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Micropalaeontological studies of borehole cores 1AS-7D-AM and 1AS-8-AM, from Atalaia do Norte, Amazonas state, Brazil, support previous evidence for Miocene marine ingressions in Western Amazonia. Three marine incursion events are recorded: the first in the Early/early Middle Miocene (in both cores), the second in the late Middle/early Late Miocene (1AS-8-AM), and the third in the Late Miocene (1AS-7D-AM). The first event is characterized by exclusively mangrove taxa, and the last two present a mixture of marine, fresh, and brackish water taxa. However, at the end of the third event an increase of fluvial influence is demonstrated by the predominance of freshwater taxa. These marine incursions reached the study area through narrow and geographically limited connections, controlled by the tectonic setting, at a time between the Early/early Middle Miocene and late Middle/Late Miocene. Thereafter, fluvial conditions were reestablished before Pliocene times. [ABSTRACT FROM AUTHOR]

Discusses the dispute on fishing between the Canada International Court of Justice and Spain. Details on the amendment of the Coastal Fisheries Protection Act of Canada on May 12, 1994; Basis for the optional clause of the act.

Sedimentary carbonate outcrops of the Pirabas Formation at the Bragantina platform in North Brazil represent the exposed portion of the entire carbonate succession in the marine equatorial platform from the subsurface Ilha de Santana Formation (Cretaceous/Maastrichtian-Miocene/Messinian) in the Pará-Maranhão Basin. The transgressive deposits, flooding, and advance of the carbonate platform were investigated through the study of outcrops of the Pirabas Formation (type locality in the Ilha de Fortaleza, Pará state) and the analogous carbonate from the uppermost section of the Ilha de Santana Formation from the well 1-MAS-16-MA (510–660 m below sea floor). The stratigraphic analyses were based on petrography, microCT, microfossil assemblages (foraminifera, ostracods, and bryozoans) and index species (Amphistegina , Archaias , Pyrgo , Quinqueloculina , Pirabasoporella , Nellia , Skylonia , and Alpheus), and biofacies approach. The Ilha de Santana Formation (Burdigalian/Langhian at 510–660 mbsf section of 1-MAS-16-MA) and the Pirabas Formation (Burdigalian at the Ilha de Fortaleza outcrops) suggest that shallow-water sedimentary facies are similar to those deposited in the marginal basins and mark the start of siliciclastic supplies to the inner platform and the decline of coralline algae carbonate factories. • Onshore/offshore carbonate successions Pirabas/Ilha de Santana formations correlate. • Microfossils from both formations indicate shallow, photic zone deposition. • Pirabas outcrops and Ilha de Santana's upper section co-occur in the Burdigalian. [ABSTRACT FROM AUTHOR]

An abstract of the article "Palaeoenvironmental evolution in South-western Amazonia (Brazil) in the Neogene," by Melissa Fonseca and colleagues is presented.

The Bragantina Platform is an onshore basin of the Brazilian equatorial margin, including the Pirabas Formation, the youngest bioclastic-dominated formation in the area (early–middle Miocene), testifying to the final demise of carbonate factories along this margin area and the transition to a siliciclastic-dominated sedimentation. Although the greatest part of the Pirabas Formation is overlain by the Barreiras Formation and the post-Barreiras deposits, the outcrops provide the opportunity to investigate these Neogene successions that are the onshore equivalent of the large offshore basins (e.g. Amapá Formation: Foz do Amazonas and Ilha de Santana Formation: Pará-Maranhão) of the margin. The latter are deemed to represent an important target for reservoir models. Aiming to thoroughly describe the Pirabas Formation deposits and provide a quantitative and simple approach to analysing the outcropping successions, this study examines seven different successions and a quarry using palaeontological and petrographical methods. Similar to the modern Brazilian equatorial margin, the siliciclastic fraction in the Pirabas Formation rocks decreases as the distance from the coast increases, whereas the bioclastic material is found in greater amounts offshore. However, while the carbonate production close to the Amazon River mouth currently occurs hundreds of kilometres offshore, the carbonate factories in coastal along the Pirabas platform are also located in coastal waters. This indicates that the terrigenous input over the carbonate rocks was still lower than that found at present. The combining analysis of the skeletal and foraminiferal assemblages enabled a separation of protected embayments (characterised by seagrass-related assemblages), exposed areas (characterised by bioclastic shoals) and mangrove forests (characterised by dark fine-grained sediments). This accurate approach serves as an unprecedented reference for the northeastern part of the South American equatorial margin and lays the foundation for future research. • The Pirabas platform was characterized by siliciclastics close to the coast and by bioclastics in the distal inner platform. • Bioclastics–dominated distal inner-platform and siliciclastics–dominated proximal inner platform can be recognised. • Mangrove swamp settings characterized portions of the proximal inner platform. [ABSTRACT FROM AUTHOR]

