Sedimentology and planktonic foraminiferal dissolution during the latest Cretaceous in the South Atlantic

A high-resolution (10-20 kyr) record of variations in CaCO3 content and dissolution was established for latest Cretaceous (last 0.7 Myr) deep-sea sediments from the South Atlantic Ocean (DSDP Site 516 from the Rio Grande Rise, and sites 525 and 527 from the Walvis Ridge). The degree of fragmentation of planktonic foraminifera (DFP) was used as a measure of calcite dissolution. High negative correlations between DFP and other independent measures of carbonate dissolution (percentage of sand fraction, absolute abundance of planktonic foraminifera, and planktonic/benthic foraminiferal ratio) validate its use as a sensitive index of calcite dissolution in upper Maastrichtian deep-sea sediments. Very high DFP and a significant negative correlation between DFP and CaCO 3 content suggest that Site 516 was located below the foraminiferal lysocline during the entire interval studied. Such a shallow position of the lysocline (paleodepth of Site 516 was 1.2 km) may be explained by "upwelling" of corrosive deep waters along the southern margin of the Rio Grande Rise. Sites 525 and 527 were located above the foraminiferal lysocline; however, three short periods of enhanced dissolution were recognised at Site 525 (paleodepth 1 km) and one interval of strong dissolution was identified at Site 527 (paleodepth 2.7 km). The lack of correspondence between the dissolution regimes at sites from the Walvis Ridge suggests limited deep-water communication across this physiographic barrier. Two of the dissolution maxima recognised at Site 525 correspond to carbonate maxima at Site 527. Variations in "upwelling" intensity along the Walvis Ridge, resulting in fluctuations in primary productivity in this area, may be the proximal cause of both carbonate cycles at Site 527 and dissolution cycles at Site 525. We suggest that development of the bottom Ekman layer between a hypothetical westward geostrophic current and the topographical height of the Rio Grande Rise-Walvis Ridge system may be a plausible hydrodynamical explanation for the proposed "'upwelling" along the southern margin of this topographical structure.

Organic matter deposition along the Kara and Laptev Seas continental margin (eastern Arctic Ocean) during last deglaciation and Holocene

Organic petrologic (maceral analysis) and bulk organic-geochemical studies were performed on five sediment cores from the Eurasian continental margin to reconstruct the environmental changes during the last not, vert, similar13 000 yr. The core stratigraphy is based on AMS-14C dating, and correlation by magnetic susceptibility and lithostratigraphic characteristics. Variations in terrigenous, freshwater, and marine organic matter deposition document paleoceanographic and paleoclimatic changes during the transition from the last deglaciation to the Holocene. Glacigenic diamictons deposited in the St. Anna Trough (northern Kara Sea) during the Last Glacial Maximum (LGM) are characterized by reworked terrigenous organic matter. In contrast, the Laptev Sea shelf was not covered by an ice-sheet, but was exposed by the lowered sea level. Increased deposition of marine organic matter (MOM) during deglaciation indicates enhanced surface-water productivity, possibly related to influence of Atlantic waters. The occurrence of freshwater alginite gives evidence for river discharge to the Kara and Laptev Seas after the LGM. At the eastern Laptev Sea slope, the first influence of Atlantic water masses is indicated by an increase in the contents of MOM and dinoflagellate cysts, with Operculodinium centrocarpum prior to not, vert, similar10 000 yr BP. High sedimentation rates in the Kara and the Laptev Seas with the adjacent slope at the beginning of the Holocene are presumably related to increased freshwater and sediment discharge from the Siberian rivers. Evidence for elevated Holocene freshwater discharge to the Laptev Sea has been found between not, vert, similar9.8 and 9 kyr BP, at not, vert, similar5 kyr BP and at not, vert, similar2.5 kyr BP. In the Kara Sea, an increased freshwater signal is obvious at not, vert, similar8.5 kyr BP and at not, vert, similar5 kyr BP. Higher portions of MOM were accumulated in the St. Anna Trough and at the Eurasian continental margin at several intervals during the Holocene. Increased primary productivity during these intervals is explained by seasonally ice-free conditions possibly associated with increased inflow of Atlantic waters.

