Abstract In this paper we present and discuss new investigations performed on both the magmatic basement and the sedimentary formations of La Désirade. We report structural and sedimentary evidences for several episodes of deformation and displacement occurring prior to the present day tectonics. The main faults, respectively N130 ± 10°, N040 ± 10° and N090 ± 10°, previously considered as marker of the current tectonic regime corresponds to reactivated tectonic structures developed first during late Cretaceous compression and second during Pliocene to early Pleistocene extension. We demonstrate also the importance of late Pliocene-early Pleistocene and middle-late Pleistocene vertical movements in this part of the Lesser Antilles fore-arc as well as the role of compressive tectonics in the over thickened character of the arc basement in the Guadeloupe archipelago.
The late Miocene sediments of the Tyrrhenian ODP Site 654 encompass a deepening sequence which begins with glauconite shallow water sands followed by a rapid transition to deep water sediments and culminates with dolomitic mudstones associated with Messinian evaporites. The sequence compares well with the so-called Sahelian cycle and with post-orogenic cycles recognized in peninsular Italy and Sicily. The studied interval, consisting of 55 m thick nanno fossil oozes, belongs to the Globorotalia suterae subzone and lower part of the Globorotalia conomiozea Zone, indicat ing late Tortonian and early Messinian age, respectively. Biomagnetostratigraphic correlation assigns the Tortonian/ Messinian boundary an age of 6.44-6.45 Ma. In addition, six main events have been recognized, based on the range of keeled globorotaliids and coiling direction changes of keeled and unkeeled globorotaliids, which have been correlated to the geomagnetic time-scale. Comparison with North Atlantic sites and land sections of the Guadalquivir basin and northern Morocco provides good correlations with the events documented in these areas. In particular, Event IV, which predates the FO of Globorotalia conomiozea, may be used to recognize the Tortonian/Messinian boundary in extraMediterranean areas where G. conomiozea is missing. Variations in the distribution of different species of Globigerinoi des are related to changes in the surficial marine environment. Although no clear trends can be recognized on the oxy gen and isotope records of Globigerinoides obliquus, the parallelism between the occurrence of low salinity spe cies (G. sacculifer) and peaks of low 5180 values, as well as that of normal salinity species (G. obliquus) and peaks of high 5180 values, suggests strong local changes of environmental conditions. The high amplitude of the fluctuations of 5180 values suggests important variations in the salinity of the Tyrrhenian Sea, related to a rapidly changing water bud get. The major feature of the isotope record is a large decrease between 7.0 and 6.95 Ma, which therefore pre dates the 6.2 Ma global carbon shift.
Abstract Pliocene and Pleistocene deposits from Grande‐Terre (Guadeloupe archipelago, French Lesser Antilles) provide a remarkable example of an isolated carbonate system built in an active margin setting, with sedimentation controlled by both rapid sea‐level changes and tectonic movements. Based on new field, sedimentological and palaeontological analyses, these deposits have been organized into four sedimentary sequences (S1 to S4) separated by three subaerial erosion surfaces (SB0, SB1 and SB2). Sequences S1 and S2 (‘Calcaires inférieurs à rhodolithes’) deposited during the Late Zanclean to Early Gelasian (planktonic foraminiferal Zones PL2 to PL5) in low subsidence conditions, on a distally steepened ramp dipping eastward. Red algal‐rich deposits, which dominate the western part of Grande‐Terre, change to planktonic foraminifer‐rich deposits eastward. Vertical movements of tens of metres were responsible for the formation of SB0 and SB1. Sequence S3 (‘Formation volcano‐sédimentaire’, ‘Calcaires supérieurs à rhodolithes’ and ‘Calcaires à Agaricia’) was deposited during the Late Piacenzian to Early Calabrian (Zones PL5 to PT1a) on a distally steepened, red algal‐dominated ramp that changes upward into a homoclinal, coral‐dominated ramp. Deposition of Sequence S3 occurred during a eustatic cycle in quiet tectonic conditions. Its uppermost boundary, the major erosion surface SB2, is related to the Cala1 eustatic sea‐level fall. Finally, Sequence S4 (‘Calcaires à Acropora’) probably formed during the Calabrian, developing as a coral‐dominated platform during a eustatic cycle in quiet tectonic conditions. The final emergence of the island could then have occurred in Late Calabrian times.
Abstract In this study, we investigate the Lesser Antilles forearc basin, focusing on the late Pliocene to Pleistocene sedimentary archives in order to track the occurrence of extreme events triggered by enhanced subduction‐related tectono‐volcanic activity. We identify late Piacenzian deposits covering a major regional erosional surface, displaying sedimentary dykes and large marine boulders embedded in a mixed continental–marine matrix, characteristic of tsunamites. We interpret this episode of platform emersion and the successive cataclysmic deposits as resulting from enhanced tectonic activity at the interface of the subduction zone, synchronous with the initiation of the Lesser Antilles volcanic arc. We then discuss the implications in terms of the mechanical behaviour of the Lesser Antilles subduction zone.
Ten surface samples of Albian to Danian strata from Madagascar have been examined for planktonic foraminifera, calcareous nannoplankton and palynomorphs including dinoflagellates. The stratigraphical results based on these micropaleontologic groups have been compared with data based on megafossils, mainly ammonites. In general, the conclusions are closely similar and the differences do not exceed more than half a stage. Special attention is paid to the relationship of Madagascar to the microfloral provinces established for the mid-Cretaceous. Madagascar may be assigned to the Gondwana paleophytogeographic province, probably close to the northern boundary and transitional to the African-South American province. Micropaleontology of Albian to Danian strata in Madagascar
Other| September 01, 1985 Utilisation des foraminiferes planctoniques dans la paleooceanographie de la Tethys au Cretace R. Anglada; R. Anglada Author Univ. provence, lab. stratigr. paleoecol., Marseilles 13331, France Search for other works by this author on: GSW Google Scholar A. Randrianasolo A. Randrianasolo Author Search for other works by this author on: GSW Google Scholar Author and Article Information R. Anglada Author Univ. provence, lab. stratigr. paleoecol., Marseilles 13331, France A. Randrianasolo Author Publisher: Société Géologique de France First Online: 03 Mar 2017 Online Issn: 1777-5817 Print Issn: 0037-9409 GeoRef, Copyright 2012, American Geosciences Institute. Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique, Vandoeuvre-les-Nancy, France Bulletin de la Société Géologique de France (1985) I (5): 747–755. https://doi.org/10.2113/gssgfbull.I.5.747 Article history First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R. Anglada, A. Randrianasolo; Utilisation des foraminiferes planctoniques dans la paleooceanographie de la Tethys au Cretace. Bulletin de la Société Géologique de France 1985;; I (5): 747–755. doi: https://doi.org/10.2113/gssgfbull.I.5.747 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin de la Société Géologique de France Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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 .
