Ancient Coastline Research Articles

Short Period Spectral Acceleration Zonation of Tehran a Comparison between Slip and Activity Rates Data’s

This study presents seismic hazard analysis and provides spectral iso acceleration maps based on slip rate (SR) and also activity rate (AR) of the faults. Nowadays modern seismic design of structures is complicated so special attention to the nature of the seismicity in active seismic zones like Tehran is required. Many studies, based on seismic hazard analysis have been done in Tehran. However, none of these studies provided comparison between SR, AR and spectral seismic zonation. In order to reduce the loss of life and property in metropolitan Tehran such studies are undeniable. The process of this study is identification of seismic sources, estimation of seismic parameters and interpretation the results of paleoseismology. Seismic hazard assessment for grid points has been done based on seismic sources and the determination of shear wave velocity. Based on these studies, the shear wave velocity for the upper 30 m has been prepared as a basic parameter for seismic hazard analysis. In addition, iso acceleration spectral maps were prepared based on the SR and AR, for 475 years return period. Referring to paleoseismology studies, it is apparent that some faults in South and South East of Tehran should be considered as an ancient coast line; therefore, they were excluded from the seismic studies. As a result, acceleration in South East Tehran has dramatically declined. In a general comparison, it can be stated that the acceleration based on data from the SR is higher than the AR for the period of 0.4 seconds. The results are equal, in period of 0.4 s and after that the acceleration based on AR is higher than SR.

ANCIENT COAST LINES AND RATES OF ABRASION DURING THE PLEISTOCENE IN THE SOUTHERN AND WESTERN CRIMEA

A series of longitudinal profiles of coastal slope of Southern and Western Crimea have been compiled and analyzed. It revealed the ancient coastlines. Their age have been determined by the regional curves of sea level change. Ancient coastlines helped us to calculate rates of abrasion during last 18 thousand years as well as during all upper and middle Pleistocene. They have been compared with the present real and potential rates of abrasion. In most cases current rates are smaller, however there are some exceptions. The comparison of underwater coastal slope profiles and the rates of abrasion in the Western and Southern Crimea have been made. The rates at the Southern Coast are several times smaller than at the Western Coast.

STRUCTURE AND DYNAMICS OF SEDIMENTATION OF PRODUCTIVE STRATUM BS10-11 IN THE SOUTH-YAGUNSK FIELD

The article presents the analysis of the results of the correlation of sections by twenty-three profiles located across the strike of the ancient coastline along the regression of Neocomian basin, i.e. in the latitudinal direction. The structure and dynamics of sedimentation of the productive stratum BS-10 in the South-Yagunsk field are identified.

Archaeological History of a Fijian Island: Moturiki, Lomaiviti Group

Moturiki is one of the high islands in the Lomaiviti Group, central Fiji. In this article we present exhaustive empirical information on archaeological survey and test pit excavations carried out in 2008 and 2010. An interesting archaeological landscape emerged, with 89 archaeological sites found on Moturiki and neighboring islands Yanuca Levu, Leleuvia, and Caqalai. The sites include ring-ditch villages, terraced villages, isolated house mounds ( yavus ), and burial sites. Results from one of the test pits on the southeast of the island indicate possible landscape changes in the last millennium, since the ancient coastline is currently buried at around 1 m below the surface. This lowland area has therefore received large amounts of sediment from higher areas, a likely result of human activity. We also documented remains from a previously recorded Lapita site in the island. Overall, a shift in the settlement patterns from the coast, to the interior areas, back to the coast, has been documented. This shift, taking place on extremely small islands, can hardly be explained by environmental changes. The article puts together our findings and hypothesis, as well as providing the emphasis of our methodological approach.