Comparison of glacial/interglacial carbonate concentrations in Atlantic sediments

To assess the regional effects of glaciation on sedimentation in the Atlantic Ocean we compare sediment types, distributions, and rates between Recent (core top) and last glacial maximum (LGM: ~18,000 years B.P.) stratigraphic levels. Based upon smear slides and carbonate analyses in 178 cores we find that glacial age carbonate content is generally lower than Recent. During both the Recent and LGM, carbonate content shows an east/west asymmetry with western basins exhibiting lower carbonate values. Input of ice-rafted detritus into the North Atlantic during LGM time interrupts this topographic control on carbonate distribution considerably farther south than at present; in the South Atlantic this effect is minor. Comparison of LGM and Recent sediment distributions indicates that the LGM seafloor was dominated by biogenic oozes, calcareous clays, and clays, while the Recent is dominated by biogenic oozes and marls. Coarse-grained detritus is much more prevalent in LGM sediments, derived not only from glacial input but also from fluvial and aeolian sources. Sedimentation rates, calculated from LGM to Recent sediment thickness in cores, are <4 cm/1000 yr for most of the ocean. Higher rates are typical of the continental margin off the Amazon River, the North American Basin, and a small region off west equatorial Africa.

K-Ar and 40Ar/39Ar ages of dikes emplaced in the onshore basement of the Santos Basin, Resende area, SE Brazil: implications for the South Atlantic opening and tertiary reactivation

New K-Ar and Ar-40/Ar-39 data of tholeiitic and alkaline dike swarms from the onshore basement of the Santos Basin (SE Brazil) reveal Mesozoic and Tertiary magmatic pulses. The tholeiitic rocks (basalt, dolerite, and microgabbro) display high TiO2 contents (average 3.65 wt%) and comprise two magmatic groups. The NW-oriented samples of Group A have (La/Yb)N ratios between 15 and 32.3 and range in age from 192.9 +/- 2.2 to 160.9 +/- 1.9 Ma. The NNW-NNE Group B samples, with (La/Yb)(N) ratios between 7 and 16, range from 148.3 +/- 3 to 133.9 +/- 0.5 Ma. The alkaline rocks (syenite, trachyte, phonolite, alkaline basalts, and lamprophyre) display intermediate-K contents and comprise dikes, plugs, and stocks. Ages of approximately 82 Ma were obtained for the lamprophyre dikes, 70 Ma for the syenite plutons, and 64-59 Ma for felsic dikes. Because Jurassic-Early Cretaceous basic dikes have not been reported in SE Brazil, we might speculate that, during the emplacement of Group A dikes, extensional stresses were active in the region before the opening of the south Atlantic Ocean and coeval with the Karoo magmatism described in South Africa. Group B dikes yield ages compatible with those obtained for Serra Geral and Ponta Grossa magmatism in the Parana Basin and are directly related to the breakup of western Gondwana. Alkaline magmatism is associated with several tectonic episodes that postdate the opening of the Atlantic Ocean and related to the upwelling of the Trindade plume and the generation of Tertiary basins southeast of Brazil. In the studied region, alkaline magmatism can be subdivided in two episodes: the first one represented by lamprophyre dykes of approximately 82 Ma and the second comprised of felsic alkaline stocks of approximately 70 Ma and associated dikes ranging from 64 to 59 Ma. (c) 2005 Elsevier Ltd. All rights reserved.

Building Regional Security: Cooperation in the 21st Century: The Case of the Caribbean Regional Security System [RSS]

Small states that lack capacity and act on their own may fall victim to international and domestic terrorism, transnational organized crime or criminal gangs. The critical issue is not whether small Caribbean states should cooperate in meeting security challenges, but it is rather in what manner, and by which mechanisms can they overcome obstacles in the way of cooperation. The remit of the Regional Security System (RSS) has expanded dramatically, but its capabilities have improved very slowly. The member governments of the RSS are reluctant to develop military capacity beyond current levels since they see economic and social development and disaster relief as priorities, requiring little investment in military hardware. The RSS depends on international donors such as the USA, Canada, Great Britain, and increasingly China to fund training programs, maintain equipment and acquire material. In the view of most analysts, an expanded regional arrangement based on an RSS nucleus is not likely in the foreseeable future. Regional political consensus remains elusive and the predominance of national interests over regional considerations continues to serve as an obstacle to any CARICOM wide regional defense mechanism. Countries in the Caribbean, including the members of the RSS, have to become more responsible for their own security from their own resources. While larger CARICOM economies can do this, it would be difficult for most OECS members of the RSS to do the same. The CARICOM region including the RSS member countries, have undertaken direct regional initiatives in security collaboration. Implementation of the recommendations of the Regional Task Force on Crime and Security (RTFCS) and the structure and mechanisms created for the staging of the Cricket World Cup (CWC 2007) resulted in unprecedented levels of cooperation and permanent legacy institutions for the regional security toolbox. The most important tier of security relationships for the region is the United States and particularly USSOUTHCOM. The Caribbean Basin Security Initiative [CBSI] in which the countries of the RSS participate is a useful U.S. sponsored tool to strengthen the capabilities of the Caribbean countries and promote regional ownership of security initiatives. Future developments under discussion by policy makers in the Caribbean security environment include the granting of law enforcement authority to the military, the formation of a single OECS Police Force, and the creation of a single judicial and law enforcement space. The RSS must continue to work with its CARICOM partners, as well as with the traditional “Atlantic Powers” particularly Canada, the United States and the United Kingdom to implement a general framework for regional security collaboration. Regional security cooperation should embrace wider traditional and non-traditional elements of security appropriate to the 21st century. Security cooperation must utilize to the maximum the best available institutions, mechanisms, techniques and procedures already available in the region. The objective should not be the creation of new agencies but rather the generation of new resources to take effective operations to higher cumulative levels. Security and non-security tools should be combined for both strategic and operational purposes. Regional, hemispheric, and global implications of tactical and operational actions must be understood and appreciated by the forces of the RSS member states. The structure and mechanisms, created for the staging of Cricket World Cup 2007 should remain as legacy institutions and a toolbox for improving regional security cooperation in the Caribbean. RSS collaboration should build on the process of operational level synergies with traditional military partners. In this context, the United States must be a true partner with shared interests, and with the ability to work unobtrusively in a nationalistic environment. Withdrawal of U.S. support for the RSS is not an option.

