La Desirade Research Articles

Reliability of hemoglobin A2 value as measured by the Premier Resolution system for screening of β-thalassemia carriers.

Accurate quantification of hemoglobin (Hb) A2 is vital for diagnosing β-thalassemia carriers. This study aimed to assess the precision and diagnostic utility of HbA2 measurements using the new high-performance liquid chromatography (HPLC) method, Premier Resolution, in comparison to capillary electrophoresis (CE). We analyzed 418 samples, previously identified as A2A by CE, using Premier Resolution-HPLC. We compared the results, established correlations, and determined an optimal HbA2 cutoff value for β-thalassemia screening. Additionally, we prospectively evaluated the chosen cutoff value in 632 samples. Mutations in the β- and α-globin genes were identified using polymerase chain reaction (PCR) techniques and DNA sequencing. HbA2 levels were consistently higher with Premier Resolution, yet there was a significant correlation with CE in all samples (bias,-0.33; r, 0.991), β-thalassemia (bias,-0.27; r, 0.927), and non-β-thalassemia carriers (bias,-0.36; r, 0.928). An HbA2 cutoff value of≥4.0 % for β-thalassemia screening achieved 100 % sensitivity and 99.6 % specificity. Further validation yielded sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 97.3 , 99.8, 97.3, 99.8, and 99.7 %, respectively. We also identified a rare β-Hb variant, Hb La Desirade [HBB:c.389C>T], associated with β-thalassemia and co-inherited with a single α-globin gene. The Premier Resolution HPLC is a reliable and accurate method for routine β-thalassemia carrier screening, aligning with existing CE methods.

Clinical and Laboratory Features of Hemoglobin La Desirade Variant in Association with Sickle Cell and Alpha Thalassemia Genes.

Abstract 
 Hemoglobin La Desirade (Hb La Desirade) is an unstable hemoglobin variant characterized by amino acid Alanine (Ala) replacing Valine (Val) at position 129 (H7) in the beta chain. Hb La Desirade exhibits a decreased oxygen affinity and normal heme-heme interaction. Interestingly, on analysis by standard electrophoresis, it migrates in the same region as normal HbA, and HbA actually represents a combination of HbA and Hb La Desirade together. This variant was reported as compound heterozygous with other Hemoglobin variants such as HbS, HbC or beta thalassemia, and more recently with Southeast Asian ovalocytosis and Hb Louisville with varying clinical manifestations. Herein, we describe the clinical and laboratory findings in a number of Omani Arab families who presented to our service for various reasons, presenting with Hemoglobin La Desirade with sickle gene and alpha thalassemia. Our patients with Hb La Desirade trait, were clinically asymptomatic with no evidence of anemia. However when it is associated with other abnormal hemoglobin variants such as HbS, leading to sickle/La Desirade compound heterozygosity, there was mild anemia with significant degree of hypochromia and microcytosis. The most striking feature was that the levels of HbS and HbA were almost equal on HPLC, and these cases could be misdiagnosed as sickle cell trait (SCT). However, the levels of Hb S in these compound heterozygotes (40.4-45.9) were higher than normally seen for the diagnosis of SCT in this population.

Existing Territories and Formalization of Territorial Use Rights for Moored Fish Aggregating Devices: The Case of Small-Scale Fisheries in the La Désirade Island (France)

ABSTRACTMoored fish aggregating devices (MFADs) are used by small-scale fishers to access fish species difficult to harvest in large numbers. In the case of Guadeloupe (Caribbean area), the use of MFADs has increased considerably and this is causing congestion in these fishing areas and creating conflict between fishers. The aim of this article is to understand how informal fishing territories around the La Desirade Island were established and examine these territories through the lens of economic defendability theory. Results of semistructured interviews show that MFAD fishers display territoriality along MFAD tract lines forming quasi-privatized areas. Territoriality in this article is based on the following factors: the type of targeted resources, the cost of harvesting, the defending of territories, and the acknowledgment of territories by the fishing community. Conflicts and utilization of MFADs (overcapacity) have raised an opportunity to create co-managed legalized territorial use rights for fisheries.