The Western Amazon was affected by tectonic events of great impacts, such as the uplift of the Andes during the Neogene. Such events promoted significant changes in the fluvial drainage system, in the climate, as well as in the ecosystems, triggering great irradiation of the Amazonian biota. Marine evidence recorded in the region also influenced the radiation of the biota. Despite advances in the paleoenvironmental and age models proposed for the Western Amazon deposits, we still observe conflicting results and interpretations on these aspects. Thus, here were analyzed the palynological content of three cores aimed to contribute with new paleoenvironmental and biostratigraphic data of the Solimões Formation. We presented new paleobotanical data from the 1AS-5-AM, 1AS-7D-AM, and 1AS-8-AM cores and correlated the biostratigraphic data already published with the data obtained here; were recognized five palynozones (Verrutricolporites , Psiladiporites , Crassoretitriletes , Grimsdalea , and Asteraceae), reaching a range from the early to the late Miocene. The vegetation throughout the sequences studied includes elements of dryland forest next to zones of wetlands vegetation, including flooded forests and swamps; the floristic composition changed over time, predominating flooding vegetation during the early and part of the middle Miocene. • Vegetation changed during the Miocene in Amazonia. • Flooding vegetation predominates between early and middle Miocene. [ABSTRACT FROM AUTHOR]

The off-shore Cenozoic succession of the Pará-Maranhão Basin of the Brazilian equatorial margin is studied to investigate skeletal and foraminiferal assemblages during the Oligocene-Miocene interval, one of the fundamental moments in the environmental evolution of our planet. The material from core 1-MAS-16-MA is analyzed using a combination of conventional paleontological analyses, and innovative approaches like micro-CT scan and U/Pb dating on carbonates. The results allowed to clearly constrain the Oligocene – Miocene interval and divide it into four foraminiferal assemblages and seven biofacies useful for both paleoenvironmental reconstructions and stratigraphic correlations. The paleoenvironmental analysis indicates a common pattern of relative sea-level oscillations with the nearby Foz do Amazonas Basin, highlighting a common behavior of this part of the equatorial passive margin during the Oligocene – Miocene interval. The comparison between the succession of skeletal and foraminiferal assemblages of the investigated core and other successions of the Southern and Central American area indicated the presence of stratigraphically relevant foraminiferal assemblages that could be useful for improving the correlation between the various Cenozoic successions of the area (assemblages dominated by nummulitids and lepidocyclinids in the Rupelian; assemblages dominated by Heterostegina (Vlerkina) antillea , lepidocyclinids, and primitive miogypsinids in the Chattian; assemblages dominated by Heterostegina (Vlerkina) antillea , lepidocyclinids, and miogypsinids other than Miogypsinoides and Miogypsinella , in the Aquitanian; assemblages dominated by advanced miogypsinids in the Burdigalian; post Early Miocene assemblages characterized by the lack of abundant lepidocyclinids and miogypsinids). Finally, the overall resilience of most of the large benthic foraminifera taxa to the Oligocene – Miocene transition testifies once more to the adaptability of this group of carbonate producers. • 4 foraminiferal assemblages and 7 biofacies were identified using a multi-technique approach. • Amphisteginids, miogypsinids, lepidocylinids, and heterosteginids dominate the foraminiferal assemblage • An Oligocene to the Middle Miocene age is suggested by LBF and U/Pb dating • Correlations are provided with the other Southern and Central American successions, highlighting the resilience of LBF assemblages to the Oligocene-Miocene transition [ABSTRACT FROM AUTHOR]

The Bragantina Platform is an important sedimentary package that occurs in northwestern Brazil, typically around the equatorial western Atlantic coast. Most of the latest Neogene succession of this carbonate-siliciclastic platform consists of the Pirabas Formation of Miocene age (Burdigalian to Serravalian). High-energy coastal storms and hurricanes as a consequence of trade wind anomalies during the Neogene impacted the shallow-water inner marine heterozoan assemblage deposits of the Pirabas Formation. A chaotic overlap of benthic infauna and epifauna, and of demersal and pelagic species in the same section was analyzed using petrography, petrophysics, micro- and macropaleontology, taphonomy, and geochemistry in order to understand sedimentary and paleoenvironmental processes. The equatorial carbonate platform of Brazil reveals high-energy and multiple Miocene tropical storms. This high-energy wave environment caused severe damage to shallow-water heterozoan assemblages at the seafloor, resulting in chaotic faunal arrangements, and removing fine-grained particles thus improving the petrographic properties of the rock (porosity and permeability). • The equatorial carbonate platform of Brazil reveals high-energy and multiple Miocene tropical storms. • MicroCT, paleontology, petrography, porosity, and geochemistry analysis show high accuracy of storm interpretation. • The analysis shows a useful dataset of diagenesis and porosity for the carbonate reservoir model. • The Pirabas Formation carbonate-siliciclastic is an appropriate experimental reservoir model. [ABSTRACT FROM AUTHOR]