Pirates, exiles, and empire: English seamen, Atlantic expansion, and Jamaican settlement, 1558–1658

A life of piracy offered marginal men a profession with a degree of autonomy, despite the brand of "outlaw" and the fear of prosecution. At various times throughout history, governments and crowned heads suspended much of their piracy prosecution, licensing men to work as "privateers" for the state, supplementing naval forces. This practice has a long history, but in sixteenth-century England, Elizabeth I (1558-1603) significantly altered this tradition. Recognizing her own weakness in effectively prosecuting these men and the profit they could contribute to the government, Elizabeth began incorporating pirates into the English naval corps in peacetime—not just in war. This practice increased English naval resources, income, and presence in the emerging Atlantic World, but also increased conflict with the powerful Spanish empire. By 1605, making peace with Spain, James VI/I (1603-1625) retracted Elizabeth's privateering promotion, prompting an emigration of English seamen to the American outposts they had developed in the previous century. Now exiles, no longer beholden to the Crown, seamen reverted back to piracy. The Carolinas and Jamaica served as bases for these rover communities. In 1650, the revolutionary leader Oliver Cromwell (1649-1658) once again recognized the merits of such policies. Determined to demonstrate his authority and solidify his rule, Cromwell offered citizenship and state support to Caribbean exiles in exchange for their aiding of his navy in the taking of Spanish Jamaica. Official chartering of Port Royal, Jamaica served as reward for these men's efforts and as the culmination of a century-long cycle of piracy legislation, creating one of England's most lucrative colonies in the middle of a traditionally Spanish Caribbean empire. Through legal and diplomatic records, correspondence, and naval and demographic records from England and Spain, this dissertation explores early modern piracy/privateering policy and its impact on the development of the Atlantic World. European disputes and imperial competition converged in these piracy debates with significant consequences for the definitions of criminality and citizenship and for the development of Atlantic empire.

Atlantic Ais in the Sixteenth and Seventeenth Centuries: Maritime Adaptation, Indigenous Wrecking, and Buccaneer Raids on Florida’s Central East Coast

The Ais were a Native American group who lived along the Atlantic shoreline of Florida south of Cape Canaveral. This coastal population’s position adjacent to a major shipping route afforded them numerous encounters with the Atlantic world that linked Europe, Africa, the Caribbean, and the Americas. Through their exploitation of the goods and peoples from the European shipwrecks thrown ashore, coupled with their careful manipulation of other Atlantic contacts, the Ais polity established an influential domain in central east Florida during the sixteenth and seventeenth centuries. The pre-contact peoples of Florida’s east coast, including the ancestors of the Ais, practiced a maritime adaptation concentrated on the exploitation of their bountiful riverine, estuarine, and marine environments. The Ais then modified their maritime skills to cope with the opportunities and challenges that accompanied European contact. Using their existing aquatic abilities, they ably salvaged goods and castaways from the Spanish, French, English, and Dutch vessels dashed on the rocks and reefs of Florida’s coast. The Ais’ strategic redistribution of these materials and peoples to other Florida Native Americans, the Spaniards of St. Augustine, and other passing Europeans gained them greater influence. This process, which I call indigenous wrecking, enabled the Ais to expand their domain on the peninsula. Coastal Florida Native Americans’ maritime abilities also attracted the attention of Europeans. In the late seventeenth century, English buccaneers and salvagers raided Florida’s east coast to capture indigenous divers, whom they sent to work the wreck of a sunken Spanish treasure ship located in the Bahamas. The English subsequently sold the surviving Native American captives to other Caribbean slave markets. Despite population losses to such raids, the Ais and other peoples of the east coast thrived on Atlantic exchange and used their existing maritime adaptation to resist colonial intrusions until the start of the eighteenth century. This dissertation thus offers a narrative about Native Americans and the Atlantic that is unlike most Southeastern Indian stories. The Ais used their maritime adaptation and the process of indigenous wrecking to engage and exploit the arriving Atlantic world. In the contact era, the Ais truly became Atlantic Ais.

