Article

Phosphatized volcanic soils of Fernando de Noronha Island, Brazil: Paleoclimates and landscape evolution

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Abstract

Volcanic oceanic islands host soils that may hold important paleo-environmental proxies, based on vegetation and faunal evidences coupled with pedological and geomorphological indicators. In this regard, the main Brazilian oceanic island of Fernando de Noronha (FNI) still lacks a deeper and more complete analysis of its climatic history and soil evolution. We select and collect representative FNI soils to interpret their chemical, physical and mineralogical properties and to explain their changing pedogenesis and geomorphic balance, aiming at revealing the environmental and landscape evolutionary history of this island. Ten soil pedons on phonolites, ankaratrites and the associated pyroclastic rocks were collected in June/2018. Six profiles were classified as Inceptisols, one as Entisol, one as Mollisol, one as Vertisol and another as the first Oxisol ever described in a Brazilian oceanic island. The pH ranged between 5.0 and 6.0 in the more developed, dystrophic and Al-saturated soils, whereas alkaline pHs were found in the eutrophic and Na-rich pedons. For the latter group, chemical and physical attributes are closely associated with the parent material composition, whereas in the former, present day soil features overprint paleoweathered regoliths and former pedogenetic processes. High concentrations of available phosphorus (P) were observed in all soils and horizons, even at depths greater than 150 cm, and P forms were detected as amorphous or poorly-crystalline phosphates (Al, Fe, Na, Ca and K). High- and low-activity clay minerals coexist, combined with gibbsite and unstable primary minerals, indicating the polygenetic nature of FNI soils. A combined pedogeomorphological analysis indicated the existence of a high paleoweathered plateau with relict soils, and erosional surfaces hosting younger soils. Results showed the succession of at least three distinct main paleoclimates since the Pliocene and a post-magmatic model for landscape evolution. The unreported, widespread and intense phosphatization of all soils and paleosurfaces is attributed to a past large population of birds nesting all over the island, corroborating old historical records of the island’s early occupation. Report the occurrence of Brazil’s first ornithogenic Oxisol with more than 500 mg/kg of bioavailable P.

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... The soils identified in Fernando de Noronha -Ferralsols, Cambisols, Vertisols, Leptosols and Regosols -are strongly influenced by geologic and geomorphologic attributes (Silveira et al., 2020), with greatest developed soils in preserved plateaus of the highlands, and shallower soils in lowlands and colluvial volcanic slopes (Marques, 2004). The climate is affected by the Inter-Tropical Convergence Zone (ITCZ), with heavy, concentrated rains and strong winds (Angulo et al., 2013). ...
... Normally, these conditions are observed in environments characterized by strongly seasonal precipitations such as xeric climates. These conditions were observed in Fernando de Noronha Island, and according to Silveira et al. (2020), the presence of 2:1 clay minerals is a consequence of pedogenesis due to the present-day climate, as renewed erosion of weathered mantles upslope, expose new rock fronts to further cycles of pedogenesis, influenced by the low precipitation and high evapotranspiration rates. The Cambisol (PN4) is a typical soil formed under this condition, and part of the sediments deposited in the fluvial environment of PN3 may be associated with erosion of upland soils similar to PN4. ...
... For example, the high P-content in some superficial horizons is associated with ornithogenic activity by marine birds. This process is recognized as phosphatization and occurs in both studied islands, such as reported by Oliveira (2008) and Silveira et al. (2020) at Fernando de Noronha, and by Clemente et al. (2009), Firme Sá (2010, Machado (2016) and Machado et al. (2017) at Trindade. Bone fragments observed in photomicrographs, and identification of apatite by XRD analysis confirm the ornithogenesis and phosphatization process. ...
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... The type of soil could also influence the enrichment from avian material because guano deposited on the rocks loses more of its nitrogen by volatilization than when deposited on sediments or vegetation (Lindeboom 1984;Blackall et al. 2008). In addition, the presence of historical depositions, such as ornithogenic soils (Oliveira et al. 2014;Silveira et al. 2020), could make nitrogen and phosphorous available to the terrestrial food web even during seasons and years with no or limited breeding activity. Finally, areas free of nutrient-carrying animals (e.g. ...
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... Most of the soils are young and shallow, and were influenced by the generalized phosphatization of birds that led to the formation of a Latosol. This unusual soil is sandy, and is composed of bioclastic and carbonate material in dunes and emerged marine platforms (Schaefer et al. 2017, Silveira et al. 2020. ...
