Paleogeographic Models Research Articles

Axial and transverse river deposits preserved in an Aptian rift basin, Northeastern Brazil: Implications for sandstone reservoir quality

A syn-rift, up to 250 m thick, fluvial sandstone unit of Aptian age (Marizal Formation, Tucano Basin, northeastern Brazil) preserves the deposits of an axial fluvial system and contemporary tributaries. These deposits exhibit characteristic variations in composition, grain size, and paleocurrents, indicating different sources for each system. There is a systematic downstream increase in the tributary contribution to the axial system along the basin axis. This sediment mixture model is established based on extensive paleocurrent data in conjunction with macroscopic, microscopic, and detrital zircon provenance data. The spatial distribution of diagenetic patterns and reservoir permo-porosity properties were compared to the paleogeographic model. The comparison revealed that the increase in lithic fragments brought by a main tributary led to a reduction in intergranular porosity and permeability of axial system deposits downstream, following a change in pebble and sand composition. Our findings highlight that the relative amount of bedload brought by tributaries plays a crucial role in the composition and diagenetic evolution of fluvial reservoirs. Spatial variations in sandstone composition at specific stratigraphic intervals are expected due to the intricate patterns of mixture and preservation of axial and transverse river deposits within fault-bounded basins.

Chemostratigraphy and mineralogical characterization of Piacenzian sapropels cluster A (2.75–2.57 Ma) in the Gelasian GSSP type-section of Monte San Nicola (Sicily, Italy): Paleoenvironmental and paleogeographic implications

Mineralogical, geochemical and stable isotope (δ18O, δ13C) data from Marine Isotope Stages (MIS) G4 to 103 are here presented. The studied interval includes the sapropelic cluster A (A2-A5) from the Gelasian GSSP type-section, outcropping at Monte San Nicola (Sicily, Italy). The studied section exhibits a good response of the δ18O measured on the bulk carbonate to the Earth's astronomical parameters. The sapropelic red/brown layers (A2- A5) are alternated to grey marls and this cyclicity is clearly evident by the difference in colour, organic matter content, redox-sensitive elements and runoff indicators, tied to the precession/insolation cycles. Further, the obliquity signal is well evident in paleoproductivity indicators and mineralogical composition, driven by glacial-interglacial cycles. The obtained dataset has allowed the reconstruction of the paleoenvironmental conditions during marls/sapropels deposition, which appears to be influenced by the precessional forcing that induced strong changes in the marine water circulation. This scenario is also integrated by an original paleogeographic model including the presence of a high topographic structure in SE Sicily that limited water exchanges between the Ionian and Central Mediterranean Seas during sea level drawdowns, caused by glacial phases, triggered by obliquity minima.

Phylogenetic biogeography inference using dynamic paleogeography models and explicit geographic ranges.

To model distribution ranges, the most popular methods of phylogenetic biogeography divide Earth into a handful of predefined areas. Other methods use explicit geographic ranges, but unfortunately, these methods assume a static Earth, ignoring the effects of plate tectonics and the changes in the landscape. To address this limitation, I propose a method that uses explicit geographic ranges and incorporates a plate motion model and a paleolandscape model directly derived from the models used by geologists in their tectonic and paleogeographic reconstructions. The underlying geographic model is a high-resolution pixelation of a spherical Earth. Biogeographic inference is based on diffusion, approximates the effects of the landscape, uses a time-stratified model to take into account the geographic changes, and directly integrates over all probable histories. By using a simplified stochastic mapping algorithm, it is possible to infer the ancestral locations as well as the distance traveled by the ancestral lineages. For illustration, I applied the method to an empirical phylogeny of the Sapindaceae plants. This example shows that methods based on explicit geographic data, coupled with high-resolution paleogeographic models, can provide detailed reconstructions of the ancestral areas but also include inferences about the probable dispersal paths and diffusion speed across the taxon history. The method is implemented in the program PhyGeo.

