erased these earlier evidences after sites abandonment. The prolific archaeological record for the Meghalayan was explained by the establishment of more favorable climatic conditions and relatively stable environments promoting the spread and settlement across coastal landscapes. Despite this fact, modern anthropogenic impact poses a growing threat to this cultural heritage, as market-driven real estate development over capes and dune fields and cropland expansion over grasslands are occupying critical areas. In this scenario, this work identified less impacted areas where exhaustive archaeological surveys coupled with other conservation measures are urgently needed.
... The Atlantic coast of Uruguay did not experience submergence or uplift tectonic processes during the Holocene (Isla and Angulo 2016) which means that sea level change was the main driver of coastal dynamics and evolution. Regional research efforts developed in Uruguay, SE Brazil, and Argentina (Angulo et al. 2006;Bracco et al. 2014;Cavallotto et al. 2004;Isla 1989;Martin and Suguio 1992;Martínez and Rojas 2013) showed remarkable agreement about inferred sea level curves for this part of South America. These findings, coupled with intensive topographic surveys and paleolimnological multiproxy analyses through several coastal lagoon bottoms, wetlands, landforms, and exposed coastal paleosurfaces, allowed the reconstruction of past regional climate and coastal evolution and to generate the most likely coastal configurations Inda et al. 2017) for the recently defined Holocene stages (Walker et al. 2018). ...
... ka BP, sea level reached current stands. Sea level continued the rising trend until it reached around 4.5-5 m above current sea level around 5.5 ka BP, an event referred as the Maximum Holocene Transgression (MTH hereafter; Bracco et al. 2014;Martínez and Rojas 2013;Inda et al. 2006b). During this period, the sea submerged a wide array of former terra firme landscapes that were sculpted during the Pleistocene (the Dolores and Libertad formations; Ubilla and Martínez 2016). ...
... Paleoenvironmental scenarios for the Holocene stages were reconstructed from available literature on the topic for the study area , . Inferences about most likely coastal configuration for these ages were based on local sea level curves (Bracco et al. 2014;Martínez and Rojas 2013), landform chronologies (Inda et al. 2017;Panario and Gutiérrez 1999), topographic and bathymetric information. ...
... Holocene sea-level history has been reconstructed for different areas of Buenos Aires province (e.g. Isla, 1989;Aguirre and Whatley, 1995;Cavallotto et al., 1995;G omez and Perillo, 1995;Isla and Espinosa, 1998;G omez et al., 2006) and Uruguay (Bracco et al., 2011(Bracco et al., , 2014Rojas, 2013, 2014). With the exception of the work by G omez et al. (2006) and Bracco et al. (2011) who have indicated a negative relative sea-level (RSL) oscillation around 2650 14 C yr BP in Bahía Blanca estuary (Fig. 1) and a negative short-term oscillation at c. 4500 cal yr BP for the Uruguayan coast ( Fig. 2) respectively, other publications have proposed a simple regressive trend to the present position after the emplacement of a maximum Holocene highstand. ...
... It shows rising sea-levels following the Last Glacial Termination (LGT), reaching a RSL maximum of þ6.5 m above present at c. 6500 cal yr BP, followed by a stepped regressive trend towards the present (Fig. 2a). On the other hand, Holocene RSL curves for the Uruguayan coast that include data from both the northeastern RDP and the Atlantic coast have been reconstructed by Bracco et al. (2011Bracco et al. ( , 2014 and Rojas (2013, 2014). These curves show some discrepancies concerning the timing and magnitude of the mid-Holocene highstand and the regressive trend (Fig. 2b). ...
Article
Full-text available
This study critically reviews the relative sea-level (RSL) data from the Río de la Plata (RDP) (Argentina and Uruguay) in order to analyze the Holocene RSL changes in this region and thus capture the general trend illustrated by both the data and the high-degree polynomial regression analyses which show good agreement with the ICE-6G_C (VM6) model. The previously inferred Holocene sea-level histories reconstructed from palynological and diatom records from the northern and the southern RDP are also compared to the RSL curves proposed in this work. Analysis of the RSL database revealed that the RSL rose to reach the present level at or before c. 7000 cal yr BP, with the peak of the sea-level highstand c. +4 m between c. 6000 and 5500 cal yr BP (depending on the statistical method used) or at c. 7000 cal yr BP according to the ICE-6G model prediction, gradually falling after this time to the present position. The subaerial data tell a consistent story for the last 6000 years for the RDP but the subsurface data are not in agreement with these data or with the glacial isostatic adjustment (GIA) predictions. Since much of the subaerial data come from shells on beaches, beach ridges and storm beaches, they cannot be strictly interpreted as RSL index points. It seems likely that the predicted curves are somewhat high and could be overestimated. The “smooth” model of the late Holocene sea-level decline is in close agreement with both the GIA model predictions and the reconstruction of RSL from palynological and diatom records. The models provide no evidence to suggest that there has been a significant trend of change in the speed of sea-level fall or oscillations during the falling stage system tract. The non-parametric regression model, the GIA predictions and the trend inferred by palynological and diatom data trace out a slow sea-level fall for the last c. 6000 cal yr BP. We critically assessed published Holocene sea-level data from the RDP to produce a Holocene RSL curve of sufficient quality to provide a location in this area for testing theoretical models for the Atlantic coast of South America.
... First, we did random test regarding the spatial distribution of the shell middens (sites). A nearest neighbour index analysis (Clark and Evans 1954;Krebs 1999) was done, in order to know if the shell middens are distributed by chance, in a uniform or disperse way or in an aggregate one. Then, we analyzed the probable causes of the distribution through the study of the available resources (Hodder and Orton 1990). ...
... The sample rarefaction procedure (Mao tau) (Colwell et al. 2004) was applied to a matrix of presence-absence data from Table 6.2, to estimate species richness as a function of number of samples. Also we applied individual rarefaction procedure (Krebs 1999) (from NMI data in Table 6.2) to estimate the number of classes or taxa in samples having unequal frequencies which can then be compared with each other at the same level. The small mollusk Heleobia sp. was excluded in this last analysis because the abundance masks the rest of the species. ...
Chapter
Full-text available
Settlement patterns of the shell middens from the middle-late Holocene of the Santa Lucía basin (left margin of the Río de la Plata), are analyzed concerning the natural resources that they reveal. Spatial relationships among the shell middens and the environment are characterized by means of nearest neighbour index analysis and by correspondence analysis. The faunistic resources identified in the shell middens are analyzed regarding their predictability, potential distribution, density, and seasonality. It is concluded that the shell middens tend to be dispersed, and the importance of the faunistic resources is evaluated in shaping this distribution. Most of the faunistic resources recovered in the middens may proceed from around 3 to 5 km, and are potentially dense, predictable, and available along the year. These results are integrated with the knowledge of the organization of space in societies from 3000 years BP, with early presence of cultigens and ceramic production, reduced residential mobility, and adapted to the changes and transformations of the coastal environments.
... Los cambios del nivel del mar son parte de las interacciones entre la atmosfera, los océanos, los casquetes polares y la tierra sólida. Durante las últimas tres décadas, se publicaron muchas evidencias sobre los cambios del nivel del mar en la costa del SESA (Isla, 1989;Martin y Suguio, 1992;Angulo y Lessa, 1997;Isla, 1989;Angulo et al., 1999;Lessa et al., 2000;Bezerra et al., 2003;Martin et al., 2003;Cavallotto et al., 2004;Angulo et al., 2006;Gyllencreutz et al., 2010;Martínez y Rojas 2013;Bracco et al., 2014). A pesar de algunas diferencias en estas reconstrucciones, todas ellas postulan que luego del rápido incremento del nivel del mar asociado a la desglaciación, se alcanzo el máximo nivel del mar entre 6000 y 5200 a AP (Fig. 3). ...
... Para la costa uruguaya, Bracco et al. (2014) propusieron una rápida caída del nivel del mar para los 4300 a AP, mientras que Martínez y Rojas (2013) propusieron una caída del nivel del mar constante después del 6000 a AP. Para la costa de Brasil, dos eventos rápidos de sumersión/emersión fueron postulados para los 4000-3900 y 2800-2700 a AP (Martin y Suguio, 1993), pero otros autores no están de acuerdo con la ocurrencia de dichos eventos (Angulo et al., 2003). ...