Recognition of rare hemoglobin variants by hemoglobin A1c measurement procedures

BackgroundUnrecognized hemoglobinopathies can lead to measured hemoglobin A1c (Hb A1c) concentrations that are erroneous or misleading. We determined the effects of rare hemoglobin variants on capillary electrophoresis (CE) and HPLC methods for measurement of Hb A1c. MethodsWe prospectively investigated samples in which Hb A1c was measured by CE during a 14-month period. For samples in which the electropherograms suggested the presence of rare hemoglobinopathies, hemoglobin variants were identified by molecular analysis or by comparison with electropherograms of known variants. When sample volume permitted, Hb A1c was measured by 2 HPLC measurement procedures and by boronate affinity HPLC. ResultsHb A1c was measured by CE in 33,859 samples from 26,850 patients. 15 patients (0.06%) were identified as having rare hemoglobinopathies: Hbs A2 prime, Agenogi, Fannin-Lubbock I, G Philadelphia, G San Jose, J Baltimore, La Desirade, N Baltimore, Nouakchott, and Roanne. Among 6 of these samples tested by 2 ion-exchange HPLC methods, the rare Hb was detected by both HPLC methods in only one sample, and none were detected by boronate affinity HPLC. The mean of the Hb A1c results of 2 HPLC methods differed from the result of the CE method by 0.7–2.2% Hb A1c in samples with variant hemoglobins versus <0.2% Hb A1c in samples without variants. ConclusionMeasurement procedures differ in the ability to detect the presence of rare Hb variants and to quantify Hb A1c in patients who harbor such variants.

Low oxygen saturation and severe anemia in compound heterozygous Hb Louisville [β42(CD1)Phe→Leu] and Hb La Desirade [β129(H7)Ala→Val

ABSTRACTObjective: To investigate the cause(s) of a Thai male proband presenting low oxygen saturation by pulse oximetry (SpO2) and severe anemia.Methods: As Hb variant was suspected, Hb typing was determined by high-performance liquid chromatography and capillary electrophoresis, and subsequently Hb variant was identified by DNA sequencing. Complete blood counts were performed using automated blood cell counter and oxygen saturation was measured by pulse oximetry.Results: Proband was compound heterozygous for Hb Louisville [β42(CD1)Phe→Leu] and Hb La Desirade [β129(H7)Ala→Val]. Of the proband’s two sons, one was compound heterozygous for Hb Louisville and Hb E and the other for Hb La Desirade and Hb E. The former son had similar clinical features and laboratory findings with those of the proband while the latter showed had no abnormal clinical manifestations.Conclusion: This the first report of compound heterozygosity of Hb Louisville and Hb La Desirade in an individual of Southeast Asian ethnicity. Hb variant identification is crucial for genetic counseling and appropriate treatment in regions where hemoglobinopathies are common.

A new species of skink from the Guadeloupe Archipelago (Squamata, Mabuyidae, Mabuya)

A new species of lizard of the genus Mabuya is described from a small island in the Guadeloupe Archipelago: Terre de Bas, Iles de la Petite Terre. Mabuya parviterrae sp. nov. is allied with the other four species of Mabuya from Guadeloupe. However, it differs in scalation, coloration, and (where available) DNA sequence. Of the nine named species in the genus, only M. dominicana (from Dominica), M. desiradae (from La Desirade), nd M. parviterrae sp. nov. have escaped decimation and possible extinction by the Small Indian Mongoose, Urva auropunctata. The latter two species of skinks are critically endangered, being threatened by the Black Rat (Rattus rattus) and degraded habitat that has not recovered from early land use. The Petite Terre Skink probably has one of the smallest distributions of a vertebrate species. The species consists of approximately 50 individuals living primarily in a dry stone wall of less than 500 square meters in extent.

Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

The Karukera spur is an easternmost submerged rise of the Lesser Antilles fore-arc in the Guadeloupe archipelago, culminating about 4000 m above the fore-arc basin 150 km west of the deformation front. The analysis of 3500 km 2D high-resolution multichannel seismic reflection and multibeam bathymetric data, and the study of 14 core samples, allow for the first time to reconstruct its sedimentary anatomy and tectonic evolution. Seven seismic units (US1 to US7) are evidenced, organised into four major depositional sequences separated by erosional surfaces. Units US1 to US4 thicken to the south-southeast on the spur. The sedimentary deposits rest upon a deeply eroded metamorphic basement of the Caribbean Plate as in La Desirade Island. Sequence 1 (units US1 and US2) remains unknown in its lower part because it does not outcrop. Its upper part comprises early Miocene shallow water carbonates. Sequence S2 (Unit US3) only comprises an upper Miocene transgressive systems tract deposited into basinal environment. It is bounded by major erosional surfaces SB2 and SB3. Sequence 3 (US4 to US6) is Zanclean to Pleistocene. It is dominantly composed of shallow water, reefal deposits. Sequence 4 corresponds to recent deposits. The Karukera spur experienced three main extensional episodes with alternations between uplift and subsidence periods. Uplifts are responsible for emersions and erosions. Subsidence severely drowned shallow water deposits. The first extensional episode led to the formation of horsts and grabens in the basement, prior to early Miocene deposits. The second extensional episode occurred during upper Miocene, in accordance with data in surrounding islands. The third tectonic episode developed since Calabrian. Noticeable is the constant reactivation of N130°–N150°, N150°–N180° and N40° trending faults since early Miocene and the neoformation of E–W trending faults since Calabrian. Our results suggest that at the latitude of Guadeloupean archipelago the Lesser Antilles subduction zone is an erosional margin because of the successive sweepings of the Santa Lucia then Tiburon Ridges.

Pliocene to Pleistocene vertical movements in the forearc of the Lesser Antilles subduction: insights from chronostratigraphy of shallow-water carbonate platforms (Guadeloupe archipelago)

An integrated stratigraphic study was conducted on the shallow water carbonate platforms of the Guadeloupe archipelago to refine the tectonic evolution of the Lesser Antilles forearc. The carbonate platforms are now dated to the Zanclean–Calabrian interval, and their demise occurred between 1.5 and 1.07 Ma. The precise chronostratigraphy allows dating of the main extensional tectonic events since the late Miocene. An initial episode occurred during the late Miocene, related to the reactivation of inherited N130°E-trending shear zones, and led to the emergence of most parts of the forearc. Subsequently, Zanclean to early Piacenzian carbonate platforms developed in association with a general subsidence of the forearc. During the late Piacenzan, a second extensional episode occurred. At this time La Désirade underwent major uplift and emergence whereas most of the forearc remained submerged. Prior to 1.07 Ma, a third north–south extensional episode occurred and led to the final demise of the carbonate platforms. Thus the forearc was characterized by general subsidence since the early Pliocene interrupted by three main extensional episodes and related differential uplifts. This suggests that the Lesser Antilles subduction is probably erosive north of latitude 15°N since c . 5 Ma, related to aseismic ridge subduction. Supplementary data: Planktonic foraminiferal assemblages, calcareous nannofossil taxa associations, 40 Ar/ 39 Ar geochronological data and palaeomagnetic data are available at www.geolsoc.org.uk/SUP18724 .

Index Pteridophytorum Guadalupensium or a revised checklist to the ferns and club mosses of Guadeloupe (French West Indies)

Recent revision of the fern diversity of the French Caribbean island of Guadeloupe and its dependencies (Marie Galante, Les Saintes and La Desirade) resulted in the listing of 292 native ferns and club mosses in 28 families and 88 genera, of which eight ferns are endemic to Guadeloupe and 20 taxa are only recorded from the Lesser Antilles. Additionally, 21 species have recently been found to be naturalized. Nineteen new combinations are made and a new hybrid is described. Many types from the Fee collection have been reassessed and a number of names are lecto- or neotypified. Studied specimens are cited and localities are provided. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 213–277.

Small Islands, Large Settlements: Archaeology at Les Îles de la Petite Terre, Guadeloupe, F. W. I.