Palynology of the Albian–Turonian sediments from the Sumbe region, Kwanza Basin (Angola): Implications for paleoenvironment, paleoclimate, and paleogeography

Palynological investigations in the Sumbe region of the Kwanza Basin, Angola, have identified Albian to Turonian assemblages in four sections of the Quissonde Facies of the Mucanzo, Cabo Ledo, and Itombe formations. These studies aimed to determine their biostratigraphic ages and infer paleoenvironmental, paleoclimatic, and paleogeographic models. The presence of Odontochitina costata, Palaeohystrichophora infusorioides, and Xiphophoridium alatum cysts supports an upper Albian to lower Cenomanian age for the Mucanzo Formation. Litosphaeridium siphoniphorum cyst and the Elateroplicites africaensis pollen found In the Cabo Ledo Formation suggest a Cenomanian age, while Conosphaeridium striatoconum, Heterosphaeridium difficile, and Dinogymnium acuminatum supports a Turonian age for the lower part of the Itombe Formation. All samples predominantly contain fluorescent amorphous organic matter (AOM) derived from phytoplankton degradation, with increasing AOM in the uppermost units, indicating inner neritic marine deposition under dysoxic-anoxic conditions. During the Lower to mid-Cretaceous, the Gondwana breakup caused significant changes, with the palynological indicating a Tethyan affinity with some high-latitude taxa, suggesting a cosmopolitan distribution. The subtropical to tropical nature of the assemblages, along with high-latitude species, indicates a mid-Cretaceous water connection between the Central Atlantic and the South Atlantic oceans, extending to the Kwanza Basin.

Problemy ophiolitów Zagros i ciał bazaltowych, przykłady z Regionu Kurdystanu, północny Irak

In the Iraqi Zagros, there are ten ophiolites and basaltic bodies, the famous ones are Penjween, Mawat, Bulfat and Peshashan Ophiolite complexes in addition to basaltic bodies such as Kata Rash, Avroman, Gercus, Chalki, and Hamrin basaltic bodies. The present study describes more than 12 significant problems concerning the previous assigning of the bodies as igneous rocks. These problems are observable in the field, laboratory, and in most previous works of literature that oppose the magmatic origin of these bodies. Our study explicated all aspects of each problem and clarified how the problems contradict magmatic crystallization and aid the sedimentary origin of these claimed igneous bodies. Finally, the interpretations of all the problems were collected as conjugate pieces of evidence for appraisal of the new origin of all igneous bodies in the Iraqi and Iranian Zagros belt. The outcomes consider the ophiolitic and basaltic rocks metamorphosed volcaniclastic sandstones (greywackes or mafic sandstone). These sandstones belong to fresh or metamorphosed greywackes of stratigraphic units of the Paleocene-Eocene Walash Formation (as distal facies) and Kata Rash Conglomerate (as proximal facies) which were previously considered volcanic rocks. These sediments are sourced originally from Urumeiah-Dokhtur Magmatic Arc (ADMA) and deposited inside Neo-Tethys, present Sanandaji-Sirjan Zone (SSZ), during the Jurassic-Early Cretaceous. Later, the sediments were metamorphosed and uplifted during the Paleocene and deposited inside the Iraqi Zagros belt by turbidity currents inside the Zagros Foreland basin. These ideas are shown in detail by tectonic and paleogeographic models.

The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S

AbstractThe early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi‐method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U‐Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.

Salt-rich versus salt-poor structural scenarios in the central Northern Calcareous Alps: implications for the Hallstatt facies and early Alpine tectonic evolution (Eastern Alps, Austria)

One of the most remarkable features of the central Northern Calcareous Alps (Eastern Alps, Austria) is the widespread presence of Upper Triassic deep-water carbonates (the Hallstatt facies) and Permo-Triassic evaporites resting on deep-water Middle Jurassic strata and their underlying Upper Triassic shallow-water carbonate platform successions. The Hallstatt facies and accompanying evaporites have been classically interpreted to originate either from a location south of the time-equivalent carbonate platforms, or to have been deposited in deeper water seaways within the broad platform domain. To date, this dispute has been addressed mostly through the analysis of Triassic and Jurassic facies distribution in map view, which, however, is subject to some degree of ambiguity and subjectivity. In this contribution we present, for the first time, sequentially restored regional cross-sections through the central Northern Calcareous Alps to understand the implications of the contrasting paleogeographic models. We present (a) an interpretation based on a highly allochthonous origin of the Triassic deep-water units and (b) an interpretation based on their relative autochthony in which we incorporate the potential influence of salt tectonics in the central NCA. The restored cross-sections provide a framework within which the alternative scenarios and their paleogeographic implications can be better understood. Through this analysis we propose that salt tectonics in the central NCA can provide a valid explanation for apparent inconsistencies in the relative autochthony scenario and thus constitutes a reasonable alternative to the currently accepted allochthony scenario.Graphical abstract