Chapter
Full-text available
Este artículo introductorio describe al sistema oceanográfico y sedimentario de Uruguay, con el objetivo de presentar una revisión corta de los trabajos realizados recientemente. El análisis de un conjunto de testigos tomados recientemente en la plataforma continental y talud uruguayo permitió inferir cómo estas zonas ambientales están conectadas entre sí. El depocentro marino más proximal está localizado en un paleo-valle sepultado por el Río de la Plata (RdlP), a 20 km de la costa uruguaya. Un testigo de sedimento de 10 m de longitud que abarca los últimos 1200 años, indica una influencia directa de la descarga del RdlP y de los patrones de viento prevalecientes, según se dedujo de los patrones de sedimentación y los cambios históricos de la salinidad. Los cambios ambientales inferidos a partir del registro de diatomeas y datos geoquímicos, están asociados tanto a los cambios naturales como antropogénicos a partir de la década del 60. Los depocentros están distribuidos en toda la plataforma continental y contienen información principalmente asociada a la trangresión del Holoceno, cuando el creciente nivel del mar forzó al sistema paleo-costero a retroceder rápidamente. Hasta el comienzo del Holoceno, el paleo-valle del RdlP fue la mayor vía de drenaje de las descargas fluviales, proveyendo la mayor parte del material terrígeno al cono de Río Grande del Sur (Brasil). Un depocentro excepcional está localizado justo al lado del borde de la plataforma. Allí, los cambios latitudinales del frente hidrográfico de la plataforma están registrados en detalle para todo el Holoceno, y sugieren que este frente fue raramente estable durante este período. De esta forma, resulta obvio que la dinámica de transporte de este frente junto a fuertes tormentas ejercen control en la movilización y exportación de material desde la plataforma hacia el talud. Este capítulo muestra el gran valor de los registros de los depocentros marinos (los cuales pueden hallarse incluso en plataformas dominadas por corrientes), para descifrar los cambios ambientales pasados y el contraste entre las condiciones pre-industriales e industriales. Futuros estudios deberían enfocarse especialmente en los impactos antropogénicos y en la interacción de los sistemas oceanográfico, ecológico y sedimentario de la plataforma continental, ya que este patrimonio marino está muy poco estudiado en el Uruguay, se necesita mayor conocimiento del mismo, y está casi sin protección hasta la fecha.
... Los cambios del nivel del mar son parte de las interacciones entre la atmosfera, los océanos, los casquetes polares y la tierra sólida. Durante las últimas tres décadas, se publicaron muchas evidencias sobre los cambios del nivel del mar en la costa del SESA (Isla, 1989;Martin y Suguio, 1992;Angulo y Lessa, 1997;Isla, 1989;Angulo et al., 1999;Lessa et al., 2000;Bezerra et al., 2003;Martin et al., 2003;Cavallotto et al., 2004;Angulo et al., 2006;Gyllencreutz et al., 2010;Martínez y Rojas 2013;Bracco et al., 2014). A pesar de algunas diferencias en estas reconstrucciones, todas ellas postulan que luego del rápido incremento del nivel del mar asociado a la desglaciación, se alcanzo el máximo nivel del mar entre 6000 y 5200 a AP (Fig. 3). ...
... Para la costa uruguaya, Bracco et al. (2014) propusieron una rápida caída del nivel del mar para los 4300 a AP, mientras que Martínez y Rojas (2013) propusieron una caída del nivel del mar constante después del 6000 a AP. Para la costa de Brasil, dos eventos rápidos de sumersión/emersión fueron Figura 3. Posición de la línea de costa uruguaya para a) nivel del mar actual y b) para el máximo nivel del Holoceno para los 5200 a AP (fuente: Inda et al., 2011). ...
Conference Paper
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The continental margin off SE South America hosts one of the world’s most energetic hydrodynamic regimes but also the second largest drainage system of the continent. Both, the ocean current system as well as the fluvial runoff are strongly controlled by the atmospheric circulation modes over the region. The distribution pattern of particular types of sediments on shelf and slope and the long-term built-up of depositional elements within the overall margin architecture are, thus, the product of both, seasonal to millennial variability as well as long-term environmental trends. This talk presents how the combination of different methodological approaches can be used to obtain a comprehensive picture of the variability of a shelf and upper-slope hydrodynamic system during Holocene times. The particular methods applied are: (a) Margin-wide stratigraphic information to elucidate the role of sea level for the oceanographic and sedimentary systems since the last glacial maximum; (b) Palaeoceanographic sediment proxies combined with palaeo-temperature indicating isotopes of bivalve shells to trace lateral shifts in the coastal oceanography (particularly of the shelf front) during the Holocene; (c) Neodymium isotopes to identify the shelf sediment transport routes resulting from the current regime; (d) Sedimentological/geochemical data to show the efficient mechanism of sand export from the shelf to the open ocean; (e) Diatom assemblages and sediment element distributions indicating palaeo-salinity and the changing marine influence to illustrate the Plata runoff history. Sea level has not only controlled the overall configuration of the shelf but also the position of the main sediment routes from the continent towards the ocean. The shelf front has shifted frequently since the last glacial times probably resulting from both, changes in the Westerly Winds intensity and in the shelf width itself. Remarkable is a southward shift of this front during the past two centuries possibly related to anthropogenic influences on the atmosphere. The oceanographic regime with its prominent hydrographic boundaries led to a clear separation of sedimentary provinces since shelf drowning. It is especially the shelf front which enhances shelf sediment export through a continuous high sand supply to the uppermost slope. Finally, the Plata River does not continuously provide sediment to the shelf but shows significant climate-related changes in discharge during the past centuries. Starting from these findings, three major fields of research should, in general, be further developed in future: (i) The immediate interaction of the hydrodynamic and sedimentary systems to close the gaps between deposit information and modern oceanographic dynamics; (ii) Material budget calculations for the marginal ocean system in terms of material fluxes, storage/retention capacities, and critical thresholds; (iii) The role of human activity on the atmospheric, oceanographic and solid material systems to unravel natural vs. anthropogenic effects and feedback mechanisms.
... The local phytolith records from these coastal lagoons that were likely connected to the Atlantic Ocean during the mid-Holocene cannot be used to infer the environmental conditions for the Merin Lagoon basin during the mid-Holocene. Instead these data should be used to resolve the controversy about the timing and nature of the relative sea-level during the Late Holocene in Uruguay (BRACCO et al. 2014;MARTÍNEZ and ROJAS 2013). From the above discussion, it become clear that Bracco et al. (2005Bracco et al. ( , 2011) conclusions about regional landscapes derived from the phytolith records of these coastal lagoons should be revised. ...
... yr BP. However, this data is contested by (BRACCO et al. 2014). In southern Brazil, Angulo et al. (2006), claim that the sea level has been above that of the present and has been smoothly declining since the last ca. ...
Article
Full-text available
In this article, we focus on three case studies, which show how the climatic fluctuations that took place during the mid and late Holocene had a major impact on the native groups that inhabited the La Plata Basin region. First, we summarized the archaeological and the paleoenvironmental records of the mid-Holocene related to the emergence of “Constructores de Cerritos” in south-eastern Uruguay. Then, we review the evidence for a late Holocene more intense occupation of the southern Brazilian Highlands by the southern proto-Jê groups and its association to the expansion of mixed Araucaria forest in this region. After that, we review the evidence for sea-level fluctuations and changes in settlement patterns of the mid and late-Holocene Sambaqui people that lived along the Atlantic coast of south-eastern Brazil. Finally, we briefly discuss the implications of these environmental changes for the development and dynamics of these cultures in the La Plata Basin region.
... The complexity between sea level regression and transgression during this ~4.2 ka is reported from various researches (Berkelhammer et al., 2012;Cullen et al., 2000;Dixit et al., 2014;Sharma et al., 2020;Bracco et al., 2014) (Fig. 10). In that context, this study helps to generate the regional sea level. ...
... Comparison of climate proxies with sea level changes based on various studies across the globe. (a) Isotopic record from NE India (Berkelhammer et al., 2012) (b) and (c) aeolian dolomite and CaCO 3 percentage in an ocean core, Gulf of Oman (Cullen et al., 2000) (d) δ 18 O of Melanoides gastropod from Kotla Dahar lake, Rajasthan (Dixit et al., 2014) (e) Relative Sea level changes in Gulf of Kachchh (modified after Sharma et al., 2020) (f) Relative Sea level curve from Maldives(Mörner et al., 2004) (g) The sea level variation change curve inferred from Lagoon Castillos records(Bracco et al., 2014). ...
Article
The present study focuses on the mechanism, climate, and sea-level implications of the coastal dune building activity in the eastern coast of Kori Creek (Gulf of Kachchh). Around 10 m thick dune is investigated using sedimentology, geochemistry, and optical chronology. This study suggests that the dune sediment that overlies the Tertiary Oyster Bed is dated to ~4 ka. The grain size analysis and correlation of textural parameters of the inland dunes and coastal dunes showed no stark difference, revealing they were deposited during the same time. Further, the geochemical data generated from the samples of the coastal dune site represent semi-arid to semihumid climate with increasing chemical maturity and weakening monsoon during the time of deposition. Based on the current erosion dune face and optical ages of the samples, it can be related that the Kachchh coastline was exposed due to the lowering of the sea level at the time of the deposition of coastal dunes. The sea must be at a lower level to attain a preferable condition for the deposition of dunal landforms. The lowering of the sea exposed the beach with sandy material, which got blown away in strong wind, leading to dunes deposition. The cold phase at ~4.2ka became the most conducive environment of coastal dune formation.
... The sedimentary sequence started circa 6100 yr BP, a period defined by the Maximum Holocene Transgression (MHT) developed in the region from 6500 yr BP to 5500 yr BP (Angulo et al., 2006;Bracco et al., 2014Bracco et al., , 2011Cavallotto et al. 2004;Inda, 2009;Isla, 1989;Martin and Suguio, 1992;Tomazelli, 1990). In this scenario, with a sea level almost 6 m amsl, the area occupied today by the lagoon and the southern portion of the watershed set was what Kjerfve (1994) described as a bay: a coastal indentation, resulting in this case from geological processes, strongly affected by sea level fluctuations and tides (Fig. 7). ...