Introduction Between 1998 and 2000, three archaeological fieldwork campaigns were carried out at the islands of Petite Terre, F.W.I., by teams of archaeologists from Leiden, the Netherlands. The investigations, directed by the author, then working at Leiden University, were part of a study that was designed to investigate social organisation and interaction through the study of site (De Waal, 2006). For this study, a micro-region was selected, consisting of the Pointe des Châteaux peninsula of Guadeloupe and the islands of La Desirade and Petite Terre (Figure 1). This essay focuses on the pre-Columbian occupation of the small islands of Petite Terre. Setting Les Iles de la Petite Terre, as the islands are called officially, belong to the Lesser Antilles. They will be referred to as Petite Terre, as is common practice on Guadeloupe. Petite Terre is part of the French department of Guadeloupe and administratively it belongs to the municipality of La Desirade. Petite Terre is situated at approximately 12 km south of La Desirade and at 7.5 km south-east of Pointe des Châteaux. Petite Terre consists of two small calcareous islands: Terre de Haut and Terre de Bas (Figure 2). Terre de Bas measures 2.5 km by 600 m, while Terre de Haut measures only 1.1 km by 200-300 m. The islands of Petite Terre are flat west-east oriented islands that originally consisted of one elevated coral plateau. They show a general inclination in a west/northwestern direction, which is the result of tectonic processes (DIREN, Guadeloupe, 1994, 6). A 150 m wide channel, which is 7 m deep at most and is enclosed on the eastern side by an impressive reef barrier, separates the islands. The islands are almost completely enclosed by coral reefs (DIREN Guadeloupe, 1994, 6). Abrasion of these reefs by sea action has created sand beaches that dominate the low northern and western parts of Terre de Bas. These sandy areas are easily influenced by wind and sea action. They are characterised by dynamic dune formations that border a depression that nowadays contains salinas (Conservatoire du Littoral, 1997, 8; DIREN Guadeloupe, 1994, 6). At high seas, for example during hurricanes, the easternmost of these salinas is in open connection to the sea. Therefore, it is always filled with water, whereas the two others are periodically dry (Rousteau, 1995, 8). The more elevated south and east coasts of Terre de Bas are rocky with limestone outcrops, as is most of Terre de Haut. Coastal dynamics, mainly caused by wave action, have drastically altered the coasts of Petite Terre since pre-Columbian times. Coastal areas with reef-passages or which lack reef protection have been subjected to heavy coastal erosion. Tropical storms and hurricanes greatly accelerate erosion processes. Areas with salinas and sand beaches are the least stable and most vulnerable to erosion. The northern and western coasts of Terre de Bas are particularly unstable with large parts of the beach and the dunes eroding rapidly (Figure 3). This is evidenced by steep, almost vertically eroded, slopes of the dunes (personal observation 1997-2000). Although a lot of the sandy coast disappears, an important part of the sand is displaced inland as well. The dunes on Petite Terre, which are relatively young and which appear to be shifting rapidly, are characterised by pioneer vegetation. The salinas are gradually being filled up with sand, a process that is clearly visible at the easternmost of the three principal salinas of Terre de Bas (Rousteau, 1995, 8). Possibilities of obtaining fresh water on Petite Terre appear limited, as most fresh water sources are not currently visible from the surface. Many of these are fresh water lenses, or aquifers, situated between chalky layers in the subsurface, or floating on saline groundwater as a result of their lower density. This phenomenon, fed by rainfall, has also been reported for other flat limestone islands, for example Barbuda (Waiters, 1980, 64). …

The Jurassic-Cretaceous boundary: new data from North America and the Caribbean

The Jurassic-Cretaceous boundary is the most problematic of all Phanerozoic system boundaries. Its defini- tion is obscured by almost imperceptible faunal and floral change, nomenclatural problems resulting from the poor defini- tion of its bounding stages, the over reliance of calpionellids for correlation, and the provinciality of ammonite zones in the European type area. The unfortunate decision of ammonite stratigraphers to use Calpionella Zone B to mark the base of the Berriasian set back the resolution of the Jurassic-Cretaceous boundary problem by thirty-five years in Europe, North America, and elsewhere. In this report a more detailed radiolarian zonation for the Upper Jurassic is introduced. The ra- diolarian biostratigraphy has been integrated with that of the North American ammonite, Buchia, calcareous nannofossils, and calpionellids as well as with new and existing U-Pb geochronometry. Investigations focused on uppermost Jurassic to lowermost Cretaceous successions in central Mexico, Baja California, California, and the West Indies have recognized four new subzones in both radiolarian Zones 2 and 4. Pillow basalt at La Desirade dated at 143.734ma ± 0.060ma [0.042%] (U-Pb zircon age on coeval plagiogranite) is intercalated with red ribbon chert containing an upper Subzone 4 beta2 radiolarian as- semblage with corporeal taxon Neovallupus spp. This horizon likewise occurs in Mexico, where it can be directly related to ammonite-bearing strata occurring slightly below the boundary between Imlay's Kossmatia-Durangites and Substeuero- ceras-Proniceras assemblages, and can be recognized in Argentina and Antarctica as well. The composite data from the North American record indicate that the European calpionellid biozones are diachronous between Europe and the Western Hemisphere. The boundary between Zone 4, Subzone 4 alpha, and Zone 5, Subzone 5A, which corresponds to the tradi- tional Jurassic-Cretaceous boundary, is well represented at Grindstone Creek in the California Coast Ranges in the upper part of the Buchia sp. aff. B. okensis Zone. In view of our findings, however, it also may be desirable to consider two other alternatives for the placing the Jurassic-Cretaceous boundary: one at the base of new Radiolarian Subzone 4 alpha, and the ammonite Substeuerocas-Proniceras assemblage, and the other at the base of the Valanginian. The traditional boundary horizon as well as the two alternatives can all be related to new and existing U-Pb geochronometric data. Nomenclatural problems surrounding formational units in the Mexican Upper Jurassic have been addressed. Four new members for the La Caja Formation; two new members for the Taman Formation; and one new formational unit, the Santa Rosa Formation have been introduced.