The environs of Elaia's ancient open harbour – a reconstruction based on microfaunal evidence

During Hellenistic and Roman times, Elaia, the harbour city of ancient Pergamum, was an important place of trading and traffic. Intense mercantile and military activities are documented by literary sources and archaeological evidences. Geomagnetic and geoelectric investigations detected building structures close to the ancient coastline, which are interpreted as ship sheds. The aim of this study was to reconstruct the coastal evolution, particularly with regard to harbour-related facilities. For that purpose, a 10 m long sediment core was drilled in the area of the ancient open harbour immediately in front of the supposed ship sheds. It was studied with the tools of micropalaeontology, geophysics, sedimentology and geochemistry. To improve the reconstruction of the palaeoenvironmental conditions, reference samples of modern environments of the area were analysed. As indicated by marine ostracod and foraminifer taxa, the sediment core shows (from bottom to top) that the initially fully marine conditions changed to a more restricted fauna indicative for a more sheltered bay with brackish waters. This layer dates to Hellenistic times. It can, however, be shown that the siltation process had produced a lagoon system already several hundred years BC. The Elaia embayment was first used as a natural harbour. It was equipped with breakwaters in the Hellenistic period. The progressive siltation caused the abandonment of the harbour in Late Roman Times.

Ribbed moraines formed during the retreat of the Scandinavian ice sheet from eastern Himmerland, NE Jylland, Denmark

The glacial geology of Himmerland in the north-eastern part of Jylland, south of Limfjorden (Fig. 1) has never received any special attention. However, the occurrence of parallel ridges south of Torup was mentioned by Milthers (1948) who interpreted them as marginal moraines. The ridges were recently studied during mapping of eastern Himmerland. Systematic geological mapping of the area north and south of Mariager Fjord started in 2009 and was completed in 2013 (map sheet 1316 III; Pedersen et al. 2013). This was followed by the map sheet to the north (1316 IV). During the recent mapping the extent of the terrain with parallel ridges was determined (Fig. 2); the western boundary is found in Rold Skov (Pedersen & Jakobsen 2005) and the eastern boundary follows an ancient coastline in eastern Himmerland. The most impressive parallel ridges occur in a forested area east of Madum Sø where the top level of the ridge crests reaches an elevation of 95 m a.s.l. However, the majority of the crests are at 60–70 m a.s.l. and most of the ridges are c. 10–15 m high. The sediments in the ridges are dominated by coarse-grained sand and gravel, and accumulations of erratic boulders are found on the surface of the ridges.

Geomorphology of coastal formations on present and ancient sandy coasts

Anderson, A., Vilumaa, K., Tõnisson, H., Kont, A., Ratas, U., Suuroja, S., 2014. Geomorphology of coastal formations on present and ancient sandy coasts. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 090–095, ISSN 0749-0208.Many coastal sites are experiencing land uplift, so coastal formations can be found many kilometres inland from the present day shoreline. However, due to the relatively rapid, site specific and complicated development, their evolution is not very thoroughly studied yet. In this study, we analyse sediments and subsurface stratigraphy to explain the evolution and geomorphology of coastal formations (from present to ancient coastlines) located in sediment supply-limited areas. Several study sites were chosen on Tahkuna Peninsula, Hiiumaa Island in Estonia, where the rate of land uplift is 2.8 mm yr−1. Due to deficiency of sediment, dunes and old beach ridges that developed during the last 3,500 years are low (dunes up to 6–7 m, the studied ridges mostly less than 2 m). The coastal formations studied are located at different distances (up to 1 km) from the shoreline and at different altitudes (up to 13.2 m above sea level).In the current research, granulometric analysis was used for studying the coastal formations; grain size was determined by dry sieving of sediments. Additional studies were carried out with ground-penetrating radar (SIR-3000) to compare the present and former coastlines and to explain geomorphic differences. Drilling was also used and special pits were dug for the examination of mineral deposits. The preliminary results show that the sands on the present coastline are similar to those of former shorelines, which may be caused by the wind regime, time scale for coastal formation development, and underlying sediments.

Changes in coastline positions during the Holocene in the shelf of the Northwestern Black Sea