Article
Coastal lagoons across the globe are increasingly experiencing undesired and sudden changes caused by human disturbances. Nevertheless, little is known about how long-term natural dynamics and anthropogenic impacts interact to drive the systems to their current state. This study discriminated natural- and human-induced changes in a shallow coastal lagoon near Punta del Este, Uruguay, using a multidisciplinary approach. The genesis of the water body resulted from a Middle Holocene marine transgression circa 6000yr cal BP. From this time to about 4400 yr cal BP, a comprehensive set of proxies revealed a highly variable scenario, with alternating lagoon states linked to climatic variability. A Late Holocene hiatus was also identified in the sediment profile, linked to the barrier and inlet formation that caused a predominance of erosion over net deposition. Results showed that anthropogenic disturbances modified the landscape substantially and shifted the entire watershed to a previously unknown and undesired state. A freeway constructed in 1955 AD subsequently closed the lagoon's natural inlet and transformed the coastal water body into an artificial reservoir. After such significant human impact, the lagoon experienced a sharp decrease in water surface area along with an intensification of the siltation/eutrophication processes, as inferred from multiproxy data. Findings of this study are useful to identify early signals of human disturbances in pristine or less impacted coastal systems to assist mitigation measures and/or restoration actions.
... Bracco-Boksar et al. (2011), combining evidence with varying reliability, and not adjusting for the height of the deposition, constructed by hand a curve based on the deposits around the current Rocha Lagoon, and concluded that the maximum Holocene sea level was reached approximately 6,000 years ago, and that since then there has been a fluctuating declining trend. According to Martínez and Rojas (2013), who statistically used data from old berm deposits corrected for the height of the deposition, the maximum sea level (around 3 m above the present sea level) was reached also around 6,000 years ago, but that after that there was a smooth lowering of the sea level ( Fig. 2.14) (see also Bracco et al. 2014;Martínez and Rojas 2014;Mourelle et al. 2015). According to numerical ages, arranged in updated tables, correlation with the Marine Isotope Stage 3 (MIS-3) and MIS-2 is discussed for southern and northern Late Pleistocene beds. ...
Book
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This book provides an updated review and criticism of the progress of the continental, transitional and marine Quaternary deposits of Uruguay. It is primarily based on an analysis of the geological and paleontological evidences, synthesizing the time (numerical ages, biostratigraphy), environment and climatic situations involved and highlighting the most relevant paleontological content.
... However, the exact dates for these fluctuations and their amplitude are subjects of debate. Current data by Martínez and Rojas (2013) indicate that present-day sea level was reached in Uruguay by around 6000 cal yr BP and that there was a major marine high stand, attaining 3.75 m on average, at around 5000 cal yr BP. Bracco et al. (2014), however, contest these data. In southern Brazil, Angulo et al. (2006) claim that sea level has been above that of the present and has been gradually declining over the last 5000-5800 cal yr BP, with a maximum height of no more than 4 m. ...
Article
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Newly created academic programs at Brazilian universities have provided the impetus for new archaeological projects in southeastern South America during the last two decades. The new data are changing our views on emergent social complexity, natural and human-induced transformation of the landscape, and transcontinental expansions and cultural interactions across the Río de la Plata basin during the Middle and Late Holocene. We concentrate on six major archaeological traditions/regions: the Sambaquis, the Pantanal, the Constructores de Cerritos, the Tupiguarani, the Southern Proto-Jê, and the middle and lower Paraná River. Diverse and autonomous complex developments exhibit distinct built landscapes in a region previously thought of as marginal compared with cultural developments in the Andes or Mesoamerica. The trajectories toward increased sociopolitical complexity flourished in very different and changing environmental conditions. While some groups were pushed to wetland areas during a drier mid-Holocene, others took advantage of the more humid Late Holocene climate to intensively manage Araucaria forests. The start of the second millennium AD was a critical period marked by an increased number of archaeological sites, the construction of ceremonial architecture, and the intensification of landscape transformation; it also was marked by the rapid expansion of influences from outside the La Plata basin. The Amazonian Tupiguarani and Arawak newcomers brought with them significant changes in technologies and social and political structures, as well as novel landscape management practices.
... Almost all scientific references regarding RSL developed on the east coast of South America reveal a sea-level higher than MSL at around 5000 yrs BP (Martin and Suguio, 1975;Suguio et al., 1976Suguio et al., , 1985Martin et al., 1979Martin et al., , 1998Angulo and Lessa, 1997;Isla, 1998;Bezerra et al., 2003;Cavallotto et al., 2004;Angulo et al., 2006;Martínez and Rojas, 2013;Bracco et al., 2014;Cunha et al., 2017;Prieto et al., 2017;Castro et al., 2018;Tâmega et al., 2019). According to , between 5500 and 4500 cal yrs BP, RSL has reached the first Holocene peak with a maximum height of 2.5 m above MSL, the last maximum peak of the Holocene transgression in southeastern Brazil, which the authors named as "the Cabo Frio Transgression". ...
Article
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O presente trabalho consiste no estudo da mecânica do transporte de sedimentos em suspensao no estuario do rio Macuse em Mocambique, costa sudeste Africana. Os procedimentos metodologicos basearam-se em levantamentos geomorfologicos e oceanograficos definidos em 42 estacoes devidamente georreferenciadas. Realizou-se medicoes de correntes de mares in situ atraves de correntometro e maregrafo-RBRduo, fixos na estacao do porto de Macuse. O trabalho de campo compreendeu dois periodos: o periodo de 17 a 19 de novembro de 2013 e 16 a 21 de novembro de 2014. Os sedimentos em suspensao foram coletados com garrafa de Naskin especifica para a coleta de sedimentos na lȃmina de agua. Os sedimentos foram filtrados a partir de um papel de fibra de 47µm numa bomba de vacuo, e medidos numa balanca eletronica. Conduziu-se uma simulacao hidrodinâmica atraves de um modelo tridimensional ELCOM-CAEDYM entre novembro de 2013 e novembro de 2014. A calibracao e validacao dos resultados simulados foram realizadas por meio de uma comparacao com os dados coletados em campo. Os resultados indicam que os sedimentos em suspensao no estuario do rio Macuse sao dependentes das correntes geradas por mares sob efeito da circulacao hidrodinâmica ciclica e do tamanho de sedimentos transportados. As concentracoes dos sedimentos simulados sugerem a ocorrencia de assoreamento por fracoes muito finas variando entre silte e areia muito fina na escala de wenthworth, associada as zonas de fluxo inferior a 0,1m s -1 . A aplicacao do modelo ELCOM-CAEDYM mostrou um desempenho satisfatorio na producao de resultados da concentracao de sedimentos suspensos que variaram entre ~100 g l -1 e ~300 g l -1 nos periodos de mares enchentes e vazantes. O desempenho satisfatorio do modelo mostrou suas adequabilidades e robustez na predicao de futuros cenarios da mecânica de transporte envolvendo processos geologicos, geomorfologicos e oceanograficos no estuario de Macuse e no mundo.
... Almost all scientific references regarding RSL developed on the east coast of South America reveal a sea-level higher than MSL at around 5000 yrs BP (Martin and Suguio, 1975;Suguio et al., 1976Suguio et al., , 1985Martin et al., 1979Martin et al., , 1998Angulo and Lessa, 1997;Isla, 1998;Bezerra et al., 2003;Cavallotto et al., 2004;Angulo et al., 2006;Martínez and Rojas, 2013;Bracco et al., 2014;Cunha et al., 2017;Prieto et al., 2017;Castro et al., 2018;Tâmega et al., 2019). According to , between 5500 and 4500 cal yrs BP, RSL has reached the first Holocene peak with a maximum height of 2.5 m above MSL, the last maximum peak of the Holocene transgression in southeastern Brazil, which the authors named as "the Cabo Frio Transgression". ...
Article
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A review of relative sea-level (RSL) oscillations during the Holocene in Rio de Janeiro, southeastern Brazil, is presented based on new data. This new data encompasses analytical techniques, altimetric corrections and age recalibrations, using the marine local radiocarbon reservoir correction of 96 ± 48 yrs. The effectiveness of geological and biological RSL indicators was tested, aiming to provide consistent information for future researches on the east coast of South America. Results confirm that RSL during Late Pleistocene - Holocene transition (11,970–11,122 cal yrs BP) was 4.5 m below Mean Sea-level (MSL). After that transition, a relatively rapid rise began. At approximately 7948–7598 cal yrs BP, the MSL was 0.5 m below the current marine level. Present-day, “zero”, was reached for the first time in the Holocene, at approximately 7686–7269 cal yrs BP. The maximum level of the Holocene marine transgression occurred around 4787 - 4104 cal yrs BP with a height of 3.0 m above MSL. At the point of maximum transgression, the sea-level began a general behavior of lowering. However, between 3981 and 3345 to 1852 - 1413 cal yrs BP, evidence from vermetids suggests several alternating periods of slow and rapid sea-level, identified by four oscillations. New records, between 1220 - 780 and 1055 - 665 cal yrs BP, have indicated a continue lowering trend of RSL.
... The sample rarefaction procedure (Mao tau) (Colwell et al. 2004) was applied to a matrix of presence-absence data from Table 6.2, to estimate species richness as a function of number of samples. Also we applied individual rarefaction procedure (Krebs 1999) (from NMI data in Table 6.2) to estimate the number of classes or taxa in samples having unequal frequencies which can then be compared with each other at the same level. The small mollusk Heleobia sp. was excluded in this last analysis because the abundance masks the rest of the species. ...