The lower Miocene Pirabas Formation in the North of Brazil was deposited under influence of the proto-Amazon River and is characterized by large changes in the ecological niches from the early Miocene onwards. To evaluate these ecological changes, the elasmobranch fauna of the fully marine, carbonate-rich beds was investigated. A diverse fauna with 24 taxa of sharks and rays was identified with the dominant groups being carcharhiniforms and myliobatiforms. This faunal composition is similar to other early Miocene assemblages from the proto-Carribbean bioprovince. However, the Pirabas Formation has unique features compared to the other localities; being the only Neogene fossil fish assemblage described from the Atlantic coast of Tropical Americas. Phosphate oxygen isotope composition of elasmobranch teeth served as proxies for paleotemperatures and paleoecology. The data are compatible with a predominantly tropical marine setting with recognized inshore and offshore habitats with some probable depth preferences (e.g., Aetomylaeus groups). Paleohabitat of taxa particularly found in the Neogene of the Americas (†Carcharhinus ackermannii, †Aetomylaeus cubensis) are estimated to have been principally coastal and shallow waters. Larger variation among the few analyzed modern selachians reflects a larger range for the isotopic composition of recent seawater compared to the early Miocene. This probably links to an increased influence of the Amazon River in the coastal regions during the Holocene. [ABSTRACT FROM AUTHOR]

Several studies have reported Miocene shallow-marine incursions in the Pebas Megawetland system (Western Amazonia) based on paleontological and sedimentological evidence. Only a few publications restricted to Middle and Late Miocene fossils outcropping in the Iquitos (Peru), Benjamin Constant and Eirunepé (Brazil) areas have provided isotopic evidence to test these incursions. In this study, we present new carbon, oxygen, and strontium (87Sr/86Sr ratios) isotopic data of macrofossils (pacu and ray teeth, crab claws and oysters), and microfossils (ostracods and foraminifera) from reported lower to lower upper Miocene sedimentary rocks of Western and Eastern Amazonian (Peru and Brazil), mainly from shallow-marine deposits. It was also analyzed present-day organisms from distinct environments (beach, sea, riverine, and estuary) and compared these results with Miocene fossils. While C and O isotopic compositions indicate that Western Amazonia fossils display an isotopic composition similar to the present-day continental, limnic and riverine, environments (−17‰ to −5.61‰ for δ13C and − 10.14‰ to −1.92‰ for δ18O), Eastern Amazonia fossils display C and O isotopic compositions comparable to those from seawater environments (−2.53‰ to −0.72‰ for δ13C and − 4.85‰ to −1.76‰ for δ18O). We further used the 87Sr/86Sr isotopic composition of the fossils to estimate paleosalinity conditions. The 87Sr/86Sr isotopic compositions indicates that Eastern Amazonian water bodies of the Pirabas Formation (Marajó Basin) varied from mesohaline to marine conditions. In contrast, Early Miocene Western Amazonian water bodies of the Pebas Megawetland System (PMWS) are characterized by freshwater conditions. Nonetheless, in Middle and Early Late Miocene, oligohaline conditions are found in the Peruvian part of the PMWS. Paleosalinity estimates of the Brazilian part of the PMWS are less constrained and might indicate a salinity range between freshwater or oligohaline conditions. Our isotopic data suggest the PMWS was occasionally submitted to oligohaline conditions during Middle and Early Late Miocene shallow-marine incursions. We suggest that Miocene shallow-marine incursions in Western Amazonia at this time were characterized by transitional paleoenvironments, reconciling isotopic, sedimentological and paleontological evidences. • 374 Miocene Amazonian fossils attributed to shallow marine intervals analyzed. • Isotopic analyses of lower Miocene fossils from Eastern Amazonia indicate mesohaline to seawater conditions. • Isotopic data of middle and lower upper Miocene fossils from Peru yields oligohaline conditions in the Pebas Megawetland. • Marine incursions in Western Amazonia studied here occurred in transitional paleoenvironments with low seawater contribution. [ABSTRACT FROM AUTHOR]