The first evidence for the reconnection of the Black Sea with the Mediterranean Sea are euryhaline mollusc species that appear in the bottom sediments. Lacustrine conditions existed over the larger part of study area at the beginning of the Holocene. Early Holocene beds are characterized by a wide distribution of continental facies (e.g. lacustrine-marshy and alluvial). The lacustrine phase was followed by a marine phase and the transition occurred around ca. 8.9–8.5 ka BP. The Holocene was marked by a gradual increase of Mytilus sp. shells in sediments. Reconstructions of coastline positions during the Holocene in the Northwestern Black Sea shelf are presented. Extensive sampling of the study area during several decades allowed the acquisition of a comprehensive data base for paleogeographic reconstructions. Positions of ancient coastlines are discussed. Analysis of relief features, lithological composition and bottom sediments distribution and faunal complexes allowed identification of paleofacies in the northwestern part of the Black Sea. Facial and paloegeographic maps of the Holocene discrete time intervals such as the Bugazian (from ca. 10.5–10 to 8.9–8.5 ka BP), the Vityazevian (from ca. 8.9–8.5 to 7.1–6.2 ka BP), the Kalamitian (from ca. 7.1–6.2 to 4.1–4.0 ka BP), and the Dzhemetinian (from ca. 4.1–4.0 to present) are presented. Dating of the sediments is based on uncalibrated radiocarbon determinations. Study of the granulometry of sediments provided evidence that supports the proposed ancient coastline positions. The samples from the cores recovered from different facial zones enabled the characterization of sedimentological environments for each time interval. The position of the early Holocene coastal sediments is marked out on the level of modern isobaths approximately from −25 to −35 m. In the range of time from ca. 8.9–8.5 to 7.1–6.2 ka BP, the coastline was located at depths from 20 to 25 m. The position of the coastline which existed from ca. 7.1–6.2 to 4.1–4 ka BP is allocated on the level of modern isobaths from −0 to −15 m. Comparison of the various positions of the coastline and their facies changes through time indicates that the Holocene transgression had a progressively and oscillatory course.

Magnetic gradient map of the mine tailings in Portman Bay (Murcia, Spain) and its contribution to the understanding of the bay infilling process

Abstract The present study is a pilot magnetic gradient survey inserted in a set of geological and geophysical works that are planned to understand the infilling process of the Portman Bay (Murcia, Spain). In a period of 33 years (from 1957 until 1990) the Portman Bay has been silted up with mine tailings. This mining waste, after being discharged into the sea, was transported by littoral currents which sorted it and concentrated the densest mineral fractions (mainly magnetite and other iron oxides). In this sedimentary context, the magnetic gradient map obtained did not detect any massive accumulation of magnetic minerals, but rather a regular distribution following parallel-banded structures in the successive contours of the bay. It has been observed that one of these magnetic bands perfectly superimposes on the ancient coastline visible in aerial photo of 1972, interpreting that this coincidence is explained by the fact that the magnetite was concentrated along the sandy ridges, oriented according to the refraction of the littoral currents. In this document we analyse the magnetic gradient map obtained in a restricted sector of the Portman Bay. This sector covers an area of 2 ha and it was chosen as a first test. The significant results suggest the suitability of this method to be conducted to the whole bay. The main objective of this study is to show the usefulness of magnetic gradient method to obtain a paleogeographic reconstruction of the infilling process of this bay.

Impacto da Mineração de Areia sobre a Química das Águas Subterrâneas, Distrito Areeiro da Piranema, Municípios de Itaguaí e Seropédica, Rio de Janeiro

Impact of sand mining upon the Groundwater Chemistry, Piranema Sand Mining District, Itaguai and Seropedica region, Rio de Janeiro. The Seropedica-Itaguai Sand Mining district supplies about 70% of sand for civil construction of Rio de Janeiro Metropolitan Region. The sand extraction process is fact by the remove of the surface sedimentary layers; make water table fi lls the produced hole. The sand extraction activities cause the oxidation of reduced sediments (ancient coast lines lithologies - mangrove environment), providing low pH values (reaching values 10 mg.L -1 ).

The impact of rapid early- to mid-Holocene palaeoenvironmental changes on Neolithic settlement at Nea Nikomideia, Thessaloniki Plain, Greece

The site of Nea Nikomideia is one of the oldest and most important Neolithic settlements in Northern Greece and the wider Balkan Peninsula, having been first occupied by early farmers at around 6500 cal. BC. Important archaeological excavations conducted in the 1960s suggested that the settlement was located close to an ancient coastline during the Neolithic. However, palaeoenvironmental change and landscape evolution in the vicinity of the site have seldom been considered in detail. Six cores from the western and central parts of the Thessaloniki Plain were therefore drilled in 2008 and subjected to palaeoenvironmental analyses, including sedimentology (LASER grain size and magnetic susceptibility measurements), chemical analysis (loss on ignition and carbonate content), stable isotopes analysis coupled with X-Ray diffraction measurements, molluscan faunal analysis and radiocarbon dating. The recognition of several important facies representing freshwater (lacustrine and fluvial) and brackish (lagoonal and marine-influenced) conditions have shed light on the environmental and landscape evolution of the western part of the Thessaloniki Plain and associated impacts on human occupation during the last 10,000 years. The general sequence proved in the cores indicates the predominance of lacustrine conditions during the early Holocene, with the occurrence of a marine transgression at c. 6000/5800 cal. B.C. This major palaeoenvironmental change corresponds with the 8.2 Ka event and is a likely cause for the desertion of Nea Nikomideia at that time. Subsequent regression of the shoreline to the east saw that the area around Nea Nikomideia returns to predominantly terrestrial conditions and the deposition of lacustrine and fluvial deposits.