Chapter
Archaeological faunal remains from the humid tropics have long been known to suffer from poor preservation which hinders biomolecular approaches to objective species identification and phylogenetic analysis using DNA. However, a new technique of collagen analysis by soft-ionization mass spectrometry offers a means to access such molecular information from the tropics that are typically regions of greatest worldwide biodiversity. This work explores the application of collagen analyses to remains of a dwarf deer of uncertain ancestry discovered in a ~6000 year old shell-bearing midden on Pedro González Island (Panama). The sub-fossil deer’s tiny size, the extreme cultural modification of >2400 specimens, and the rarity of complete bones and antlers prevented objective identification below Family level. Collagen fingerprinting analyses reveal that both the Pedro González island archaeological deer and an extant small deer on San José Island 8 km away, are closely related but do not have a close affinity with the Central American red brocket deer (Mazama temama Kerr 1792). Using these methods, their closest affinity appears to be with a group of cervids that comprises the North and Central American white-tailed deer (Odocoileus virginianus Zimmerman 1780) and populations of the Amazonian brown brocket deer (M. nemorivaga Cuvier 1817).
... The RSL highstands of the Holocene along southeast Australia are +1-2 m at ca. 2000-8000 yr B.P. (Lee et al., 2016), along the Great Barrier Reef they are > −0.30 m at 5500 and 4600 yr B.P. (Leonard et al., 2016), in the southwest Pacific Ocean +1.1 m at 4500 cal yr B.P. (Yamano et al., 2014), but in the Central Pacific Ocean +2.5-3.0 m at 4800-4000 yr B.P. (Kench et al., 2014) and in Japan +1.9 m at 6400-6500 yr B.P. (Chiba et al., 2016). Along the Persian Gulf, they are > +1 m at 5290-4570 cal yr B.P. (Lokier et al., 2015, their Table 5), in the Atlantic region, in Uruguay, 0 m at 4700-4300 yr B.P. (Bracco et al., 2014), and in Brazil +2-4 m at 3900-3200 yr B.P. and + 2 m at 2700-2100 cal yr B.P. (Spotorno-Oliveira et al., 2016, their Table 1). This lack of uniformity has been explained by GIA effects (Mitrovica and Peltier, 1991;Mitrovica and Milne, 2002;Milne and Mitrovica, 2008). ...
Article
The eastern coast of Fuerteventura (Canary Islands, Spain) hosts the most complete and representative emergent Holocene marine deposits in the middle latitudes (27ºN to 30ºN) of the eastern Atlantic Ocean. The deposits consist of berms of gravel and foreshore sands which form beach rocks comprising more than 62 bed sets, with each bed set containing dozens of individual laminations suggesting a cyclical cause as, for example, the orbital movement of the Earth. Calibrated radiocarbon ages place a group of older Holocene highstands of Fuerteventura at around the Mid-Late Holocene boundary (around 4.2 kyr B.P.), and another group of more recent highstands in the Dark Age Period (around 1.4 kyr B.P.) of the Northern Hemisphere. They have been recorded at 4 m and 3.5 m apmsl respectively. The present-day tidal amplitude is around 3 m. Assuming a similar value for the Holocene, the corresponding relative sea level rises were around 2.5 m and 2 m apmsl respectively. Moreover, terrestrial deposits intercalated between the marine deposits indicate a lowering of the sea level at ca. 3 kyr B.P. When the sea levels reached their highstands during these two periods, the sea surface temperatures (SST) at the southern tip of the cold Canary Current were, respectively, 0.5 and 1.5ºC colder than the present-day SST (21.23ºC). The fossil fauna content confirms that these highstands occurred in cold conditions. In contrast, the present SST reaches the range of temperatures of the Holocene Optimum in the area. Fuerteventura has been vertically stable since the last interglacial period, and the sedimentology of the deposits precludes an origin from tsunamis or storms. This island is in a far-field region in terms of glacial isostatic adjustment (GIA) processes. Here, we suggest that the deposits may be related to GIA and ice mass losses effects in the Southern Hemisphere.
... Almost all scientific references regarding RSL developed on the east coast of South America reveal a sea-level higher than MSL at around 5000 yrs BP (Martin and Suguio, 1975;Suguio et al., 1976Suguio et al., , 1985Martin et al., 1979Martin et al., , 1998Angulo and Lessa, 1997;Isla, 1998;Bezerra et al., 2003;Cavallotto et al., 2004;Angulo et al., 2006;Martínez and Rojas, 2013;Bracco et al., 2014;Cunha et al., 2017;Prieto et al., 2017;Castro et al., 2018;Tâmega et al., 2019). According to , between 5500 and 4500 cal yrs BP, RSL has reached the first Holocene peak with a maximum height of 2.5 m above MSL, the last maximum peak of the Holocene transgression in southeastern Brazil, which the authors named as "the Cabo Frio Transgression". ...
Article
A review of relative sea-level (RSL) oscillations during the Holocene in Rio de Janeiro, southeastern Brazil, is presented based on new data. This new data encompasses analytical techniques, altimetric corrections and age recalibrations, using the marine local radiocarbon reservoir correction of 96 ± 48 yrs. The effectiveness of geological and biological RSL indicators was tested, aiming to provide consistent information for future researches on the east coast of South America. Results confirm that RSL during Late Pleistocene - Holocene transition (11,970–11,122 cal yrs BP) was 4.5 m below Mean Sea-level (MSL). After that transition, a relatively rapid rise began. At approximately 7948–7598 cal yrs BP, the MSL was 0.5 m below the current marine level. Present-day, “zero”, was reached for the first time in the Holocene, at approximately 7686–7269 cal yrs BP. The maximum level of the Holocene marine transgression occurred around 4787 - 4104 cal yrs BP with a height of 3.0 m above MSL. At the point of maximum transgression, the sea-level began a general behavior of lowering. However, between 3981 and 3345 to 1852 - 1413 cal yrs BP, evidence from vermetids suggests several alternating periods of slow and rapid sea-level, identified by four oscillations. New records, between 1220 - 780 and 1055 - 665 cal yrs BP, have indicated a continue lowering trend of RSL.
... Bracco-Boksar et al. (2011), combining evidence with varying reliability, and not adjusting for the height of the deposition, constructed by hand a curve based on the deposits around the current Rocha Lagoon, and concluded that the maximum Holocene sea level was reached approximately 6,000 years ago, and that since then there has been a fluctuating declining trend. According to Martínez and Rojas (2013), who statistically used data from old berm deposits corrected for the height of the deposition, the maximum sea level (around 3 m above the present sea level) was reached also around 6,000 years ago, but that after that there was a smooth lowering of the sea level ( Fig. 2.14) (see also Bracco et al. 2014;Martínez and Rojas 2014;Mourelle et al. 2015). According to numerical ages, arranged in updated tables, correlation with the Marine Isotope Stage 3 (MIS-3) and MIS-2 is discussed for southern and northern Late Pleistocene beds. ...
Chapter
Marine and transitional Quaternary deposits in Uruguay provide useful information about past sea levels and climatic and environmental changes over the last thousands of years. They yield abundant molluskan faunas that are crucial for these interpretations, and other invertebrates, vertebrates, ichnofaunas, microfaunas and microfloras. These deposits have been classified in a disorderly way over the years with a large number of stratigraphical units, but they can be reduced to two: the Pleistocene Chuy Formation, and the Holocene Villa Soriano Formation. They represent two main invasions of the sea, which displaced the Rio de la Plata estuary westward and northwestward. This phenomenon, and, logically, the rising sea level, was more intense in the Pleistocene. The fossil content not only gives proof of the relative temperature and salinity changes, but also of the level of the sea, and the age (since shells are very good material for radiocarbon dating). In the Late Pleistocene (MIS 5e) the sea level was about 6–8 m above the present level, and in the Holocene reached a maximum of 3 m above the present level, smoothly declining later. During both transgressions, the temperature was higher than at present, and faunal displacements have been verified; once again, these phenomena were clearly more intense in the Late Pleistocene. A considerable number of radiocarbon ages have been recorded, as well as some optically stimulated luminscence (OSL) ones.
... Bracco-Boksar et al. (2011), combining evidence with varying reliability, and not adjusting for the height of the deposition, constructed by hand a curve based on the deposits around the current Rocha Lagoon, and concluded that the maximum Holocene sea level was reached approximately 6,000 years ago, and that since then there has been a fluctuating declining trend. According to Martínez and Rojas (2013), who statistically used data from old berm deposits corrected for the height of the deposition, the maximum sea level (around 3 m above the present sea level) was reached also around 6,000 years ago, but that after that there was a smooth lowering of the sea level ( Fig. 2.14) (see also Bracco et al. 2014;Martínez and Rojas 2014;Mourelle et al. 2015). According to numerical ages, arranged in updated tables, correlation with the Marine Isotope Stage 3 (MIS-3) and MIS-2 is discussed for southern and northern Late Pleistocene beds. ...