A new reconstruction of Phanerozoic Earth evolution: Toward a big-data approach to global paleogeography

Reliable reconstruction of global paleogeography through deep geologic time provides a key surface boundary condition for investigating many first-order Earth system and geodynamic processes such as climate change, geomagnetic field stability, regional geological and tectonic history, and biological evolution. Over the past decade, the development of the GPlates software led to a resurgence of community efforts in creating state-of-the-art plate tectonic models that integrate paleomagnetic, geological, and paleontological datasets, resulting in a plethora of reconstruction models. In this paper, we briefly review the strengths and weaknesses of existing global models, which depict alternative and sometimes contradictory tectonic scenarios. We then provide an overview of the general procedure in our construction of a revised Phanerozoic global paleogeographic model, including (1) evaluation of the paleomagnetic data that quantitatively dictate continental paleolatitudes and orientations, (2) selection of reference frames in which continents were positioned, and (3) calibration of continental longitudes in deep time. We update the apparent polar wander paths (APWPs) of the major continents using a recently developed weighted running mean approach, which rectifies two major issues with the conventional running mean approach regarding missing paleopoles in age windows and the enforced assumption of the Fisherian distribution. We re-evaluate the Phanerozoic continental reconstructions in a paleomagnetic framework using the updated APWPs, and calibrate continental paleolongitudes following the extended orthoversion hypothesis by placing the centroids of supercontinents Rodinia and Pangea 90° apart, with that of Rodinia at ∼90°E. We emphasize that the resulting global model is not intended to provide solutions to all global tectonic issues throughout the entire Phanerozoic Eon. Rather, we present our results as one viable model of Phanerozoic tectonic history which, like many existing interpretations, is built upon our understanding of the paleomagnetic, geological, and paleontological observations. Our goals are for this study to highlight the fundamental differences between reconstruction models and to serve as a starting point for future studies to fill key data gaps and test alternative hypotheses and tectonic scenarios.

Paleontology, Stratigraphy and Biogeography of the Late Precambrian and Phanerozoic Formations of Russia

Abstract —This special issue is dedicated to discussing the possibility of the stage division of the Vendian system, specifically, a composite section of the Siberian Platform is proposed as a stratigraphic standard. For the Ordovician system of the Siberian Platform and Northeastern Russia, certain changes in stratigraphic charts are proposed, nomenclative issues and different variants of correlations of regional horizons with the General Stratigraphic Scale (GSS) of Russia are considered. A geochemical analysis of Bajocian and Bathonian belemnite rostra of Arctic Siberia was carried out and for the first time a comprehensive C, O, and Sr isotope characterization of the sections was obtained, making it possible to propose a comparison of the studied sections with the European standard and to develop paleogeographic models. Comprehensive studies of the Upper Jurassic and Lower Cretaceous series of the Anabar Bay deposits (Laptev Sea) led to an improved biostratigraphic division for this reference section and to the identification of the levels for interregional and global correlation. The magnetostratigraphic division of the Jurassic–Cretaceous boundary interval and its comparison with the Tethyan regions are discussed. Taking into account biostratigraphic data, the δ13Corg variation curve can also serve as a correlation tool. The clinoform structure of Upper Jurassic strata was revealed in the northwest of the Anabar–Khatanga depression, based on the interpretation of seismic profiles calibrated against studied sections. The formation of this complex allows us to consider this stage as the initiation of the Verkhoyan orogeny in this folded area. Analysis of variations in the thickness of sediments allows us to deduce that intense tectonic-sedimentary processes took place during the Late Jurassic epoch, along with subsidence of the bed of the sedimentary basin. Analysis of a specific assemblage of lacustrine fossils from the reference section of the upper part of the Lower Cretaceous series of Transbaikalia and of published data showed that this fossil assemblage was widespread in East Asia. Biofacies analysis made it possible to reconstruct the paleoenvironments of this time.