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Environmental interpretation seeks to reveal meanings to provoke personal connections between the public and the protected heritage. In the specific case of geological heritage, it determines and communicates the meaning of a geological and geomorphological phenomenon, event or location. There is a range of nature tourism activities that can promote interpretation of this heritage. The practice of properly organized scuba diving can bring benefits both to conservation of the environment and to local communities. Fernando de Noronha is one of the best dive sites in Brazil and actions focused on as-pects of marine geology add even more value to the activity. In this sense, we sought to investigate the opinion of divers about environmental interpretation and aspects of marine geology in the archipelago by applying a questionnaire. The questionnaire was applied online between April 2018 and May 2019, with 100 individuals who had practiced scuba diving in the archipelago at least once. Different data collection techniques were applied (convenience, purposive sampling, quota and snowball). The main results indicate that information on marine geology is relevant for the scuba diving activity, and this type of action can contribute to a more conscious attitude towards island sustainability.
... In Antarctica, it also occurs in areas affected by many other birds, such as giant petrels, skuas, kelps gulls (Abakumov et al., 2020), and marine mammals, such as fur seals and elephant seals (Bedernichek et al., 2020). Elsewhere, phosphatization and ornithogenic soils have been also recorded in many islands of the South Atlantic by Oliveira et al. (2014) and Silveira et al. (2020) at Fernando de Noronha archipelago, and Machado et al. (2017) at Trindade Island. Otero et al. (2015) showed high P contents in the Atlantic Islands of Galicia National Park (NW Iberian Peninsula), under seagull nests. ...
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Chapter
Several examples of phosphorite weathering (Morocco, Senegal, Israel), are studied. Weathering of phosphorites is shown to begin by loss of CO2 from the carbonate-fluor-apatite, which tends toward a fluor-apatite; dolomite loses its Mg, then calcite is leached. When calcium carbonates are eliminated, calcium apatite transforms to aluminum- or iron-phosphates. Four cases are studied, two of slight weathering by J. L. and L. P., one of intense weathering in an aluminous environment by R. F. and one of intense weathering in an environment rich in iron by Y. N. and Y. S.; the discussion is by all authors.
Chapter
The known natural phosphate minerals exceed 250 in number (Fisher 1973). However, the more common ones are small in number and belong to the apatite family. This family constitutes the main group of primary phosphates of the lithosphere. The majority of the other minerals result from a supergene alteration by groundwaters, or bat- and bird-guanos. This alteration has been well described in detail by Altschuler (1973), in a fundamental synthesis based on three main topics: the weathering of marine phosphorites, the weathering of carbonatites and the weathering caused by acid guanos. The weathering of phosphatic igneous and metamorphic rocks is not mentioned, probably because it is little known, except in the northeast of Brazil (Lima Da Costa, verbal comm.). Since Altschuler’s synthesis, many studies have been published, some related to the weathering of phosphorites, others to the genesis of new minerals during the weathering process. Most of the mineralogical results obtained from these works are shown in Table 1. Consideration of Table 1 permits the findings of Altschuler (1973, p 78–80) to be extended and allows some general conclusions on the conditions of phosphate minerals weathering and on their behavior during weathering.
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A substantial strengthening of the South American monsoon system (SAMS) during Heinrich Stadials (HS) points toward decreased cross-equatorial heat transport as the main driver of monsoonal hydroclimate variability at millennial time scales. In order to better constrain the exact timing and internal structure of HS1 over tropical South America, we assessed two precisely dated speleothem records from central-eastern and northeastern Brazil in combination with two marine records of terrestrial organic and inorganic matter input into the western equatorial Atlantic. During HS1, we recognize at least two events of widespread intensification of the SAMS across the entire region influenced by the South Atlantic Convergence Zone (SACZ) at 16.11–14.69 kyr B.P. and 18.1–16.66 kyr B.P. (labeled as HS1a and HS1c, respectively), separated by a dry excursion from 16.66 to 16.11 kyr B.P. (HS1b). In view of the spatial structure of precipitation anomalies, the widespread increase of monsoon precipitation over the SACZ domain was termed “Mega-SACZ.”