Global rockfalls risk management process in ‘La Désirade‘ Island (French West Indies)

The Island of ‘La Desirade‘ is severely affected by rock falls. One house located in the area of ‘Le Souffleur‘ was partly destroyed by blocks in 1997, with two people injured. About 50 people still live under a dangerous cliff along the road from Beausejour to Baie-Mahault, the two main villages of this eastern end of Guadeloupe archipelago. The first solution proposed by the state based on relocation of few houses was faced to population hostility. Solutions had to be reshaped and designed based on a global assessment of the different hazards affecting the Island (earthquakes, cyclones, flooding), on protection works taking into account the fact that French regulation prohibits new constructions behind protection fences, and on global and local land-use development. Risk management process has included technical analysis, social behaviour, cultural heritage of building and development, responsibility and regulation, short-term and long-term financing, land-use development strategy as well as information and communication. The solutions that are now being implemented seem to give satisfaction to all the partners. This example of landslide risk management carried out in La Desirade is discussed in this paper.

Shattered Pasts, Fractured Selves: Trauma and Memory in Desirada

Maryse Conde's published in 1997, chronicles the lives of three generations of women, Nina, Reynalda and Marie-Noelle Titane. The story begins shortly before 1928 with the birth of Nina in la Desirade, Guadeloupe, and ends in 1990s Boston with the story of Marie-Noelle. The lives of all three women are marked by separation from home, rape and sexual abuse. In this essay I shall attempt to analyze the intergenerational impact of these traumatic events on the lives of the characters. Such analysis implies a theoretical exploration of the nature of trauma and of the structure and functioning of memory. In this, I am inspired by the works of Cathy Caruth and Dori Laub, M.D., whose work in the field of trauma theory has contributed to the re-examining of these questions that originate in psychoanalysis within the framework of literature. Nina, Reynalda and Marie-Noelle share certain events in their lives that have made indelible mark on their being. These events are characterized by their profoundly traumatic nature. All three women are torn from the place of their birth, where, despite the harsh conditions, they feel rooted in a sense of well-being and belonging. Nina is raped and Reynalda is either molested or raped, or indeed both. Marie-Noelle escapes the violence of tape, but becomes a witness to a form of insidious sexual violence in her role as watchdog for her friend's wretched sexual activity, which is a heart-breaking attempt at procuring the necessities of everyday life. Furthermore, all three women grow up in the shadow of the missing father and, perhaps more significantly, in the shadow of the missing mother. For in the case of Reynalda and Marie-Noelle, the mothers are emotionally absent from their lives, while in the case of Nina, the mother has died. The looming presence of Il Lago di Como signals and conceals unknowable truth about the history of the three women. It is the most significant site for the transmission of memory, as their individual encounters with it mark each woman deeply. The pathology of these three women is first and foremost characterized by a rupture in the continuity of their history, a fissure in their being, a wound on their psyche, a trauma. The American Psychiatric Association defines trauma as an event outside the range of human experience. And indeed, all three women experience such event, not just once, but repeatedly. All three are traumatized by having been wrested away from their homes, from the land of their birth, a place to which all show a great attachment despite the harshness of their life there. Let us look at three passages uttered by Nina, Reynalda and Marie-Noelle, respectively: Nina indulges in the following reflection, Quand je reflechis, je m'apercois que ces annees-la n'ont pas ete les plus dures de ma vie malgre le travail et la faim. J'avais ma Bonne-Maman [ ... ] Ma Bonne-Maman qui ne parlait pas beaucoup, mais qui avait toujours une douceur pour moi, cachee dans son corsage, des topinambours, un sucre a coco tete-rose, un nougat pistache. These memories are echo of similar thoughts revealed by Reynalda, C'est a la Desirade que je suis nee. Les gens de la Guadeloupe ont une mauvaise idee de la Desirade a cause des sacripants et des lepreux qu'on y envoyait dans le temps et aussi, parce que rien n'y pousse. [ ... ] Mais pour moi, petite fille, c'etait vraiment Desirada, ile desiree surgie sur la mer devant les yeux des marins de Christophe Colombe apres des jours et des jours. Je possedais tous ses recoins. Je respirais son odeur quand le soleil qui l'a chauffee toute la journee repose enfin sa tete au fond de l'eau. Je pouvais soulever une roche et nommer avec certitude le nom de l'insecte cache en dessous. Je connaissais ses razye. [ ... ] Elle (Nina) a donne un tour de cle a la porte et nous voila parties. Moi, j'etais a l'agonie. …