Geochemistry of metasedimentary rocks from the Eastern Pyrenees (Iberian Peninsula): Implications for correlation of Ediacaran terranes along the Gondwanan margin

The North African margin of Gondwana formed by subduction and accretion during Ediacaran to Cambrian times. Sections of this active margin were incorporated during the late Paleozoic to the Variscan and Appalachian orogens. In the Variscan realm, these sections define in some regions a Cadomian basement comprising thick metasedimentary series associated with coeval subduction-related magmatic rock dated in the range 650–500 Ma. In the Cap de Creus Massif (Eastern Pyrenean domain), the Cadomian metasedimentary rocks formed from sediments derived from mixed felsic and intermediate/mafic sources, intruded by granitoid and minor mafic igneous rocks. These series were formed in a peri-Gondwanan volcanic arc setting, like other Cadomian series described in the SW of the Iberian Massif, such as Serie Negra Group of the Ossa Morena Complex. However, the Nd model ages of the Cap de Creus metasedimentary samples range from 1431 to 1620 Ma and are younger than those of their SW Iberia equivalents. This result can be interpreted as an indication of an eastern location in the Ediacaran - Cambrian peri-Gondwanan magmatic arc. Furthermore, the Cadomian series in the Central Iberian Zone have even younger Nd model ages than those of SW and NE Iberia. We present two end-member paleogeographic models consistent with reconstruction of the initial location of the Cap de Creus Massif and its relations with other domains (Ossa Morena Complex and Central Iberian Zone) in this sector of the North African Gondwanan margin.

Strengthening the argument for a large Greater India

The Sangdanlin section in southern Tibet represents a geologic Rosetta stone to constrain the initiation of the India-Asia collision from its sedimentary and paleomagnetic records. However, geoscientists have arrived at fundamentally divergent interpretations surrounding the age of the strata and its paleomagnetic record. Here, we report paleontologic, petrographic, and paleomagnetic data from the Sangdanlin section that recognize the sequence as a thrust complex containing interlaced Barremian-Albian (Early Cretaceous) and Paleocene strata, each separated by thrust faults. Recognizing two complexly interwoven formations of distinctly different ages contradicts a continuous stratigraphic superposition. Assigning an Early Cretaceous, instead of Paleocene, age to the units collected for paleomagnetic data revises paleogeographic models thereby supporting a large (2,000 to 3,000 km) extent of Greater India, with collision initiating at 55 ± 5 Ma in the western Himalayas. A contiguous plate in the Neotethys Ocean precludes that Asia's southern margin was built through a succession of accreted terrains.

Drainage and sedimentary response of the Northern Andes and the Pebas system to Miocene strike‐slip tectonics: A source to sink study of the Magdalena Basin

AbstractMiocene strike‐slip tectonics was responsible for creating and closing short‐lived (ca. 6 Ma) passages and the emergence of isolated topography in the Northern Andes. These geological events likely influenced the migration and/or isolation of biological populations. To better understand the paleogeography of the Miocene hinterland and foreland regions in the Northern Andes, we conducted a source‐to‐sink approach in the Magdalena Basin. This basin is located between the Central and Eastern Cordilleras of Colombia and contains an ample Miocene record, which includes Lower Miocene fine‐grained strata and Middle Miocene to Pliocene coarsening‐up strata. Our study presents a new data set that includes detrital U–Pb zircon ages (15 samples), sandstone petrography (45 samples) and low‐temperature thermochronology from the Southern Central Cordillera (19 dates); which together with previously published data were used to construct a paleogeographical model of the Miocene hinterland and foreland regions in the Northern Andes. The evolution of the Magdalena Basin during the Miocene was characterized by playa and permanent lake systems at ca. 17.5 Ma, which may be related to a marine incursion into NW South America and western Amazonia. The appearance of Eocene to Miocene volcanic sources in the Honda Group after ca. 16 Ma suggests the development of fluvial passages, which connected the Pacific with the western Amazonia and Caribbean regions. These passages were synchronous with a time of Miocene exhumation and topographic growth (ca. 16 to 10 Ma) in the Central Cordillera and the transition from lacustrine to fluvial deposition in the Magdalena Basin. Middle to Late Miocene strike‐slip deformation promoted by oblique plate convergence and the oblique collision of the Panamá‐Chocó Block likely explains the synchronous along‐strike fragmentation and exhumation in the Central Cordillera.