Chapter
The marine and estuarine beds of Uruguay may be roughly ascribed to two groups, one belonging to the Late Pleistocene and other to the Holocene. In the past, many names and units were introduced in the literature, mainly designating facies, but currently, and thanks to a good data base of numerical ages, we can simplify this former, almost anarchic situation, with the correlation by numerical ages made much easier. In Uruguay, the Pleistocene deposits correspond to MIS 5e, and the Holocene ones to its middle and late part, with equivalent deposits in southern Brazil and northern Argentina. The identification of units in these areas suffered the same vices; consequently, it is wise to correlate the quaternary deposits on an age-only based framework. The continental beds correlate with the Pampean and Mesopotamian areas of Argentina and southern Brazil. The fluvial Salto Formation of western Uruguay has been chronologically/lithologically correlated with beds of the Argentinian Mesopotamia (El Palmar Formation, Salto Chico Formation and Ituzaingó Formation). The sedimentary beds of northern Uruguay (Sopas Formation) are lithologically and chronologically correlated with the Touro Passo Formation of southern Brazil, reflecting fluvial and aeolian depositional processes, mostly related to the MIS-3. The sedimentary beds of southern Uruguay, the Dolores Formation, correlates in age with Late Pleistocene beds of the Pampean region of Argentina (the Guerrero Member of the Luján Formation), mostly related to the influence of the MIS-2.
... This hybrid zone movement could be associated with major basin transformation. In this sense, some authors have reported the capture of alluvial fans located in the South as part of the Cebollatí river in the DMS drainage, during the Holocene, as a clear demonstration of its recent activity and the extensive reorganization of this basin [19,64]. ...
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The genus Austrolebias (Cyprinodontiformes: Rivulidae) represents a specious group of taxa following annual life cycles in the neotropical ichthyofauna. They live in temporary ponds and each generation must be completed in a few months, depending on environmental stochasticity. Annual fish survive the dry season through diapausing eggs buried in the substrate of these ponds. A hypothesized bimodal hybrid zone between two taxa of the genus, A. charrua and A. reicherti from Dos Patos Merin lagoon system, was recently proposed based on genetics and morphological analyses. However, hundreds of additional nuclear molecular markers should be used to strongly support this hypothesized bimodal pattern. In the present paper, we conducted RNA-seq-based sequencing of the transcriptomes from pools of individuals of A. charrua, A. reicherti and their putative natural hybrids from the previously characterized hybrid zone. As a result, we identified a set of 111,725 SNP (single nucleotide polymorphism) markers, representing presumably fixed allelic differences among the two species. The present study provided the first panel of 106 SNP markers as a single diagnostic multiplex assay and validated their capacity to reconstruct the patterns of the hybrid zone between both taxa. These nuclear markers combined with Cytb gene and morphological analyses detected a population structure in which some groups among the hybrid swarms showed different level of introgression towards one or the other parental species according to their geographic distribution. High-quality transcriptomes and a large set of gene-linked SNPs should greatly facilitate functional and population genomics studies in the hybrid zone of these endangered species.
Article
Dispersal ability can enhance the probability of an organism surviving and reproducing, and affects the geographic structure of its genetic variability. Allocosa senex is a nocturnal sand-dwelling wolf spider strictly associated with oceanic, estuarine and freshwater sandy coast habitats of southern South America, including Uruguay, Brazil, and Argentina. Recent research has revealed the presence of diverse dispersal strategies, both aerial and aquatic. Here we investigated the genetic structure and demographic history of A. senex using sequences of the mitochondrial genome and genomic scanning using amplified fragment length polymorphisms (AFLPs). We hypothesized the presence of a weak population genetic structure in space because of high levels of gene flow. We analysed individuals from 21 localities from Uruguay, Argentina, and Brazil. We obtained 60 sequences for the cox1 (17 haplotypes) and 445 AFLP polymorphic loci of 90 individuals. The results were in agreement with our hypothesis. They revealed an absence of spatially structured genetic diversity, neither among localities nor among basins, suggesting little isolation by distance in the group. The mitochondrial gene tree was dated and age estimates revealed a recent origin of A. senex, which was traced back to the Middle Pleistocene. Both the mitochondrial star-like topology and the departures from neutrality, further supported by the lack of AFLP population structure and isolation by distance, are in agreement with a recent population expansion. Demographic changes could be related to climatic oscillations and geological changes undergone by the study area during the Pleistocene.
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This article aims to advance in the knowledge of the relationships between the sand cycle and the behaviour of small river mouths (outlets) flowing into sandy beaches in the Río de la Plata estuary, Uruguay. The bars of these watercourses respond quickly with processes of erosion and/or migration of the channel when the “sand cycle” (coastal sedimentary balance) undergoes modifications, due to i) the effect of the fixation of dunes (sediments) by afforestation with exotic species and ii) the construction of infrastructure. Two watercourses were analysed: the Pando River and the Carrasco Creek that both have received different impacts and suffered modifications, not only in the sediment flow but also in their hydrological regime. A multitemporal analysis was based on a series of aerial photos and cartography since 1928, a background review, and the support of documents and chronicles. The data obtained were analysed statistically. Results evidence a significant loss of beach surface at the Pando River mouth, and an increase at the Carrasco Creek mouth, since the channelling of a wetland located upstream, allowing the entrance of sediments from the basin upstream of the wetland. Relevant outcomes are: i) the description and analysis of the relationships established between dune systems and the outlets of the watercourses, an aspect that has not received due attention in the scientific literature, in which the dissociation between the analysis of wind and fluvial dynamics is usual, and ii) the sedimentary balance was of both systems: erosion and accretion at the Pando and the Carrasco outlets respectively. The reconstruction of the dunes could likely prevent the escape of sand and reduce the erosion. The knowledge about human intervention and natural processes governing the interactions between sandy beaches, dunes and outlets is a crucial input to coastal management and adaptation to sea-level rise and storm surges.
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Paleolimnología de cuerpos de agua someros del sudeste del Uruguay: evolución holocena e impacto humano – Hugo Inda 2
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The coastal zone of Uruguay experienced considerable paleoenvironmental changes during the last 30,000 year BP. In the Pleistocene, most of the coast exhibited terrestrial arid/semiarid and cool conditions. The Pleistocene–Holocene transition was characterized by a climatic amelioration toward warmer or more humid conditions. After the first Holocene transgression, marine/brackish aquatic systems were established. Dominance of marine/brackish diatoms together with relatively low trophic state conditions and sandy sediments were recorded. Such conditions prevailed until the Holocene sea-level maximum (i.e., ~5,000 year BP). Once the Holocene regressive phase started during mid-Holocene, the onset of brackish/freshwater conditions was observed. Concomitant increases in freshwater/brackish diatoms, trophic state, and silt sediments were observed in the sedimentary profiles. High variability in climatic conditions during mid-Holocene was recorded, as different authors have proposed different paleoclimates in terms of humidity and temperature. However, most of them observed dry conditions during mid-Holocene, with an increase in both temperature and humidity toward late Holocene. After ~1,000 year BP, some of the coastal water bodies became separate from the ocean. Dominance of freshwater diatoms and changes in trophic state were observed. In the case of Lake Blanca, the separation from the ocean took place during a climatic deterioration, and both nutrient depletion and a decrease in trophic state were observed. In the case of Negra Lagoon, the separation process took place during a climatic amelioration and increases in trophic state were observed. This suggests that long-term trophic state of coastal systems might be controlled by both sea-level changes and climatic conditions. During the Anthropocene, after human intervention, several eutrophication episodes were tracked by means of paleolimnological techniques, thus suggesting the need for paleolimnological studies in developing countries where long-term limnological data are unavailable.
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Paleolimnological methods were used to track the Late Pleistocene and Holocene development of Castillos Lagoon, SE Uruguay. During the Late Pleistocene, the system showed terrestrial characteristics as the sediment core contained neither diatoms nor chrysophyte cysts. After an aquatic system established, dominance of marine/brackish diatoms was observed, which indicates the occurrence of a marine/brackish coastal system. Increases in relative abundance of freshwater diatoms were observed during regressive events, thus suggesting a decrease in salinity levels. Higher trophic states were observed during regression than transgression events, probably because of increased runoff and erosion as regressions took place. The same relationship between trophic state, diatom species composition and sea level variation, had been observed in other coastal systems of SE Uruguay.
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Use of the term 'beach ridge' is confusing in the literature because definitions of beach ridges are highly variable and are commonly used interchangeably with 'berm' and sometimes 'foredune'. Thus, the definitions of sand beach ridges are briefly reviewed, and beach ridges are re-defined as entirely wave formed deposits. Berms and foredunes are also defined. Modes of sand beach ridge formation are also reviewed, with four primary modes identified.
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La preocupación creciente por los perjuicios que el calentamiento global pueda producir ha motivado que el ascenso del nivel del mar pasara a estar dentro de nuestras preocupaciones cotidianas, tomándose conciencia que el nivel del mar puede variar y ha variado a lo largo de los tiempos geológicos. En el campo de las ciencias, clima y nivel marino se habían vinculado a partir del reconocimiento, a principios del siglo XX, de los períodos glaciales que caracterizan el Pleistoceno. Estas líneas de investigación demostraron que en los últimos 2.5 Ma, los océanos han ascendido y descendido en el orden de decenas de metros -no de centímetros- durante los períodos interglaciales y glaciales, respectivamente. Pero también en muchas zonas litorales ascensos o descensos locales o regionales del continente, principalmente por tectónica o isostasia, acompañaron las variaciones glacioeustáticas, lo que ha llevado a que se acuñara el concepto de «niveles relativos del mar». El mayor descenso glacioeustático para el Pleistoceno se observa durante el Máximo de la Última Glaciación, hace ~26 ka, cuando se produce la mayor retención de agua en los mantos de hielo continental. El nivel de los océanos se ubicó ~ -120 m. A partir de este momento, acompañando el mejoramiento climático que llevará al Holoceno, el océano ascendió rápidamente para situarse en el nivel actual, en el ~8 ka. Regionalmente este ascenso significó que nuestra plataforma continental quedara bajo agua, se formara el estuario Río de la Plata y se ubicara la línea de costa en una posición muy cercana a la que hoy conocemos. Hacia el 6 ka AP el ascenso glacioeustático cesa, al alcanzarse el «Máximo del Transgresivo del Holoceno». Las posteriores variaciones del nivel del mar que se observan mundialmente son atribuidas a procesos de redistribución de las masas de agua. Es a partir de ese momento que en nuestras latitudes se forman las evidencias más visibles en nuestros registros de las variaciones en la línea de costas ocurridas durante el Pleistoceno final-Holoceno. Son depósitos y sus geoformas que no han quedado sumergidos y que testifican un progresivo descenso desde el nivel más alto alcanzo durante el Holoceno Medio, a ~+ 4 m, hasta el nivel actual. Estas evidencias tienen su mayor expresión en las lagunas costeras cuyo origen se encuentra en el Máximo del Transgresivo del Holoceno. Presentamos los datos de las variaciones relativas del nivel del mar obtenidos en la laguna de Castillos y el comportamiento de los niveles del mar inferidos a partir de ellos. Por último, se compara este comportamiento con los propuestos para las costas próximas de Brasil y Argentina. Cierra una reflexión sobre evolución humana y cambios del nivel del mar.