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Entire structures of freshwater sponges are rare in the paleontological record and no register existed for the Pleistocene. A previous study of the spicules of such sponges composing pleistocenic strata of the Cemiterio Paleolake, Brazil, led to the discovery of several in situ preserved gemmules. The present research aimed to identify the sponge species which produced these gemmules, their relationship to the already described spicules found in the lake strata and enter a taphonomic enquiry towards the factors which would have led to this remarkable preservation. The materials were mounted for analysis at SEM. The gemmules pertain to the extant species Corvoheteromeyenia australis, Dosilia pydanieli, Radiospongilla amazonensis and Corvomeyenia thumi. Young gemmules of Heterorotula fistula, a sponge known only from loose spicules in spongillite deposits were also detected and are for the first time figured, confirming the species status. Two factors would have favored this exceptional gemmular preservation. The abundance ofyoung gemmules indicates short immersion periods, which led to the incipient development of pneumatic coats, impairing their buoyancy and accelerating deposition in the lake bottom. Algal blooms, formed next with probable heat and desiccation, would have provided an elastic but consistent crust over the recently deposited gemmules, preventing their dismantling. Radiocarbon dating of the basal-most layer indicated an age of more than 53,780 C-14 years BP.
Article
The percentage of woody dicots with entire-margined leaves in a flora is known to be positively correlated with mean annual temperature (Leaf Margin Analysis — LMA) but this relationship is not globally uniform. In particular the floras of Australia and New Zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the Northern Hemisphere. This difference is more marked in New Zealand where the LMA relationship appears entirely absent. Here we amass data for both Northern and Southern hemispheres using standard protocols and show that regional variations in the leaf margin–mean annual temperature relationship are real but become less significant when other characters are included. Even New Zealand falls into line and most of the mean annual temperature signal in New Zealand floras is encoded in non-margin features. We introduce a new CLAMP (Climate Leaf Analysis Multivariate Program) calibration dataset for the Southern Hemisphere, comprising leaf physiognomic data from Argentina, Bolivia, South Africa, Australia, New Zealand and other Pacific Islands that offers comparable precision for climate prediction to similar datasets derived from the Northern Hemisphere.
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Fossil floras are an important source of quantitative terrestrial paleoclimate data. Many paleoclimate estimates are based on relationships observed in modern vegetation between leaf morphology and climate, such as the increase in the percentage of entire-margined species with increasing temperature and the increase in leaf size with increasing precipitation. An important question is whether these observed relationships are universal or regional; for example, recent stud- ies suggest that significant differences exist between floras from three domains: the Northern Hemi- sphere, New Zealand/Australia, and subalpine zones. Also, debate exists over which statistical models of modern data sets, univariate or multivariate, provide the most accurate estimates of pa- leoclimate. In this study, 12 foliage samples from living Bolivian forests are compared with data sets from different regions. Models based on data sets from North America and Japan, namely the Climate-Leaf Analysis Multivariate Program (CLAMP) data set of J. A. Wolfe, and from east Asia produce reasonably accurate estimates of temperature and precipitation, suggesting that the cli- mate-leaf morphology relationships for Bolivian vegetation do not differ significantly from those for Northern Hemisphere vegetation. The mean leaf size for a given mean annual precipitation is smaller than for a data set from the Western Hemisphere and Africa, but this difference is most likely due to different sampling methods. As for estimating climate from fossil floras, these results, along with the analysis of four other regional data sets, imply that the most accurate climate es- timates will be produced by the predictor data set with the most similar climate-leaf morphology relationships. Unfortunately, our present lack of understanding of why climate-morphology rela- tionships vary between the North America/Japan, New Zealand/Australia, and subalpine domains makes it difficult to identify data sets similar to paleofloras. Until we learn more, it is probably best to compare fossil floras to predictor data sets from the same domain. The performance of the var- ious statistical methods depends on the nature of the predictor data set. Multiple regression anal- ysis tends to produce the most accurate estimates for small data sets with a narrow range of en- vironmental variation that have similar relationships to the flora, and linear regression or canonical correspondence analysis for the larger and more varied CLAMP data set. If a similar predictor data set is not available, then nearest-neighbor analysis can still produce accurate paleoclimate esti- mates.
Article
Millennial climate oscillations of the glacial interval are interrupted by extreme events, the so-called Heinrich events of the North Atlantic. Their near-global footprint is a testament to coherent interactions among Earth's atmosphere, oceans, and cryosphere on millennial timescales. Heinrich detritus appears to have been derived from the region around Hudson Strait. It was deposited over approximately 500 ± 250 years. Several mechanisms have been proposed for the origin of the layers: binge-purge cycle of the Laurentide ice sheet, jökulhlaup activity from a Hudson Bay lake, and an ice shelf buildup/collapse fed by Hudson Strait. To determine the origin of the Heinrich events, I recommend (1) further studies of the timing and duration of the events, (2) further sedimentology study near the Hudson Strait, and (3) greater spatial and temporal resolution studies of the layers as well as their precursory intervals. Studies of previous glacial intervals may also provide important constraints.