Reconstructing the Roman topography and environmental features of the Sarno River Plain (Italy) before the AD 79 eruption of Somma–Vesuvius

A methodology was developed to reconstruct the Roman topography and environmental features of the Sarno River plain, Italy, before the AD 79 eruption of the Somma–Vesuvius volcanic complex. We collected, localized and digitized more than 1800 core drilling data to gain a representative network of stratigraphical information covering the entire plain. Besides other stratigraphical data including the characteristics of the pre-AD 79 stratum, the depth to the pre-AD 79 surface was identified from the available drilling documentations. Instead of a simple interpolation method, we used a machine based learning approach based on classification and regression trees to reconstruct the pre-AD 79 topography. We hypothesize that the present-day topography reflects the ancient topography and related surface processes, because volcanic deposits from the AD 79 eruption coated the ancient landscape. Thus, ancient physiographic elements of the Sarno River plain are still recognizable in the present-day topography. Therefore, a high-resolution, present-day digital elevation model (DEM) was generated. A detailed terrain analysis yielded 15 different primary and secondary topographic indices. Subsequently, a classification and regression model was applied to predict the depth of the pre-AD 79 surface combining present-day topographic indices with other physiographic data. This model was calibrated with the measured depth of the pre-AD 79 surface. The resulting pre-AD 79 DEM was compared with the classified characteristic of the pre-AD 79 stratum, identified from the drilling documentations. This allowed the reconstruction of pre-AD 79 environmental features of the Sarno River plain such as the ancient coastline, the paleo-course of the Sarno River and its floodplain. To the knowledge of the authors, it is the first time that the pre-AD 79 topography of the Sarno River plain was systematically reconstructed using a detailed database and sophisticated data mining technologies.

Archaeological remains as sea level change markers: A review

The Mediterranean Sea constitutes a unique basin from an historical and archaeological point of view, as it has been a privileged way of communication for thousands of years for the people that dwelled on its shores. Their passage has left many traces on the seabeds in the areas where the ancient commercial routes passed, and remains of structures where moorings, havens or dwellings existed. Some of these structures, nowadays submerged, offer interesting indications aiding the reconstruction of the ancient coastlines. This contribution aims to examine recent work in coastal geo-archaeology, targeting both (1) gathering and discussion of the data, particularly those pertaining to the Italian coasts; and (2) commentary on the methodological debate and verification of the possibility of a protocol that may contain unequivocal referring elements. To investigate the archaeological evidence currently underwater because of the relative sea level variations (harbour infrastructures, fishponds, villae maritimae, caves – nymphaei, private or public buildings or town quarters, pre- and protohistorical villages, quarries, caves, etc.), a clear and more coherent methodological assumption may be needed. The archaeological interpretation must initially establish the maritime and/or harbour nature and vocation of the site, determine its typology and specific usage, analyze the elements of its building techniques (that reveal themselves as meaningful markers of height or depth at the time of building) and its “functional” elements (the measure of the emerged part with respect to the average sea level), and point out the time of construction, its chronological range of usage/frequentation, the dynamics of its abandonment/destruction/obliteration. The evaluation of both the height and functional depth to the mean sea level depends on the typology of the archaeological evidence, its use and the local tide amplitudes. The surface of a pier surely has a functional elevation different from that of a haulage area or a platea or a pavement.

