Jacques Bertaux

Institut de Recherche pour le Développement

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Hilaire Elenga

Marien Ngouabi University

Annie Vincens

Centre de Recherche et d’Enseignement de Géosciences de l’Environnement

Dominique Schwartz

Université de Strasbourg

Louis Martin

Team (Italy)

Denis Wirrmann

Institut de Recherche pour le Développement

Abdelfettah Sifeddine

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

François Soubiès

Institut de Recherche pour le Développement

Marie‐Pierre Ledru

Université de Montpellier

Michel Servant

Institut de Recherche pour le Développement

Isabelle Farrera

Agropolis International

Cooperative Institutions

Centre National de la Recherche Scientifique

Institut de Recherche pour le Développement

Sorbonne Université

Université Paris Cité

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Laboratoire des Sciences du Climat et de l'Environnement

Centre de Recherche et d’Enseignement de Géosciences de l’Environnement

Institut des Sciences de la Terre

Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques

Instituto de Geociencias

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Late Holocene Paleoclimatic Changes in Western Central Africa Inferred from Mineral Abundance in Dated Sediments from Lake Ossa (Southwest Cameroon)

Quaternary Research (2001)

Denis Wirrmann Jacques Bertaux Alice Kossoni

Abstract Minerals derived from catchment soils were determined using FTIR spectroscopy in the well-dated core OW4 from Lake Ossa, a lowland rainforest area in Cameroon. This quantification provides a hydrologic record indicating that the magnitude of runoff events, and by inference, rainfall pattern, has varied during the Late Holocene. The comparison between minerogenic inputs and vegetation changes improves the understanding of the inferred climate dynamics. Since at least 5400 cal yr B.P., the paleomonsoon rainfall intensity decreased, as shown by a general decrease in mineral fluxes. This observation is consistent with a gradual weakening of the boreal summer insolation in tropical latitudes. However, the major vegetational change lags behind the onset of the decrease in mineral fluxes. From 2800 to ca 1000 cal yr B.P., the forest receded: the amount of rainforest taxa decreased and is replaced by pioneer trees and Poaceae, when the mineral fluxes attained their lowest values. This episode of maximum dryness is attributed to an abrupt climatic event of global significance which is superimposed onto the paleomonsoon variability. It is related to a cold event, which in turn produced a change in the lower atmospheric circulation that was characterized by a strengthening of northern trade winds, probably correlated with sea-surface temperature variations in the eastern tropical Atlantic area.

Paleoclimatology

10.1006/qres.2001.2240

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Citations (54)

Sedimentary facies and high resolution primary production inferences from laminated diatomacous sediments off northern Chile (23°S)

Marine Geology (2004)

Gabriel Vargas Luc Ortlieb J. Pichon Jacques Bertaux Michel Pujos

Chaetoceros

Biogenic silica

Oxygen minimum zone

Sedimentation

10.1016/j.margeo.2004.05.032

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Citations (54)

Perturbaciones del régimen de las lluvias y condiciones de tipo El Niño en América del Sur tropical desde hace 7000 años

Bulletin de l’Institut français d’études andines (1995)

Louis Martin Jacques Bertaux Marie‐Pierre Ledru Philippe Mourguiart Abdelfettah Sifeddine

Disturbance of rainfall regime and El Niño-like conditions in tropical South America during the last 7000 years Sedimentary records from three geographically and climatically distinct South American areas allowed the reconstruction of the rainfall regime during the last 7 000 yrs. In south-eastern Amazonia, palynological and sedimentological analyses from cores retrieved in lakes of Carajás region (6o S) demonstrated the existence of several periods during which tropical rainforest fires where related to short-term (a few decades) dry periods. Likewise, in central Brazil, palynological and sedimentological analyses from two cores taken in the Salitre area (19o S) and in the Boa Vista region (27o S), revealed strong synchronous though opposite variations in the vegetation. Finally, on the northern Bolivian Altiplano, paleoba thymetric reconstructions performed in Lake Titicaca (14-17o S) also point out to large variations in the precipitation pattern, which can be related to those recorded at Carajás and Salitre. Such variations are similar to those presently related to strong El Niño events.

10.3406/bifea.1995.1209

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Dynamique de l'érosion dans le bassin versant de l'Irrawaddy au cours des deux derniers cycles climatiques (280–0 ka)

Comptes Rendus de l Académie des Sciences - Series IIA - Earth and Planetary Science (2001)

Christophe Colin Jacques Bertaux Laurent Turpin Catherine Kissel

Core MD77-169, located in the Andaman Sea, is characterized by εNd(0) ranging between −9.5 and −11, implying that the Irrawaddy River is the main contributor of detrital material. The pedogenic clays (smectite and kaolinite) to primary mineral (feldspar, quartz, illite and chlorite) ratios show strong precessional cycles, suggesting that they are controlled by past changes in the monsoon intensity. Wet periods of summer monsoon reinforcement are characterized by the increase of chemical weathering and/or physical erosion of the Irrawaddy plain soils. Dans l'océan Indien, au large de la Birmanie (mer d'Andaman), une carotte sédimentaire a été collectée. L'étude des valeurs de εNd(0), comprises entre −9,5 et −11, implique une alimentation détritique du Centre de la mer d'Andaman par le fleuve de l'Irrawaddy. Les variations relatives des minéraux issus d'une pédogenèse poussée (smectite et kaolinite) par rapport aux minéraux primaires (feldspath, quartz, illite et chlorite) présentent un fort signal de précession, suggérant un contrôle par les changements passés de l'intensité de la mousson. Les périodes de fortes précipitations se caractérisent par une augmentation de l'intensité de l'hydrolyse et/ou par une augmentation de l'érosion mécanique des sols de la plaine de l'Irrawaddy.