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Las lagunas costeras uruguayas representan el límite austral de un sistema que abarca una extensa zona que se extiende desde Santa Catarina (Brasil) hasta el departamento de Canelones (Uruguay). La geomorfología como disciplina que ayude a la interpretación del origen y evolución de estos sistemas, solo ha sido reconocida recientemente, existiendo aun pocas aproximaciones al tema en la literatura científica. Las lagunas costeras desde un punto de vista físico pueden caracterizarse como depresiones que responden a diferentes situaciones y condiciones; algunas han sido formadas en las ensenadas o en las partes terminales de las planicies de inundación de los ríos, otras son de origen tectónico y otras se forman por la acumulación de sedimentos arrastrados por las corrientes marinas en planicies de abrasión generadas durante las ingresiones pleistocénicas y holocénicas. Todas estas unidades ecológicas se diferencian de los estuarios por sus rasgos geomorfológicos, sin embargo sus características biológicas, físicas y químicas son similares. Los procesos que dieron origen a la formación de nuestras lagunas costeras se remontan en algunos casos al Pleistoceno superior. Por su importancia pueden destacarse aquellas lagunas y lagos costeros o lagunas cerradas, lagunas de origen fluvial (oxbow), restos de antiguas lagunas pleistocénicas, paleocanales de mareas, charcas interdunares de deflación eólica, de claudicación de sedimentos modernos, de disolución de carbonatos, y pequeñas charcas de origen biológico. Una de las características geomorfológicas analizadas y que permiten comprender procesos biológicos, es la apertura de las lagunas semicerradas, que permite el intercambio de agua con el Atlántico y el Río de la Plata. Otra característica geomorfológica importante es el grado de evolución de los cuerpos de agua relativo a la circulación interna de la laguna, generada por su índice de circularidad, la circulación interna y la cantidad de cuerpos aislados o semiaislados escondidos de la misma. Las principales lagunas son analizadas individualmente en la medida en que su evolución posterior ha generado particularidades en su estructura geomorfológica, importantes en relación a los ecosistemas que las mismas poseen, haciendo énfasis en particular en la Laguna de Castillos por su particular interés geomorfológico, biológico y cultural.
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Many prograded barriers and some dunefields in theworld have been termed ‘beach ridge’ plains, but the actual genesis of the ‘ridges’ is often unknown. Use of the terms, berms, beach ridges and foredunes is also confusing in the literature because their definitions are highly variable and are commonly used interchangeably. Thus, the formation and definition of sand berms, beach ridges and foredunes is briefly reviewed. Beach ridges are re-defined as entirely wave formed deposits which are most commonly formed during high wave conditions and/or elevated water levels (e.g. storm surges). Foredunes are formed by aeolian sand deposition in vegetation on the backshore. Some dunefields in Brazil have been called beach ridge plains when they are, in fact, foredune plains, transgressive dunefields, or complex barriers (i.e. barriers comprising two types of dunes). The Holocene barrier extending from Torres to Tramandaí in southern Brazil has been regarded as a beach ridge plain. The landforms of this Holocene barrier comprise wide, relatively linear, widely spaced (400–600m), shore parallel ridges on the landward half, and more closely spaced (80–400m), lobate and crescentic, discrete ridges on the seaward half. Low, rolling dunefields, sand sheets, nebkha fields and deflation plains occur between the ridges. The barrier is re-interpreted as a prograded, transgressive dunefield barrier.
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Opal phytolith, geochemical and sedimentological data from two cores taken in Peña Lagoon, a small water body on the Atlantic shore of Uruguay, are presented in this paper. The choice of this specific sampling location aimed to obtain high resolution records to infer late Holocene environmental and climatic changes in southeastern Uruguay, in order to improve previous models for early and middle Holocene. The combined record of two cores extends to 2500 14C BP, with a sedimentation rate ranging between 0.6 and 2 mm y−1. A multiproxy approach allowed the identification of changes in dynamics, particularly organic matter and sediment input variability from the watershed. With this information, differences in the amount and extent of environmental signals were evaluated and a comprehensive climate change model was generated, especially for the last 1500 years. Three main climatic events were distinguished. The oldest, which lasted until 700 AD, was characterized by temperate and humid conditions. The second extended until 1200 AD and warmer and wetter conditions were inferred, but also a colder and drier pulse was observed in between. This second event was assigned to the Warm Medieval Period (WMP). During the third event, assigned to the Little Ice Age (LIA), which extended until the present, a high variability in climate was observed, but also three dry/cold phases reaching their maxima by 1300, 1600 and 1900 AD were inferred.
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Several hypotheses have been proposed to explain the origin of death assemblages of stout razor clams Tagelus plebeius buried in Life position found in Holocene sediments in coastal Argentina and Uruguay: (1) a rapid decrease of sea level, (2) obstruction of the mouth of a coastal lagoon and episodic deposition of fluvial sediments in the mouth of a creek, and (3) a 'taphonomic feedback' process. Hypothesis 1 has been discarded, Hypothesis 2 only has a local explanation, while based on current information Hypothesis 3 is unlikely. A bird predation hypothesis is proposed here on the basis of a study of an extant population. The density of an extant population at the Mar Chiquita coastal lagoon, Argentina (37 degrees 46'S, 57 degrees 27'W), is higher in the lower intertidal (up to 200 clams m(-2)) and decreases towards the upper intertidal, and clam size is correlated with burial depth. However, Live individuals there coexist with large densities (up to 1500 clams m(-2)) of dead clams in life position, with densities peaking at the middle-upper intertidal. These shells showed no size-depth of burial correlation. Stout razor clams in fossil deposits (1500 yr BP) also showed large densities of shells in Life position (528 clams m(-2), SD = 16, n = 20) with no clam size-burial depth relationship. Predation by the American oystercatcher Haematopus palliatus is an important cause of mortality year-round, taking 28 clam h(-1) during 3:43 h d(-1). Half of the successful attacks left shells in Life position buried in the sediment. A computer simulation based on this information showed that predation by 1 oystercatcher produces 9.2 life-position shells m(-2) yr(-1) (SD = 3.7 life-position shells m(-2) yr(-1), n = 10 000). Thus, 89.5 yr (95% CL = 50-422 yr) are required to generate a mean shell density similar to the one found on our study site (824 clams m(-2)). Thus, predation by oystercatchers generates a pattern similar to fossil assemblages and is the most likely explanation for the Holocene shell assemblages of the stout razor clams.
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The strong correspondence between the spatial arrangement of archaeological sites and wetland environments is one of the main axes of the Merín Lagoon basin archaeology. Without implying a deterministic simplification from the epistemological point of view, the cultural and environmental history of the region hold evidence suggesting a more complex scenario, where cultural responses to climate change were not so mechanical or direct as previously argued. The relationship between paleoclimate and prehistoric mound builders development between 7.0 and 0.6 ka 14C BP was studied in SE Uruguay. Paleoclimatic data were inferred from the phytolith record of three lagoon sediment cores. Four paleoclimatic periods were identified according to temperature/humidity changes. The first period, dated at 7.0–4.5 ka 14C BP, was characterized by a warm/humid climate. Between 4.5 and 3.5 ka 14C BP, the onset of a cool/dry climate was inferred. A hiatus between 3.5 and 2.6 ka 14C BP was identified. In the third period, 2.5–1.2 ka 14C BP, similar climate conditions to those of the present were inferred. Finally, the period 1.2 and 0.6 ka 14C BP, was characterized by warmer and wetter conditions than those of the present. According to these data, it was determined that mounds were first observed during the transition from warm/humid to cool/dry conditions, but the complexity of the mounds increased after the full establishment of cool/dry conditions. With the inception of warm/humid conditions, an increased number of mounds was observed in the plains located close to the Merín Lagoon littoral. The mounds showed lower density and height than those recorded for the cool/dry period. This behavioral modification in mound construction was explained because of the paleoenvironmental change.
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Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142km2 coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000yr BP), cool–dry climatic conditions were established. After ~4000yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700yr BP. Such climatic amelioration led to increases in trophic state.