Ancient Coastlines in the Continental Shelf of the State of Ceará, Northeast Brazil: Evidence from Sediment Chemistry and Stable Isotopes

Continental shelf sediments from the state of Ceará, northeastern Brazil, have been studied to investigate meteoric diagenesis of marine sediments of previously defined ancient coastal lines. Major elements for 131 samples of carbonate sediments and C and O isotopes for 51 carapace samples of benthonic foraminifers of the Amphistegina radiata and Peneroplis planatus species were analyzed. Geochemical signatures of δ13C, δ18O, SiO2 (stoichiometrically calculated as quartz %), Sr and Mn, and XRD document the impact of meteoric diagenesis on relict sediments from current depths of 25-30 m, 45 m, and 80 m. Morphologies of the marine shelf at these depths, interpreted from previous bathymetric profiles, correspond to holocenic marine terraces. Despite a recent sedimentary cover, it was possible to confirm that these terraces possess relict detrital, biogenic, and continental material, that resulted from erosional reworking of ancient coastlines during the Flandrian transgression.

Ancient coastlines of Eastern Kildin

Relict Lake Mogilnoe, which is a unique object on the Murmansk coast, is located in the southeastern part of Kildin Island. Despite a history of almost a century and a half of geomorphological research of the island, the beginning of which should be related to 1860 when A. Middendorf [1] published a description of the three main terraces of Kildin Island, the genesis of the lake basin remains disputable. B.I. Koshechkin et al. presented the most detailed description of the ancient coastlines of Kildin Island [2]. He investigated five geomorphological profiles, and the main Holocene terrace levels were distinguished on the basis of the results of these investigations. All later researchers of Lake Mogilnoe cited this publication [2]. In 2007, geomorphological investigations were carried out in the eastern part of Kildin Island, which made it possible to get more exact data and supplement the results of the previous studies. During the works on geological routes, hypsometric marks of the coastal ridges and terrace levels were determined to an accuracy of 1 m. Description of loose sediments and collection of mollusk shells to determine the dates were carried out on the terraces around Lake Mogilnoe. Determination of radiocarbon age was carried out at the Laboratory of 14 C Dating of Lund University in Sweden. Radiocarbon years were transformed to calendar years on the basis of the standard calibration procedure. The value of δ 13 e was not measured but was accepted on the basis of the mean value +1‰ for marine carbonates. Neotectonic analysis was performed using standard methods [3, 4]. PECULIARITIES OF NEOTECTONIC STRUCTURE OF THE EASTERN PART OF KILDIN ISLAND The eastern part of Kildin Island is an independent neotectonic block limited from the south and north by the Karpinskii Fracture zones and from the west and east by the Fiordo-Ozernyi Fracture zones. The block of Eastern Kildin is characterized by independent neotectonic motions, which are fixed by altitude marks of the postglacier coastlines. Disjunctive structures within the block are poorly pronounced. The sublatitudinal zone dividing the block into two regions, northern and southern, is traced best of all. The northern region has a structural topography with a flat slope to the north, where it descends abruptly to the Barents Sea along the Karpinskii Fracture zone. Therefore, terrace levels within this region are developed locally. The surface of the southern region descends steeply to the south and then abruptly descends to Kildinskaya Salma as a series of cliffs divided by subhorizontal surfaces, part of which are terraces.

Principal component analysis (PCA) and mineral associations of litoraneous facies of continental shelf carbonates from northeastern Brazil

The distribution of mineral phases according to the provenance of carbonate and terrigenous facies of carbonate sediments from a large area of the continental shelf of northeast Brazil was investigated using a major element multivariate analysis approach. Heavy minerals such as ilmenite are restricted to the litoraneous facies of the continental shelf of the states of Paraíba and Pernambuco, and clay minerals are found in distal facies of the continental shelf of the State of Ceará. In the carbonate fraction, composed essentially by Mg-calcite and aragonite, there is co-variation between CaO/MgO and bathimetry in part of the studied continental shelf from depths between 15 and 20 m, apparently due to influence of the seawater temperature, degree of oxygenation and luminosity. The terrigenous facies are mainly composed of quartz, clay minerals, K-feldspars and micro-micaceous minerals, having Fe and Ti oxide and hydroxide minerals as major accessory phases. Major element behavior attests to the presence of arenaceous quartz-rich relict sediments in the 35, 60 and 80 m isobaths of the continental shelf of the state of Ceará which is here interpreted as a proxy of ancient coast lines during the Flandrian transgression.