Ophiolites, the Sierra Nevada, “Cordilleria,” and Orogeny along the Pacific and Caribbean Margins of North and South America

Ophiolites are major expressions of orogeny; they are dominantly oceanic crust and mantle emplaced by collision of a mantle-rooted thrust (subduction zone) with a continental margin or island arc. Ophiolite nappes thus represent remnants of lithospheric plates; their basal thrusts (fossil subduction zones) intrinsically cannot be balanced; their displacements are unknown but very large. Two major belts of Mesozoic ophiolites and related island-arc complexes extend along the western and Caribbean margins of the Americas from Alaska to Ecuador. An eastern belt (e.g., Stikinia-Intermontane superterranes, Canada, United States; rocks of western Baja Californa and the Guerrero terrane, Mexico; ophioliticand related rocks of Guatemala, Cuba, Hispaniola, Puerto Rico, and La Desirade; Cordillera de la Costa, Venezuela; and the Cordillera Central, Colombia) was an active island-arc complex in the Early to Middle Jurassic and was emplaced in Middle Jurassic-Cretaceous time. A western belt (e.g., the Wrangellia/Insular superterrane of Canada and United States; Choco-Chortis blocks of Central America; Cordillera Occidental (Pinon) of Colombia and Ecuador) experienced activity during the Jurassic-Cretaceous and was emplaced during Late Cretaceous-Tertiary time. These relations inspire an outrageous hypothesis that in Middle to Late Mesozoic time, a separate intra-oceanic plate similar to the present Philippine plate, herein named “Cordilleria,” was separated by active island-arc complexes from the American and Farallon/Kula plates to the east and west, respectively. Basement rocks of the Colombian, Venezuelan, and Yucatan basins may represent remnants of “Cordilleria.” Convergence and collision of “Cordilleria” and its island-arc margins with the American continents were major factors in western American and Caribbean orogenic development. The Mesozoic tectonic history of the North American Cordillera, with its conflicting sinistral and dextal motions at varying locations and times, suggests a model involving a rigid-plastic continuum approximation using slip-line field theory, as successfully applied to the Indian-Eurasian collision. Complex evolution of the northern Sierra Nevada and its surroundings may reflect such tectonics. Direct contact between the Kula/Farallon plates and North America may not have occurred until Late Cretaceous time.