Caspian transgressive-regressive cycles across the Lower Volga region during the Quaternary reconstructed from the borehole at Ulan-Khol (Kalmykia, Russia)

During the Quaternary, the Lower Volga region was typically a shallow shelf of the Caspian Sea. This region regularly and distinctively responded to sea level fluctuations by changing both sediments and biota. This region is therefore a key to understanding the history of the transgressive-regressive cycles of the Caspian Sea during the Quaternary. There is a wealth of information about the Quaternary deposits of the Lower Volga region; however, their diversity of facies, erosional processes, and fragmented sections create difficulties in stratigraphic interpretation and the development of paleogeographic models. The studied 500-m section of borehole 8 Ulan-Khol is among the few in the Caspian region that allows for the sequential reconstruction of the Quaternary history of the region in one section. These borehole data offer a unique opportunity to reconstruct transgressive-regressive cycles in Pleistocene basins located in the most southeastern part of Europe (the Caspian region). Based on biostratigraphic, sedimentological, and paleomagnetic methods, we were able to define main Early, Middle, and Late Pleistocene units, which were correlated with regional stratigraphical units. Each unit corresponds to regional paleogeographic events and sedimentation modes characterized either by basinal (brackish water) or continental conditions when lagoons and fluvial landscapes dominated. The borehole interpretation integrated with regional data demonstrates a complex history of Caspian basin development during Apsheronian time (MIS 63–20) with the presence of a strong regression in its final stage, accompanied by a previously unknown advance of the Paleo-Volga valley to the latitude of Astrakhan city and further south. This regression and the formation of the Paleo-Volga valley continued during Tyurkyanian time (MIS 19). By the end of the Tyurkyanian, the regression was followed by a transgressive stage, which culminated in Bakunian time (MIS 18–12). The Khazarian stage (MIS 11–5) of Caspian Sea development was characterized by a constant change from alluvial-marine to marine and estuarine environments. The borehole data support our earlier conclusion that the Singilian deposits separate the lower (MIS 11–7) and upper (MIS 5) Khazarian units. New data support the existence of only one transgression of the Caspian Sea during Khvalynian time (MIS 3–2); after its maximum stage the sea level gradually decreased with the formation of coastlines at several terrace levels. Due to its high deposit thickness and rich paleontological, stratigraphic and lithological information, Ulan-Khol borehole 8 can be considered a key site for the Northern Caspian area.

Characterization and stratigraphic review of the upper Jurassic – Lower Cretaceous Mendoza Group in the Blanco river valley (∼33°SL)

The Jurassic-Cretaceous Mendoza Group is one of the most distinctive lithostratigraphic units of the widely surveyed Neuquén basin. This work focuses on its development in the Aconcagua basin, which crops out at the Aconcagua fold-and-thrust belt in the Principal Cordillera, and contrasts with its evolution in the main Neuquén basin by remarkable differences. By logging a series of stratigraphic sections, we performed a detailed revision of the Mendoza Group's stratigraphy and contact relations along the Blanco River valley (∼33°S). We reassigned several outcrops to the Mendoza Group based on our field observations and recent research, updating the current geological map of the study area. We identified an irregular development of the lower contact relation with the Auquilco Formation that denotes the existence of a paleo-topography at the time of deposition of the upper beds of the Mendoza Group. Moreover, we dismissed previous proposals of a lateral interfingering relation with the Juncal Formation, and in place, we describe an angular unconformity with an overlying Upper Miocene volcanic unit. Additional insight from the redefinition of the upper contact is brought by the characterization of an erosive surface at the top of the Mendoza Group, and the identification of a period of subaerial platform exposition and erosion. A previous paleogeographical model shows a good fit with the observed facies along the Blanco River valley and can be extended towards southern latitudes. Differences in the development of the Mendoza Group in the Aconcagua basin and the main Neuquén basin have been acknowledged, and a potential origin of this unusual behavior has been explored in the reactivation of an Early Jurassic structural high.

Geology of recently recognized lithologies inside the Red Bed Series in the Chwarta-Mawat area, Kurdistan Region, NE-Iraq

The sequence of the coastal siliciclastic facies of the Paleocene-Eocene Zagros Foreland Basin is well exposed in the Chwarta-Mawat area, north of Sulaimani Governorate, northeastern Iraq. According to previous studies, this sequence is designated as Red Beds Series (RBS), consisting of more than 2000 m of fine and coarse red and grey clastics. The present study found recently recognized lithologies (RRLs) about 100 thick inside the series and encompassed green marlstone with subsidiary detrital limestone which has significant tectonic and paleogeographic results. The petrography, biostratigraphy, and boundary conditions studies are applied to uncover their origin. The new lithologies are deposited in the subsiding basin in the Imbricate Zone during the Middle Eocene. During this age, the Tertiary Foreland Basin was separated by a paleohigh into two basins, (northern and southern basins). In the northern basin, the RRLs have deposited as deep facies of the Naopurdan Formation while in the southern basin the Pila Spi Formation was deposited as lagoonal facies. The former formation was deposited as reefal facies in the shelf area of the northern basin to the northeast Chawrta and Mawat Towns. The RRLs, units one and two of the series (in the Thrust Zone) are correlated respectively with Pila Spi, Sinjar and Gercus formations in the High Folded Zone. These correlations are shown on the stratigraphic columns and paleogeographic models with the aid of nannofossil and benthonic foraminiferal studies. This study is the most important step for solving the tectonic and paleogeographic setting of northeastern Iraq and for a better understanding of the Zagros Collisional belt.