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Paleolimnological data are presented on trophic development, climatic change and sea level variations in Rocha Lagoon, a 72km2 coastal lagoon in southern Uruguay. Using a sediment core that extended from 7000 to about 3700yr BP, analyses of organic matter, carbonate, diatoms and chrysophyte cysts were used to track the early Holocene paleolimnological conditions of Rocha Lagoon. Opal phytoliths were also counted and identified, both temperature and humidity indices were calculated, and Opal Phytolith Association Zones (OPAZ) were identified by performing Principal Coordinates Analysis (PCO). Diatom Association Zones (DAZ) corresponding to marine/brackish and brackish/freshwater episodes were closely related to changes in trophic state. Those DAZ representing marine/brackish stages exhibited a lower trophic state than those DAZ dominated by brackish and freshwater diatoms. This highlights that during the first Holocene marine transgression, Rocha Lagoon did not continuously exhibit marine/brackish conditions as reported in previous papers. Instead, three brackish/freshwater episodes related to sea level variation and changes in humidity were identified. The first episode, by ~6000yr BP, was related to sea level change as no significant changes in either temperature or humidity indices were observed. The second episode, between 5000 and 4400yr BP, was related to both a sea level decrease and an increase in humidity, as a transition from humid to very humid climate was inferred. Concomitant decreases in salinity and increases in trophic state were also observed. The third episode, after ~4000yr BP, was related to the end of the first Holocene regressive phase when sea level was slightly below present levels. Further decreases in salinity and increases in trophic state were detected. The paleoclimatic trends inferred in this study were in close agreement with other regional studies on climatic change, as cool temperatures were inferred. However, major changes in humidity were also detected. A humid to very humid climate was inferred for ~7000–4500yr BP, but the occurrence of a semiarid/arid climate was inferred for ~4500–3700yr BP. Our data suggest that during transgressive and regressive events there might be higher frequency and lower amplitude sea level oscillations that might lead to changes in salinity and trophic state of coastal aquatic systems. Such oscillations could only be tracked by high resolution analyses of sedimentary records and could be best interpreted with complementary data on paleoclimate. In addition, microfossils such as diatoms and opal phytoliths were shown to be very sensitive to such paleoenvironmental changes.
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Paleolimnological data are presented relating trophic development to sea level variation in Lake Blanca, a small (0.6 km2), coastal fresh waterbody in southern Uruguay. Using a sediment core that extended to 7300 years BP, analyses of grain size, thin sections, organic matter, carbonate, total carbon, nutrients, diatoms and palynomorphs, allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regression progressed. Four diatom association zones (DAZ) were identified in the sediment core. The basal core section pre-dated the first Holocene marine transgression, contained no diatoms, chrysophyte cysts or non-siliceous microalgae, and showed C/N ratios values higher than 20. Thus, it is likely that the system exhibited terrestrial characteristics. In the second section (6500–2200 years BP, following the first Holocene transgression), there was dominance of marine/brackish diatom species. The lowest trophic states of the core were observed in this section. The third section (2200–1100 years BP), represented the system as it became separate from the Atlantic Ocean, and showed a dominance of brackish/freshwater species and increases in trophic state were observed. In the last section (after 1100 years BP), the system became fully freshwater as no marine or brackish diatom species were found, but a trend to oligotrophication was observed, probably due to nutrient depletion. However, after 1967 AD, eutrophication intensified because of forestry and soil fertilization in the catchment. Pollen association zones (PAZ) allowed us to identify four sections. Below 250 cm (2200 years BP), the core contained no pollen grains as redox potential and pH values were not conducive for pollen preservation. After 2200 years BP (when the system started to separate from the ocean), xerophilic taxa typical of coastal dunes colonized the catchment. Only after 1100 years BP (after fully freshwater conditions established) pollen grains of trees were observed.
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Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system.
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New limnogeological results (Laguna Mar Chiquita, 30°S) at the middle latitudes in the subtropical Pampean plains of Southern South America are used to establish comparisons with records spanning Late Glacial times and the Holocene covering the Northern Andean Patagonia and the Extra Andean Southern Patagonia. Historical and archaeological data were also used to enlarge existing environmental reconstructions in the central plains of Southern South America. Two groups of climate records – at both sides of the Arid Diagonal- can be distinguished according to their hydrological response during dominant warm or cold climatic phases. The first group includes records from the Pampean region and allows to reconstruct the past activity of the South America Monsoonal System. The second group includes archives of the Patagonian climate, as well as the Salinas del Bebedero, and provides a record of past changes in the strength and latitudinal position of the Southern Westerlies. KeywordsPampean lakes–Late-Pleistocene/Holocene hydrological reconstruction–Arid Diagonal–South American Monsoon System vs. Westerlies
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Data on chrysophyte cyst to diatom ratios as an index to track Holocene paleosalinity changes are presented. Six sediment cores taken in four coastal systems influenced by Holocene sea level changes indicate that during the transition from marine/brackish to brackish/freshwater and freshwater conditions, increases in the cyst to diatom ratio were recorded. These data suggest that Holocene changes in paleosalinities in coastal aquatic systems may be tracked by using this simple index, however other factors (such as changes in nutrient levels) may complicate some interpretations. Nevertheless, data required to calculate this simple index are easy to obtain, and so relatively little effort is required to obtain some paleolimnological information on these two important algal groups.
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Paleolimnological data are presented on Holocene climatic changes in Lake Blanca, a small (0.6km2), coastal fresh waterbody in southern Uruguay. Using a sediment core that extended to 7,300year BP, analyses of pooid, panicoid and chloridoid phytoliths (Poaceae) allowed us to identify 16 Opal Phytoliths Association Zones (OPAZ). Both temperature and humidity indices were calculated from relative percentages of opal phytoliths and the climatic trends were inferred. During the early Holocene, prior to the first Holocene marine transgression (∼ ∼8,000–7,000yr BP), cool-arid climatic conditions were inferred. After the first Holocene transgression, predominance of cool-humid conditions was registered until about 4,000yr BP. A transition from cool-semiarid/arid to alternate warm-temperate and humid-very-humid conditions was detected for ∼∼4,000–1,000yr BP. Increases in trophic state were observed because of such a climatic amelioration. After ∼ ∼1,000yr BP, a shift from warm to temperate and cool temperatures was inferred. Such a cooling episode was assigned to a “LIA” which took place by the end of the 18th century and the beginning of the 19th century. A decrease in trophic state was observed during this climatic deterioration. After such a little ice age, present temperate humid conditions were established. The humidity indices calculated from relative percentages of opal phytoliths for the last ∼ ∼70years were compared to annual rainfall data. Such a comparison showed that opal phytoliths are reliable indicators of humidity.
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The de la Plata river, considered from the geomorphologic point of view, can be defined as a unit composed of a set of features genetically linked together which were formed as a result of the post-Last Glacial Maximum transgression. Regional stratigraphical, morphological and topographical studies carried out in the de la Plata river and surrounding areas of eastern Argentina determined that the Holocene evolution of the area was the result of processes resulting from relative sea-level fluctuations. In order to date the different stages of evolution, a curve of sea-level fluctuations was constructed after a selective choosing of samples with reliable ages supported by field geological evidence.The curve shows a rapid initial transgressive event and the maximum highstand of mean sea level at 6000 yr BP at a relative elevation of +6.5 m above present. The following regressive event was characterized by a discontinuous fall in sea level.Geomorphological evidence suggests that sea-level fall could have experienced minor changes in rate as well as moments of stability that are not shown by the curve. Short interruptions in the geological record can be explained either by the same minor changes in sea level or by a change in wave regime. Correlation of transgressive–regressive events with paleoclimatic and biogeographic information proposed that Holocene sea-level fluctuations in the de la Plata river were mainly controlled by climatic changes.
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This paper reviews the relationship between prehistoric mounds (5000 years BP to 17th century) with main landscape features, particularly wetlands, in the east of Uruguay. Former archeological researchers did recognize this relationship, but it was interpreted by extrapolating current environments to 5000 years of cultural behavior. In an effort to better understand how environmental dynamics were linked to the cultural record, a set of proxy records (diatoms, opal phytoliths, gastropods, shells) were introduced to take into account local environmental evolution data according to global and regional environmental evolution models. The main environmental events during the mid and late Holocene show a high correspondence with mound builders’ spatial arrangements.
Article
Relative sea-level curves have been delineated for several sectors of the Brazilian coast. In order to have homogeneous and consistent curves, very short segments of the coastline with the same framework are considered. To minimize systematic errors tied to the particular nature of an indicator, we use the maximum number of different indicators available from former positions of relative sea level. These sea-level curves show that, during the last 7000 years, the central Brazilian coast has been subjected to a submergence phase which lasted until 5100 14C yr BP (5600 cal yr BP), followed by a drop in sea level. This drop in sea level was not continuous but was interrupted by two high-frequency oscillations. The Salvador curve, the most detailed, can be used as a reference for the central portion of the Brazilian coastline. It is now presented with corrections for isotopic fractionation and reservoir effects as well as calibrations for astronomical ages. Additional supporting evidence for the existence of these high-frequency oscillations is provided.