Chapter
Five long-term oxygen isotope (δ) records along ice cores are discussed, in particular two from the Greenland ice sheet that exhibit persistent δ oscillations with a quasi-periodicity of ca. 2550 years. A detailed study of the δ cycles in the Wisconsin glaciation show that they cannot be ascribed to discontinuities in the cores, nor to ice-dynamic instabilities in the ice sheet. In the Holocene, the δ cycles are less pronounced, but they are concurrent with the fluctuating glacier extention elsewhere, which substantiates their climatic significance. An anti-correlation with 14C concentration in atmospheric CO2, and with 10Be deposition rates on the ice sheets, suggests a connection between climate and solar processes, but a conclusion on this point must await clarification of the terrestrial circulation and mixing processes, and the relationship between the solar outputs of radiation and particulate matter.
Article
Aim Our aims were: (1) to characterize the linear relationship between the proportion of woody dicotyledonous species with entire-margined leaves (E) and mean annual temperature (MAT) from a southern temperate flora that still harbours many lineages that originated under warmer climates; (2) to compare this relationship with those developed from floras of different regions of the world; and (3) to contrast temperature predictions based on leaf margins of the native southern flora versus the naturalized alien flora, mostly of boreal origin. Location The temperate forest of southern South America (TFSA). Methods At each 1° latitudinal band, we estimated E based on species latitudinal ranges and MAT from both an isotherm map and a global temperature grid. We also calculated E from five local floras located between 40 and 43° S, and from the naturalized alien flora of Nahuel Huapi National Park in southern Argentina. Results We found a close relationship between E and MAT for the TFSA. Equations developed from floras of the Northern Hemisphere overestimated extant temperatures of this biome by 6–10 °C at both geographical and local spatial scales. On the other hand, MAT predictions from leaf margins of the alien flora were similar to the actual MAT. A published regression between E and MAT from tropical South America was remarkably similar to the one we estimated from the TFSA. This tropical equation predicted accurately the temperatures observed for this temperate biome based on leaf margins of the native flora. Main conclusions Despite massive plant extinction due to environmental cooling and biogeographical isolation during the Tertiary, leaf-margin analysis reveals that the flora of the TFSA still reflects its original development under the warmer conditions of western Gondwana and its past connections with low-latitude forest floras of tropical South America.
Article
Aim The relationship between the proportion of species with an entire leaf margin (pE) and mean annual temperature (MAT) is one of the most powerful tools for estimating palaeotemperatures. However, phylogenetic and phytogeographic constraints on this relationship have remained unexplored. Here we investigate the pE–MAT relationship for modern floristic assemblages from southern South American forests, assess its conformity to other models and test for the existence of historical constraints on pE–MAT models.
Article
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Article
Several methods of estimating thermodynamic data of natural phosphates were unable to predict with enough accuracy stability fields of such minerals and the parageneses observed in natural conditions. Detailed observations made on lateritic weathering profiles, from the bottom to the top, yield the following mineral associations: Fluor-carbonate-apatite + montmorillonite + calcite →. fluor-carbonate-apatite + montmorillonite →. fluor-carbonate- apatite + kaolinite →. crandallite + kaolinite → wavellite + kaolinite → augelite → gibbsite. A refined method for estimating Gibbs free energies of formation of these phosphates is proposed. A first step of estimation is based on the summation of the Gibbs free energies of formation of simple components and an additional term which depends on the nature of cations in each compound. A second calibration step is based on the correction of the additional term so that the Gibbs free energies of formation and the fields of stability of the phosphates and clay minerals would be in good agreement with the natural observed sequence. These estimations yield the following values.
Article
Eocene vegetation and climate data from tropical latitudes are sparse despite special interest in the Eocene as the warmest epoch of the Cenozoic and an often-cited analogue for greenhouse Earth conditions. Tropical Africa is noteworthy for its shortage of Eocene fossils, which could serve as proxies for climate and reveal community structural evolution during the continent's geographic isolation. In this paper, we report paleobotanical remains from a middle Eocene crater lake at 12°S paleolatitude in north central Tanzania, which provide a plant community reconstruction indicating wooded, rather than forest, vegetation and precipitation estimates near modern (660 mm/year). The plant community was dominated by caesalpinioid legumes and was physiognomically comparable to modern miombo woodland. Paleoprecipitation estimates, the first for the Paleogene of Africa, are calculated from fossil leaf morphology using regression equations derived from modern low-latitude leaves and climate. Mean annual precipitation estimates are 643±32 and 776±39 mm/year, and wet months precipitation estimates (all months averaging≥50 mm) are 630±38 and 661±38 mm. A slightly larger proportion of annual precipitation occurred in the dry months compared with today, which may indicate greater equability of precipitation in the Eocene.