Illite

10.1016/s1251-8050(01)01565-8

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Paleoclimatic record of speleothems in a tropical region: study of laminated sequences from a Holocene stalagmite in Central–West Brazil

Quaternary International (2002)

Jacques Bertaux Francis Sondag Roberto Ventura Santos François Soubiès Christiane Causse

Stalagmite

Speleothem

10.1016/s1040-6182(01)00077-5

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Citations (56)

Séquences laminées dans une stalagmite holocène du Centre ouest brésilien : étude pétro-stratigraphique préliminaire

Jacques Bertaux Francis Sondag François Soubiès R. V. Santos Paulo César Boggiani

Stalagmite

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Apport de la petrologie structurale a l'etude de filons microgranite intrusifs dans les tufs anthraciferes (Viseen de la region de Roanne, Loire)

BSGF – Earth Sciences Bulletin (1978)

Jacques Bertaux Claude Gagny

Other| January 01, 1978 Apport de la petrologie structurale a l'etude de filons microgranite intrusifs dans les tufs anthraciferes (Viseen de la region de Roanne, Loire) J. Bertaux; J. Bertaux Author Search for other works by this author on: GSW Google Scholar C. Gagny C. Gagny Author Search for other works by this author on: GSW Google Scholar Author and Article Information J. Bertaux Author C. Gagny Author Publisher: Société Géologique de France First Online: 03 Mar 2017 Online ISSN: 1777-5817 Print ISSN: 0037-9409 GeoRef, Copyright 2004, American Geological Institute. Bulletin de la Société Géologique de France (1978) S7-XX (6): 883–887. https://doi.org/10.2113/gssgfbull.S7-XX.6.883 Article history First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J. Bertaux, C. Gagny; Apport de la petrologie structurale a l'etude de filons microgranite intrusifs dans les tufs anthraciferes (Viseen de la region de Roanne, Loire). Bulletin de la Société Géologique de France 1978;; S7-XX (6): 883–887. doi: https://doi.org/10.2113/gssgfbull.S7-XX.6.883 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.

10.2113/gssgfbull.s7-xx.6.883

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Origine métamorphique des grenats des volcanites acides d'âge viséen supérieur dans le nord-est du Massif central français

Bulletin de Minéralogie (1982)

Jacques Bertaux

Garnets of acid volcanics (called « tufs anthracifères ») from the upper Visean, North-East of the French Central Massif, which occur either in metamorphic enclaves or in free xenocrysts, are of metamorphic origin. This result is based upon a comparison of these garnets with those of the neighbouring metamorphic basement of the Forez area. The chemical composition of garnets shows that they first belonged to sillimanite-cordierite bearing rocks. Original metamorphic zoning is preserved in most of the mineral. At the rim, the evolution of the almandine/pyrope ratio in garnets from volcanics is the opposite of that in garnets from the metamorphic basement. This is a consequence of the ultimate magmatic stage of these minerals, during which a plagioclase-biotite reaction rim appears around free garnets. These results suggest the need for reexamining the magmatic origin proposed by several authors for garnets of intermediate and acid volcanics occurring in different areas, these garnets having zoning and chemical characteristics similar to those of the « tufs anthracifères » garnets. Finally, this study of garnets supports the assumption of the origin of acid magmatism from the upper Visean by anatectic melting of continental crust.

Massif

Pyrope

Cordierite

10.3406/bulmi.1982.7607

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Citations (5)

Evolution de la forêt tropicale en Afrique Equatoriale Atlantique durant les 4000 dernières années et héritage sur les paysages végétaux actuels

HAL (Le Centre pour la Communication Scientifique Directe) (1996)

Annie Vincens Aurélie Alexandre Jacques Bertaux R. Dechamps Hilaire Elenga

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Absence of Last Glacial Maximum Records in Lowland Tropical Forests

Quaternary Research (1998)

Marie‐Pierre Ledru Jacques Bertaux Abdelfettah Sifeddine Kenitiro Suguío

Environmental conditions of the lowland tropical forests during the last glacial maximum (LGM) between ca 20,000 and 18,000 14 C yr B.P., are reevaluated in terms of dating control and lithology analyzed in seven pollen records from South America. The reevaluation shows that probably in none of the published records are LGM sediments present or abundant. This conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates. These findings suggest that the LGM was represented probably by a hiatus of several thousand years, indicative of drier climates than before or after.

Last Glacial Maximum

Lithology

10.1006/qres.1997.1953

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Citations (160)