Dấu hiệu các bờ biển cổ ở đáy biển nông ven bờ Bắc Trung Bộ vỡ tiềm năng sa khoáng liên quan

Traces of the buried Late Pleistocene ancient coastline in the coastal shallow bed of the North Central part of Vietnam and associated placer potential

Dinoflagellate diversity and distribution

Dinoflagellates are common to abundant in both marine and freshwater environments. They are particularly diverse in the marine plankton where some cause “red tides” and other harmful blooms. More than 2,000 extant species have been described, only half of which are photosynthetic. They include autotrophs, mixotrophs and grazers. They are biochemically diverse, varying in photosynthetic pigments and toxin production ability. Some are important sources of bioluminescence in the ocean. They can host intracellular symbionts or be endosymbionts themselves. Most of the photosynthetic “zooxanthellae” of invertebrate hosts are mutualistic dinoflagellate symbionts, including all those essential to reef-building corals. Roughly 5% are parasitic on aquatic organisms. The fossil record, consisting of more than 2,500 species, shows a rapid radiation of cysts, starting in the Triassic, peaking in the Cretaceous, and declining throughout the Cenozoic. Marine species with a benthic, dormant cyst stage are confined to the continental shelf and fossil cysts can be used as markers of ancient coastlines. Northern and southern hemispheres contain virtually identical communities within similar latitudes, separated by a belt of circumtropical species. A few endemics are present in tropical and polar waters. Some benthic dinoflagellates are exclusively tropical, including a distinct phycophilic community, some of which are responsible for ciguatera fish poisoning. In lakes chemical and grazing effects can be important. Predatory dinoflagellates co-occur with their prey, often diatoms.

Paleogeographic reconstructions of sea-level change and coastline migration on the northwestern Black Sea shelf over the past 18 kyr

The paper discusses the main questions of Black Sea level change during the Late Pleistocene to Holocene based on high-resolution lithological-genetic and paleogeolographic analyses of the northwest Black Sea shelf and Prichernomorean limans (estuaries). Based on the study of ancient coastlines (wave-generated coastal landforms such as beaches) with radiocarbon dating, a paleogeographic map of the northwest shelf is constructed for the period from 18 to 9.2kyrBP.Statistical data processing instrumental observations show a direct and robust relationship between sea level and river discharge at intra-annual and multi-annual periodicities. Periodicity of sea-level change at different frequencies and lengths is calculated using spectral and wavelet analysis. For the periodicity investigations, analysis included the composition and salinity of bottom sediments of two cores reconstructed from the Dnieper River discharge for the past 4000 years, and data from instrumental observations for the period of 1818–2001. The results indicate statistically significant periods of sedimentation rhythms, Dnieper discharge, and sea-level change, which are defined by their common climatic and astrophysical factors of variability. There is a relationship between the generations of coastal landforms of Dzharylgach Island and the Holocene transgressive–regressive phases of the Black Sea. The data support an oscillatory model of sea-level development for the last 18kyr. Five regressions: Drevnechernomorian, Tyraian, Khadzhibeian, Olbian (Phanagorean), and Medieval, are identified in the Holocene.

Mapeamento de recifes submersos na costa do Rio Grande do Norte, NE Brasil: Macau a Maracajau

Studies on the Brazilian continental shelf were developed between Touros and Macau-RN (NE Brazil) with the aim to mapping carbonate buildups, and especially, reef ecosystems. Remote sensing, submarine movies, bathymetric survey and diving were the methods used. This paper will focus on three main aspects of the Rio Grande do Norte reefs: 1) characterization of the coral fauna; 2) the classification and 3) the distribution of the main northriograndense carbonate buildups. Reefs environments are found predominantly on the inner shelf adjacent to Touros, at depths shallower than 10 m. These reefs generally show NW-SE orientation parallel to the coastline and constitute groupings of knolls and patch reefs. A prominent carbonate buildup, where the corals are almost absents and algae incrustation is thin, occurs in average depths of 25 m, along the northern part of Rio Grande do Norte State and is classified as sandstone bank. Others sandstone banks, with smaller lengths and heights were mapped around 10 m depth. They should be related to an ancient coastline; however the corresponding lithostratigraphic unit was not defined.This work is a contribution to the mapping of coral reef, in particular, and carbonate buildups, in general, on the Rio Grande do Norte coast.