Compilation of downward flux observations from sediment trap deployments in the Atlantic Ocean - Contribution to EURO-BASIN's Data integration

We provide a compilation of downward fluxes (total mass, POC, PON, BSiO2, CaCO3, PIC and lithogenic/terrigenous fluxes) from over 6000 sediment trap measurements distributed in the Atlantic Ocean, from 30 degree North to 49 degree South, and covering the period 1982-2011. Data from the Mediterranean Sea are also included. Data were compiled from different sources: data repositories (BCO-DMO, PANGAEA), time series sites (BATS, CARIACO), published scientific papers and/or personal communications from PI's. All sources are specifed in the data set. Data from the World Ocean Atlas 2009 were extracted to provide each flux observation with contextual environmental data, such as temperature, salinity, oxygen (concentration, AOU and percentage saturation), nitrate, phosphate and silicate.

(Table S1) Stable carbon and oxygen isotope ratios of benthic foraminifera of the western Atlantic Ocean

Oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa Cibicidoides and Planulina from 25 new piston cores, gravity cores, and multicores from the Brazil margin. The cores span water depths from about 400 to 3000 m and intersect the major water masses in this region. These new data fill a critical gap in the South Atlantic Ocean and provide the motivation for updating the classic glacial western Atlantic d13C transect of Duplessy et al. (1988). The distribution of 13C of SumCO2 requires the presence of three distinct water masses in the glacial Atlantic Ocean: a shallow (~1000 m), southern source water mass with an end-member d13C value of about 0.3-0.5 per mil VPDB, a middepth (~1500 m), northern source water mass with an end-member value of about 1.5 per mil, and a deep (>2000 m), southern source water with an end-member value of less than -0.2 per mil, and perhaps as low as the -0.9 per mil values observed in the South Atlantic sector of the Southern Ocean (Ninnemann and Charles, 2002, doi:10.1016/S0012-821X(02)00708-2). The origins of the water masses are supported by the meridional gradients in benthic foraminiferal d18O. A revised glacial section of deep water d13C documents the positions and gradients among these end-member intermediate and deep water masses. The large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation.

Nd, Pb and Sr isotopes in sediment cores from the Gulf of Cadiz and the Portuguese margin

Mediterranean Outflow Water (MOW) is characterised by higher temperatures and salinities than other ambient water masses. MOW spreads at water depths between 500 and 1500 m in the eastern North Atlantic and has been a source of salinity for the Atlantic Meridional Overturning Circulation in the North Atlantic. We used high-resolution Nd and Pb isotope records of past ambient seawater obtained from authigenic ferromanganese coatings of sediments in three gravity cores at 577, 1745 and 1974 m water depth in the Gulf of Cadiz and along the Portuguese margin complemented by a selection of surface sediments to reconstruct the extent and pathways of MOWover the past 23 000 years. The surface and downcore Nd isotope data from all water depths exhibit only a very small variability close to the present day composition of MOW but do not reflect the present day Nd isotopic stratification of the water column as determined from a nearby open ocean hydrographic station. In contrast, the Pb isotope records show significant and systematic variations, which provide evidence for a significantly different pattern of the MOW pathways between 20 000 and 12 000 years ago compared with the subsequent period of time.

Water temperature reconstructions based on paired Uk'37 and Tex86 records, and paired surface and subsurface Mg/Ca records

This dataset contains the collection of available published paired Uk'37 and Tex86 records spanning multi-millennial to multi-million year time scales, as well as a collection of Mg/Ca-derived temperatures measured in parallel on surface and subsurface dwelling foraminifera, both used in the analyses of Ho and Laepple, Nature Geoscience 2016. As the signal-to-noise ratios of proxy-derived Holocene temperatures are relatively low, we selected records that contain at least the last deglaciation (oldest sample >18kyr BP).