Genesis of a coastal aquifer in the coastal plain of the Pelotas Basin, southern Brazil: Implications for stratigraphic evolution

In the coastal plain of the Pelotas Basin, southernmost Brazil, a granular aquifer close to 70 m deep, formed by coarse and angular sediments, caught the attention of drillers, who gave it the suggestive nickname of “Coarse Salt” (“Sal Grosso”). Despite being almost unknown in geological and stratigraphic terms, the aquifer has been increasingly used to supply the growing coastal population. Considering that stratigraphic knowledge is essential for the management of groundwater resources, we sought to understand the configuration of this aquifer and investigate its genesis based on drilling samples from 29 groundwater wells and through 19 vertical electrical soundings. The sedimentary record investigated has an approximate thickness of 100 m, and is formed by three units, interpreted as: alluvial (where the aquifer is located), marine and coastal barriers. The analysis of the sediments that make up the Coarse Salt (Sal Grosso) aquifer led to the interpretation that the investigated region represents the distal (fluvial) portion of an alluvial system. Spatially, the aquifer constitutes an elongated feature in the NW-SE direction, perpendicular to the current coastline. The geometry and sedimentology led to the interpretation of a paleochannel, responsible for the transport of sediments from the granitoid rocks of the Sul-Riograndense Shield, associated with the paleodrainage system of the Jacuí River. A greater stratigraphic variability present in wells closer to the continent, with intercalation of continental and marine deposits, indicated the position of a coastline, prior to the formation of the coastal barrier unit, which is the predominant depositional system in the actual coastal plain. The stratigraphic analysis resulted in the paleogeographic model corresponding to a complete depositional sequence, indicating that the Coarse Salt (Sal Grosso) aquifer was formed during a lowstand. Later, a marine transgression allowed the deposition of a thick bundle of muddy sediments, which constitutes an important protection to the aquifer. Afterwards, the coastline started to prograde, with the development of the barrier-lagoon systems in a highstand/falling stage systems tracts context. The understanding of stratigraphy generates framework for decision-making that enable better management of this groundwater resource.

Organic geochemical evidence for the transition of Aptian-Albian hypersaline environments into marine restricted seas: The South Atlantic oceanic northern gateway and its implications for the pre-salt deposits

The transition between Aptian and Albian stages of the Lower Cretaceous (∼113 Ma) was a critical moment in the development of the proto–South Atlantic Ocean. At this time, marine ingressions in Brazilian sedimentary basins occurred in the northeastern region and deposited organic-rich mudstones and sulfate evaporites. However, the paleogeographic configuration that controlled sedimentation and biota dynamics remains poorly understood. This study presents new paleogeographic insights based on tectonic reconstructed Gplate models and a high-resolution chemostratigraphic framework. We explore new isotopic data of bulk organic carbon and nitrogen as well as saturated fraction biomarkers collected from a well-preserved section in the eastern part of the Brazilian northeastern Parnaíba Basin (Codó Formation). We also present new biomarker data for samples from the Barra Velha Formation from a well in the Santos Basin, which belongs to the same local stage of the Codó Formation (Alagoas Stage). For the Parnaíba Basin section, geochemical proxies subdivide the environmental evolution into five stages. These stages reflect a transition from a highly saline environment (stage A) that experienced transient marine influxes and eventually transitioned into a closed evaporitic system (stage B). A major marine ingression established an epicontinental anoxic sea (Stage C) that subsequently experienced an increase in water circulation and water depth; turning into an oxic marine environment (Stage D). Interruption of the connection with the sea and constant terrestrial input led to a continentalization process establishing a lacustrine/continental environment (Stage E). For the Santos Basin section (Barra Velha Formation), we measured the occurrence of the C30 tetracyclic polyprenoids which are consistent with a dominant lacustrine saline environment. Our paleogeographic model suggests that marine ingressions towards the southern basins, during the first stages of Pangea breakup, occurred through the northern portion of the Borborema Province and produced an interior seaway that possibly connected the Brazilian northeastern with the southeastern basins through the Recôncavo/Tucano rift system. Our findings and the environmental interpretations for stratigraphic correlated units from the southern continental basins infers that the greater marine influence in the northeastern areas shifted from hypersaline environments into restricted marine environments that resulted in the deposition of shales and mesohaline/penesaline salts. Concomitantly, the existence of a Brazilian-African landbridge acted as a barrier point for the first marine inflows towards the south. The restricted marine connection transformed south alkaline environments into extensive areas of superhaline conditions that resulted in giant thick salt successions of the South Atlantic basins. Finally, further tectonic evolution and complete breakup of Pangea terminated the Brazilian-African landbridge and shutoff interior marine routes that later became terrestrial environments. As the continents steadily became rifted-segments, the proto-South Atlantic Ocean expanded leaving a marine record in the southern basins.