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This chapter deals with Eolian deposits, consisting of both dune and sheet sand in South and North America. Much of the loess present on both continents, which are derived from glacial outwash sources and deposited during the last glacial maximum. Cold, dry, windy conditions during the last glacial period have favored loess deposition from a variety of sources. Eolian sand is extensive on both the continents. Holocene eolian sand is abundant in the Pampas region of South America. Deep-sea sediment cores, ice cores, and soils contain long-term records of the dust flux. Deposition of loess and eolian sand, from multiple sources during the last glacial period, agrees with pollen records, lake records, and COHMAP (Cooperative Holocene Climate Mapping) climate simulations. In the Pampas region of South America, there is at least fair agreement between summer surface winds simulated by COHMAP and paleowinds as recorded by eolian sand and loess. In mid-continental North America, however, the presence of a strong glacial anticyclone centered over the Laurentide ice sheet generates northeasterly winds in the region immediately to the south of the ice sheet. Both eolian records and lacustrine records indicate that there are multiple periods of relatively dry climate during the late Holocene.
Article
The reconstruction of relative sea-level changes, during the last 7000 years, has shown that the central Brazilian coast was been subjected to submergence until approximately 5100 yr. B.P. However, the emergence after 5100 yr. B.P. was interrupted by two important fluctuations with an amplitude of approximately 2–3 m and a duration of 200–300 yr. This evolutionary history, which is quite different from that of several other regions in the world, played an essential role in the development of the central Brazilian coastal plains, whether or not they are associated with important river mouths. The periods of submergence, characterized by erosional phases, introduced noticeable changes in the geometry of the coastal deposits. The periods of emergence gave rise to sandy terraces covered by beach-ridges whose orientation is determined by the longshore drift. Elsewhere on a low sandy coast, the direction of longshore sand transport depends on the orientation of the swell. In a coast subjected to various swell patterns the efficient swells are defined as those which determine the resulting longshore transport direction. Such swells are not necessarily the most prevalent. For instance, along the central Brazilian coast the southern sector waves, in spite of their infrequent occurrences, are much more powerful than the northern sector waves and therefore generate a longshore sand transport from south to north.
Article
Loess and loessoid (loess-like, reworked loess) sediments extend across the Chaco–Pampean plains and the NW mountain environments of Argentina, and in neighbouring countries (Paraguay, Brazil, Uruguay, Bolivia). Loessoid sediments are much more abundant than primary loess. The beginning of the loessoid sedimentation cycle was related to a phase of Late Miocene orogeny in the Andes. The Plio-Pleistocene record is mostly composed of loessoid sediments modified by pedogenesis, which produced welded palaeosols. The Late Pleistocene/Holocene loess record reveals a heterogeneous composition across the region. Coarse textures and an Andean-derived volcanic composition prevail in the southern Pampas. Finer textures and material coming from the Andes and the other two sources (Sierras Pampeanas and the Paraná basin) characterize the loess deposits of the northern Pampas and the eastern Chaco. A southern Patagonian source is also suggested for the mountain valley loess of Tucumán, although a western Andean provenance has been proposed. It is believed that the material in the western Chaco was derived from the Bolivian Andes. Loess deposition was related to a multistage transport mechanism, involving fluvial and aeolian processes. Inferred westerly and southwesterly wind directions, as dominant carriers of the aeolian deposits, are in agreement with westerly palaeowind simulations using climate models. However, the role played by westerly tropospheric winds and northerly winds remains to be established.
Article
Beach ridges, frequent components of Quaternary coastal plains, and other coastal landforms, have been cited as indicators of the positions of ancient seashores and associated sea levels. Numerous authors utilized the term beach ridge for active and relict, usually wave-built supratidal and/or intertidal forms. Wind-built ridges have been only occasionally included in the definition. The term was applied also to submerged, landward-shifting, eventually stranded bars. A consistent redefinition of the term is highly desirable. Beach ridges should include all relict strandplain ridges, whether dominated by wave/swash-built or by eolian lithosomes. All active ridge-like shore features, regardless of dimensions, morphology, and origin are excluded. Because of the resistance of coarse-clastic ridges to wave and wind erosion, swash-built gravel or coarse shell (“storm”) ridges may build several meters above the level of high tide. Swash-built high berms, even on pure sandy beaches, exceed the highest tides during episodes of wind-induced, record water levels. Frequently but not always burying underlying low-relief “berm ridges” of berm lithosomes, sequences of relatively steep multiple foredunes are commonly named beach ridge plains. The narrow, subparallel relict foredunes that form these strandplains presently are designated as eolian beach ridges. Beach ridges, thus, are defined as relict, semiparallel, multiple wave- and wind-built landforms that originated in the inter- and supratidal zones. Until separated from the shoreline by progradation, sandy, pebbly or shell-enriched backshore berm ridges behind an active foreshore should not be considered beach ridges. Strandplain progradation is either continuous or, with the inclusion of subtidal (“cat's eye”) ponds, discontinuous. Contrary to claims, transgressive cheniers do not represent “true cheniers” alone; within their overall progradational context, cheniers, a special category of beach ridges bracketed by subtidal–intertidal mudflats, may be transgressive or regressive in character. Landward-driven, transgressive ridges should be designated beach ridges only after they are stabilized on intertidal flats. When recognizable between clearly identifiable intertidal and overlying eolian intervals, the horizontal interface between these lithosomes in beach ridges may help the reconstruction of ancient tide/lake levels. Diagnostic sedimentary textures, structures, and fossils, however, often may be unavailable in the deposits. Along with various types of elevated terraces composed of raised marine deposits and certain coastal landforms of erosional origin that occur worldwide, beach ridges of clearly proven wave-built origin may also serve as indicators of ancient higher-than-present sea levels.
Holocene relative sea-level changes in Uruguay coast. Book of abstracts, Shallow Lakes Congress
  • R Bracco
  • F García-Rodríguez
  • L Del Puerto
  • H Inda
  • C Castiñeira
  • P Sprechmann
Bracco, R., García-Rodríguez, F., del Puerto, L., Inda, H., Castiñeira, C., Sprechmann, P., 2008. Holocene relative sea-level changes in Uruguay coast. Book of abstracts, Shallow Lakes Congress 2008. 75 Poster.
Sítios de Pesca Lacustre em Rio Grande, RS, Brasil. Instituto Anchietano de Pesquisas
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Schmitz, P.I., 1976. Sítios de Pesca Lacustre em Rio Grande, RS, Brasil. Instituto Anchietano de Pesquisas, Unisinos, São Leopoldo (Tese de Livre Docência).
also presented an explanation about the frequency of such deposits in the Lower Uruguay River, Rio de la Plata Estuary and littoral lagoons, which describes them as sand beach ridges with coarse to fine sand on some modally low energy beaches (open coast, lagoon or estuary
  • Moreover
  • Hesp
Moreover, Hesp et al. (2005) also presented an explanation about the frequency of such deposits in the Lower Uruguay River, Rio de la Plata Estuary and littoral lagoons, which describes them as sand beach ridges with coarse to fine sand on some modally low energy beaches (open coast, lagoon or estuary) (Fig. 2).
The beach backshore and beyond
  • P A Hesp
Hesp, P.A., 1999. The beach backshore and beyond. In: Short, A.D. (Ed.), Handbook of Beach and Shoreface Morphodynamics. John Wiley, New York, pp. 145-170.
Las Variaciones del Nivel del Mar y el Desarrollo de las Culturas Prehistóricas del Uruguay
  • R Bracco
  • C Ures
Bracco, R., Ures, C., 1998. Las Variaciones del Nivel del Mar y el Desarrollo de las Culturas Prehistóricas del Uruguay. Rev. Mus. Arqueol. Etnol. 8, 109-115.
The vast majority of the deposits that were sampled and dated by us — which were redefined by Martínez and Rojas (2013) as storm deposits or permanent berms — were recognized as beach ridges (Bracco and Ures, 1998: Table 1; Bracco et al., 2011a: Table 1) According to
  • Secondly
  • Rojas Martínez
  • Hesp
Secondly, Martínez and Rojas (2013) misinterpreted the nature and origin of deposits. The vast majority of the deposits that were sampled and dated by us — which were redefined by Martínez and Rojas (2013) as storm deposits or permanent berms — were recognized as beach ridges (Bracco and Ures, 1998: Table 1; Bracco et al., 2011a: Table 1). According to Hesp et al. (2005) such deposits are sand beach ridges on some modality of low beach (open coast, lagoon or estuary).
Desde su Dimensión Temporal. Costa Atlántica del Uruguay
  • R Bracco
Bracco, R., 2003. Aproximación al Registro Arqueológico del Sitio La Esmeralda ("conchero"), Desde su Dimensión Temporal. Costa Atlántica del Uruguay. Anales de Arqueología y Etnología, N54-55 (1999-2000). Universidad Nacional de Cuyo. Facultad de Filosofía y Letras, Inst. de Arqueología y Etnología, Mendoza, Argentina 13-28.
Reconstrucción Paleoclimática y Paleoambiental para el Pleistoceno Tardío/Holoceno en el Sudeste del Uruguay: aporte del análisis de silicofitolitos. Tesis de Maestría PEDECIBA-Biología-Ecología
  • L Del Puerto
del Puerto, L., 2009. Reconstrucción Paleoclimática y Paleoambiental para el Pleistoceno Tardío/Holoceno en el Sudeste del Uruguay: aporte del análisis de silicofitolitos. Tesis de Maestría PEDECIBA-Biología-Ecología, Facultad de Ciencias.Universidad de la República, Uruguay.
Holocene. Encyclopaedia Britannica
  • R W Fairbridge
Fairbridge, R.W., 1974. Holocene. Encyclopaedia Britannica, pp. 998-1007.