(Supporting Information) 14Cage plateau tuning of local Atlantic sediment cores

Modeling studies predict that changes in radiocarbon (14C) reservoir ages of surface waters during the last deglacial episode will reflect changes in both atmospheric 14C concentration and ocean circulation including the Atlantic Meridional Overturning Circulation. Tests of these models require the availability of accurate 14C reservoir ages in well-dated late Quaternary time series. We here test two models using plateau-tuned 14C time series in multiple well-placed sediment core age-depth sequences throughout the lower latitudes of the Atlantic Ocean. 14C age plateau tuning in glacial and deglacial sequences provides accurate calendar year ages that differ by as much as 500-2500 years from those based on assumed global reservoir ages around 400 years. This study demonstrates increases in local Atlantic surface reservoir ages of up to 1000 years during the Last Glacial Maximum, ages that reflect stronger trades off Benguela and summer winds off southern Brazil. By contrast, surface water reservoir ages remained close to zero in the Cariaco Basin in the southern Caribbean due to lagoon-style isolation and persistently strong atmospheric CO2 exchange. Later, during the early deglacial (16 ka) reservoir ages decreased to a minimum of 170-420 14C years throughout the South Atlantic, likely in response to the rapid rise in atmospheric pCO2 and Antarctic temperatures occurring then. Changes in magnitude and geographic distribution of 14C reservoir ages of peak glacial and deglacial surface waters deviate from the results of Franke et al. (2008) but are generally consistent with those of the more advanced ocean circulation model of Butzin et al. (2012).

Glacial North Atlantic: Sea surface conditions reconstructed by GLAMAP 2000

The response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology. Our new reconstruction of peak glacial sea surface temperatures (SSTs) in the Atlantic is based on census counts of planktic foraminifera, using the Maximum Similarity Technique Version 28 (SIMMAX-28) modern analog technique with 947 modern analog samples and 119 well-dated sediment cores. Our study compares two slightly different scenarios of the Last Glacial Maximum (LGM), the Environmental Processes of the Ice Age: Land, Oceans, Glaciers (EPILOG), and Glacial Atlantic Ocean Mapping (GLAMAP 2000) time slices. The comparison shows that the maximum LGM cooling in the Southern Hemisphere slightly preceeded that in the north. In both time slices sea ice was restricted to the north western margin of the nordic seas during glacial northern summer, while the central and eastern parts were ice-free. During northern glacial winter, sea ice advanced to the south of Iceland and Faeroe. In the central northern North Atlantic an anticyclonic gyre formed between 45° and 60°N, with a cool water mass centered west of Ireland, where glacial cooling reached a maximum of >12°C. In the subtropical ocean gyres the new reconstruction supports the glacial-to-interglacial stability of SST as shown by CLIMAP Project Members (CLIMAP) [1981]. The zonal belt of minimum SST seasonality between 2° and 6°N suggests that the LGM caloric equator occupied the same latitude as today. In contrast to the CLIMAP reconstruction, the glacial cooling of the tropical east Atlantic upwelling belt reached up to 6°-8°C during Northern Hemisphere summer. Differences between these SIMMAX-based and published U37[k]- and Mg/Ca-based equatorial SST records are ascribed to strong SST seasonalities and SST signals that were produced by different planktic species groups during different seasons.

Distribution of planktic foraminifera in surface sediments of the Atlantic Ocean

We present a data set of 738 planktonic foraminiferal species counts from sediment surface samples of the eastern North Atlantic and the South Atlantic between 87°N and 40°S, 35°E and 60°W including published Climate: Long-Range Investigation, Mapping, and Prediction (CLIMAP) data. These species counts are linked to Levitus's [1982] modern water temperature data for the four caloric seasons, four depth ranges (0, 30, 50, and 75 m), and the combined means of those depth ranges. The relation between planktonic foraminiferal assemblages and sea surface temperature (SST) data is estimated using the newly developed SIMMAX technique, which is an acronym for a modern analog technique (MAT) with a similarity index, based on (1) the scalar product of the normalized faunal percentages and (2) a weighting procedure of the modern analog's SSTs according to the inverse geographical distances of the most similar samples. Compared to the classical CLIMAP transfer technique and conventional MAT techniques, SIMMAX provides a more confident reconstruction of paleo-SSTs (correlation coefficient is 0.994 for the caloric winter and 0.993 for caloric summer). The standard deviation of the residuals is 0.90°C for caloric winter and 0.96°C for caloric summer at 0-m water depth. The SST estimates reach optimum stability (standard deviation of the residuals is 0.88°C) at the average 0- to 75-m water depth. Our extensive database provides SST estimates over a range of -1.4 to 27.2°C for caloric winter and 0.4 to 28.6°C for caloric summer, allowing SST estimates which are especially valuable for the high-latitude Atlantic during glacial times.