Cenozoic Tethyan changes dominated Eurasian animal evolution and diversity patterns.

Cenozoic tectonic evolution in the Tethyan region has greatly changed the landforms and environment of Eurasia, driving the evolution of animals and greatly affecting the diversity patterns of Eurasian animals. By combining the latest Tethyan paleogeographic models and some recently published Eurasian zoological studies, we systematically summarize how tectonic evolution in the Tethyan region has influenced the evolution and diversity patterns of Eurasian animals. The convergence of continental plates, closure of Tethys Sea, and Tethyan sea-level changes have directly affected the composition and spatial distribution of Eurasian animal diversity. The topographic and environmental changes caused by Tethyan tectonics have determined regional animal diversity in Eurasia by influencing animal origin, dispersal, preservation, diversification, and extinction. The ecological transformations resulted in the emergence of new habitats and niches, which promoted animal adaptive evolution, specialization, speciation, and expansion. We highlight that the Cenozoic tectonic evolution of the Tethyan region has been responsible for much of the alteration in Eurasian animal distribution and has been an essential force in shaping organic evolution. Furthermore, we generalize a general pattern that Tethyan geological events are linked with Eurasian animal evolution and diversity dynamics.

Submerged landscape evolution of the Beagle Channel: context of the first record of underwater archaeological evidence

ABSTRACT We analyze the finding of a lithic projectile point at more than 100 meters depth in the Beagle Channel (Tierra del Fuego, Argentina) in relation to submerged landscapes. On the one hand, this underwater evidence is examined as part of an inundated archaeological landscape supporting the hypothesized Pleistocene coastal dispersion in southern South America. On the other hand, the lithic projectile point is evaluated as a submerged isolated artefact as the result of human movements through aquatic environments due to foraging and transport practices in the sea during the Holocene. Technological properties and post-depositional modifications of the projectile point are described, and the artefact location is assessed in light of paleogeographic models. The presented evidence does not support an early human occupation in the region, but the particular archaeological detection offers insights to the alternative explanation, and to the potential of underwater explorations in the region.

Comments on “Devonian to Permian post-orogenic denudation of the Brasília Belt of West Gondwana: Insights from apatite fission track thermochronology” by Fonseca et al. (2020)

In a recent paper published in the Journal of Geodynamics (vol. 137, June 2020, 101733), Fonseca et al. (2020) proposed a thought-provoking model aiming to elucidate the exhumation history of the Neoproterozoic Brasília Fold Belt (BFB) between the Devonian and Cretaceous periods. Exclusively based on information from the literature and new thermochronological data, Fonseca et al. (2020) presented an alternative model that tries to bind tectonic uplift, erosion, and the influx of clastic material coming from the BFB into the intracratonic Paraná Basin. Although the welcome proposal and reliable quality of the analytical data, the hypothesis presented diverges from several previously published works. In the light of the presented apatite fission-track ages, we disagree with their paleogeographical model, which puts the Brasília Fold Belt as a major source for clastic detritus to the Paraná Basin between the Devonian to Permian. The primary goal of our comments is to clarify the state-of-art of the intricate source-to-sink system of the Paraná Basin. Secondarily, we try to demonstrate why the model proposed by Fonseca et al. (2020) presents some geodynamic and interpretative problems and do not characterize an adequate paleogeographic scenario for southwest Gondwana between the Devonian to Permian periods.