Article
Are models that predict mean annual temperature (MAT) from leaf morphology applicable globally? Fifteen models that predict MAT from leaf morphology were tested on thirty floral samples from tropical South America to determine the degree to which models based on published data that are primarily from other regions are applicable to floras from tropical South America. The models included are based on regional data from North America, South America, and Asia. Of the fifteen models tested, five are simple linear regressions, six are multiple linear regressions, two are canonical correspondence analyses, and two are correspondence analyses followed by nearest neighbor analyses. For the seven modern floras with MAT ≤21°C, every model overestimates MAT. For the 23 modern floras with MAT >21°C, all models produce variable results without a systematic error. The range of average model errors is 2.7–7.3°C, while the absolute extremes of error are 0 and 15.1°C. Average 95% predictive confidence intervals range from 1.6 to 6.9°C. Predicted MAT falls within the published standard error of the model for 0–67% of the South American test floras. Evaluating the seven sites with MAT ≤21°C separately from the 23 sites with MAT >21°C shows that no equation accurately estimates MAT of the majority of low-temperature sites, but that four equations accurately estimate >50% of high-temperature sites. The results suggest that at least for sites of unknown or high elevation, mean annual temperature of fossil floras from tropical South America may be better predicted from models based on the leaf morphology of tropical South American floras.
Article
Regression models are defined for leaf physiognomic and climate variables from 30 modern equatorial African plant communities. Herbarium specimens provide physiognomic data for published species lists for the 30 sites; climate data are from a variety of published sources. By limiting the sampled region to equatorial Africa, where annual amount and seasonality of rainfall are critical determinants of vegetation, leaf physiognomy is found to be related linearly to moisture variables. Principal components analysis demonstrates that the pattern of variation among leaf variables is primarily a function of mean annual and wet months (total of all months with ≥50 mm) rainfall. Multiple regression models are derived for mean annual rainfall, wet months rainfall and the number of dry months. Accuracy of each model is tested by comparing the adjusted predicted values (the value for a case when it is not included in calculation of the regression line) to the actual climate values at the 30 sites. Leaf size is the strongest correlate of moisture; the mesophyll size class has the most significant positive relationship with annual and wet months rainfall. Entire-margined species increase with wet months rainfall and temperature. Acuminate tip and length/width ratio are also positively related to mean annual and wet months rainfall. Rounded base, emarginate tip, and acute tip are inversely related to rainfall variables. Regression models derived from modern plants and climate can be used to reconstruct seasonal and annual rainfall from Cenozoic African leaf fossils.
Article
The “Baja BC hypothesis”, which postulates that western Washington State, British Columbia and southern Alaska originated at the latitude of Mexico, has pitted paleomagnetic results against long-held interpretations about the tectonic evolution of western North America. In this paper we develop a new paleobotanical method for estimating paleolatitude and apply it to this problem. We start by showing that the modern MAT field for North America is well correlated with latitude, demonstrating the feasibility of using MAT to estimate paleolatitude. A compilation of MAT and floral data from 84 modern sites in Central and North America is used to establish a new prediction relationship, MAT = 1.32 + 28.99P, where P is the proportion of smooth-margined species within a floral sample at a site. Our analysis also includes a more complete estimate of the uncertainties associated with estimating MAT from a measurement of P. Using modern data, we show that MAT and P can be used to estimate latitude as well. We then apply this approach to resolve the paleolatitude of Baja BC. Eleven floral sites from stable North America are used to establish the latitudinal MAT profile for North America during the Albian and Cenomanian. A floral site from the Winthrop Formation, a mid-Cretaceous (110–100 Ma) fluvial unit in the Methow basin of northern Washington State, is linked to the Baja BC block and predates its proposed northward offset. Forty-three morphospecies of dicotyledonous angiosperm leaves from the Winthrop Formation give P = 0.76, which is equivalent to a MAT of 23.4 °C, indicating a subtropical to tropical climate. We use the North American MAT profile to estimate a paleolatitude of 38.4°N for the Winthrop flora, indicating ∼ 2200 km of northward offset relative to stable North America.