Paleogeography of Jurassic fragments in the Caribbean

Jurassic rocks of the Caribbean are a sampling of 100 million years of Farallon Plate history with fragments originating at diverse paleolatitudes and from varied tectonic settings. Fragments with clear paleogeographic signatures are components of the basement complexes of Duarte in Hispaniola, Bermeja in Puerto Rico and La Désirade off Guadeloupe. Paleolatitudinally sensitive radiolarian faunas document origination of Duarte as equatorial, La Désirade as higher latitude, and various Bermeja cherts as both equatorial and higher latitude. Red ribbon chert of Duarte and Bermeja of the same age, physical appearance, and lithological association are probably dismembered components of the same slab of Pacific crust. La Désirade red ribbon chert is slightly younger than the Duarte and Bermeja red ribbon chert and was deposited at higher latitude. Bermeja tuffaceous chert is also of higher latitude and probably had an arc‐proximal origin. On the basis of modeled plate trajectories in the Pacific, the origin of various cherts from different paleolatitudes that end up in the same location requires different arrival times at the trench between North and South America. Based on radiolarian paleobiogeography plus indications of origin at a spreading ridge and ignoring the poorly constrained, modeled trajectories for the Late Jurassic, at least one of the higher latitude fragments may have originated in the southern hemisphere. The accumulation of multifarious chert, greenstone, and other ocean floor components was accomplished by offscraping strata transported to the subduction zone along the eastern Pacific margin and warehousing this material in an accretionary complex prior to entry of the Caribbean Plate into the gap between North and South America.

Social values and population structure: Phenotype and genealogies in La Désirade (West Indies)

In a small population (La Desirade, West Indies) with few internal socio-economic differences, the «white» segment survive on the basis of long-term assortative mating. This study compares the genealogies for one hundred and forty years, with phenotypical markers used in the population to define «racial» identity of individuals. Physical appearance, acting as an isolated factor, is able to maintain endogamy and to ensure the survival of a segment of the population without any black admixture. The social values do not produce the same effect among people of African origin. Genetic structure reflects these values and the genealogical pattern is able to assert their impact on the mating pattern.

Hemoglobin La Desirade alpha A2 beta 2 129 (H7) Ala----Val: a new unstable hemoglobin.

Hemoglobin La Desirade is a new unstable hemoglobin variant arising from the substitution of beta 129 (H7) Ala for Val. Hb La Desirade exhibits a low oxygen affinity and normal heme-heme interaction. The variant was found in two unrelated black families in association with Hb S, Hb C or beta o thalassemia.

Donnees sur la structure de l'arc insulaire des Petites Antilles, entre Ste-Lucie et Anguilla

Geological and geophysical data were collected during a marine geological cruise (ARCANTE 1) carried out in 1977–1978 between St. Lucia and Anguilla, corresponding to about two thirds of the length of the Lesser Antilles archipelago. They allow of a reconsideration of the structural framework of this island arc. Considered as a whole, the Lesser Antilles ridge is characterized by a pattern contrasting sharply between its northern and southern halves. The major discontinuity axis runs to the south of the Guadeloupe archipelago. The basement of the northern half is supposed to be mainly Mesozoic and is connected with the evolution of the Greater Antilles, whilst the southern half was generated only since the Eocene. The NE flanks of the Lesser Antilles ridge are steep and dissected by large submarine valleys such as the Desirade sea trough; their recent sedimentary cover (post-lower Miocene) is lacking or very poor, enabling the outcropping of older formations: volcanic Mesozoic basement (around la Desirade), Upper Cretaceous, Eocene and Oligocene sediments. Conversely, the NW flanks are gently sloping and are draped by a rather thick overburden of Plio-Pleistocene deposits. To the south, the steep SW flanks are covered with a moderate thickness of recent sediments and display characteristics contrasting with those of the SE flanks, facing the Barbados accretionary prism. From the south up to Martinique, there is only one volcanic ridge, of Eocene to Present age. To the north of Martinique this ridge splits into two axes. The submarine landmarks of these two arcs have been disclosed during the present survey. The eastern one, or outer arc, shows a row of seamounts and islands often marked by strong magnetic (Dien Bien Phu Bank, Marie-Galante, Agouti Bank) or heavy gravimetric (Marie-Galante, Grande-Terre) anomalies. This outer arc was superimposed on the pre-Eocene basement, and is expressed in the Eocene and Oligocene volcanic terrains cropping out in the islands of Antigua, St. Bartholomew, St. Martin and Anguilla which rise from the wide northern insular shelves. A major (ca. 70 km) interruption in the continuity of this axis takes place between Dien Bien Phu Bank and Marie-Galante. La Desirade and Barbuda islands, although pertaining to the “Limestone Caribbees”, are not included in the outer arc. The western — or inner — arc, made up of upper Miocene to Present volcanics, begins with Dominica island and terminates at Luymes Bank, but an interruption of about 50 km is to be noted between Basse-Terre and Montserrat. The outer and inner arcs are separated by the narrow (ca. 50 km) and elongated (ca. 250 km) Kallinago depression. This intra-arc trough is generally filled by less than 1 km of recent sediments and is subdivided into three smaller basins; it was not initiated by extensional rifting related to back-arc spreading, as was previously assumed. It is possible that from Martinique to Guadeloupe an intermediate arc was in activity during the Miocene. Data from exploratory oil surveys provide some new insights into the geology and the structure of the wide Saba Bank, located to the west of the inner arc and near the northern end of the archipelago. Its volcanic substratum is of Upper Cretaceous—Paleocene age and is part of the pre-Eocene basement of the northern Lesser Antilles. The general characteristics of the NE flanks of the Lesser Antilles ridge may indicate some tilting toward the west of the northern part of the island arc. This may be ascribed to the arrival of Atlantic fracture zone ridges (Barracuda and Tiburon) in the subduction zone, during the Miocene. This event could explain the jump of the volcanic line from the outer to the inner arc.

La Desirade Island (Lesser Antilles) revisited: Lower Cretaceous radiolarian cherts and arguments against an ophiolitic origin for the basal complex

La Desirade Island in the Guadeloupe archipelago is a keystone of the structural framework of the Lesser Antilles island arc. Hypothetical ophiolitic series and wide discrepancy in the radiometric datings of its igneous basement have raised considerable debate concerning the structural significance of this island and the geodynamic constraints for the Caribbean plate. Recent detailed field work leads to a reconsideration of the problem. The volcanic basement of La Desirade can be subdivided into three independent units. The cherts interbedded in the unit 2 basalts contain Hauterivian-Barremian radiolarians that represent the oldest biostratigraphic assemblage found in the Lesser Antilles. This affirms the Jurassic radiometric age of the unit 1 trondhjemite outcrop. Observations and analyses allow us to discard the concept of an ophiolitic origin for La Desirade, whose basement was generated, like the northern half of the Lesser Antilles arc, by island-arc processes during the Mesozoic.

Geochronologic and isotopic study of the La Désirade island basement complex: Jurassic oceanic crust in the Lesser Antilles?

La Desirade, a small island east of Guadeloupe, is underlain by the only exposed pre-Tertiary basement rocks in the Lesser Antilles. The basement complex comprises spilitic and keratophyric flows and pillow lavas (with interbedded and overlying radiolarian cherts), swarms of mafic to silicic dikes, and subjacent plagiogranite. These features, and the absence of carbonates, terrigenous clastic sediments, or tuffaceous sediments from the complex indicate that it developed in a deep marine environment beyond the reach of terrigenous sedimentation or emergent island arc pyroclastic deposition. Previous workers have suggested that the Desirade basement complex originated either as oceanic crust or during an early (tholeiitic) stage of island arc growth. The isotopic compositions of Sr and Pb from the complex, and previously reported rare earth data (Johnston and Schilling, 1974) do not provide a clear distinction between these two possibilities. Nor does the presence of siliceous keratophyre in the complex rule out an oceanic crustal origin-such rocks are common in well studied ophiolites that originated as oceanic crust. Hence we turn to the age relationships of the complex, the surrounding ocean floor, and adjacent island arcs in an attempt to resolve this problem. The age of the complex strongly supports an oceanic crustal (ophiolitic) origin. The ages of zircons and a previously reported K-Ar age indicate that the complex is 145±5 m.y. old. The complex predates the next oldest volcanic rocks of the Lesser Antilles arc by ca. 110 m.y., and the oldest known rocks of the Aves Ridge, a possible Mesozoic precursor of the Lesser Antilles arc, by 50–60 m.y. This makes it unlikely that the Desirade complex is related to an early phase of either of these arcs. Instead, the age of the complex falls in the range of ages expected for oceanic crust in the vicinity of the Lesser Antilles prior to the development of any subduction zone and resulting arc. Thus we interpret the Desirade complex to be an uplifted segment of oceanic crust that represents the basement on which the later island arcs grew: first the Aves Ridge, an arc that was active in middle to late Cretaceous time (but whose exact mode of origin is enigmatic, and is considered in four alternate tectonic models), then the Eocene to Recent Lesser Antilles arc.