Metriorhynchidae) du Valanginien de Barret-le-Bas (Hautes Alpes, France): un cas unique de remont... more Metriorhynchidae) du Valanginien de Barret-le-Bas (Hautes Alpes, France): un cas unique de remont6e des narines externes parmi les crocodiliens. [Enaliosuchus macrospondylus KOKEN, 1883 (Crocodylia Metriorhynchidae) from the Valanginian of Barret-le-Bas (Hautes Alpes, France): a unique case of high hare raising among crocodilians]. GEO-BIOS, 33, 4:: 467-474. Villeurbanne, le 31.04.2000. Manuscrit d6pos6 le 04.11.1999; accept6 d6finitivement le 25.01.2000. R]~SUM]~ -Un squelette axial sub-complet d'Enaliosuchus macrospondylus KOKEN, 1883 (Crocodylia, Metriorhynchidae) a 6t6 d6couvert dans le Valanginien inf6rieur (zone ~ Campylotoxus) de la r6gion de Barret-le-Bas (Hautes Alpes). Ce squelette est le plus complet et le mieux cal6 stratigraphiquement appartenant ~ ce genre. Seuls deux autres sp6cimens plus fragmentaires sont connus. Cet animal repr6sente l'un des tout derniers Metriorhynchidae connus. I1 pr6sente un cas unique de remont6e des narines externes chez un crocodilien, caract~re inconnu jusque 1~ dans ce taxon. MOTS-CL]~S: ENALIOSUCHUS, METRIORHYNCHIDAE, VALANGINIEN, HAUTES ALPES.
ABSTRACT Significantly higher extinction compared to the normal background extinction is noted am... more ABSTRACT Significantly higher extinction compared to the normal background extinction is noted among Tethyan belemnites in the ‘Horizon à Neocomiensis’ (the upper part of the Verrucosum Subzone). Several genera and species of belemnites disappear at the base of this deposit. Certain morphological forms are no longer found, i.e., species with conical rostra and relatively deep alveolae. According to our stratigraphical data this extinction event is linked to sequence boundary Va 4 (type-1 sequence). Of general interest is the appearance of the Boreal belemnite Hibolithes cf.jaculoides Swinnerton, 1936 after the extinction event. One new genus, Mirabelobelus, and two new species, M. blainvillei and M. orbignyi, are described based on ‘Belemnites bicanaliculatus’ de Blainville, 1827.
Stable carbon, oxygen and strontium isotope records were obtained from latest Hauterivian to earl... more Stable carbon, oxygen and strontium isotope records were obtained from latest Hauterivian to earliest Aptian belemnite rostra, which were collected in well-dated sections from the Vocontian Trough (SE France). This data set complements previously published belemnite-isotope records from the latest Berriasian-Hauterivian interval from the same basin. The belemnite carbon and oxygen isotope record is compared to the carbonate bulk-rock isotope record from the same sections, and from additional Italian sections. With regards to their long-term trends, both belemnite and whole-rock δ¹ 8 O records are well correlated except for the latest Hauterivian-Early Barremian period, during which they deviate. This discrepancy is interpreted to be linked to the latest Hauterivian Faraoni oceanic anoxic event and its Early Barremian aftermath. The Faraoni level is characterized by enhanced sea-water stratification, probably induced by the onset of a warmer and more humid climate along the northern Tethyan margin. The Early Barremian is characterized by stronger vertical seawater mixing reflected by a decrease in density contrast between sea-surface and deeper waters. The belemnite oxygen isotope record shows a more stable evolution with smaller fluctuations than its bulk-rock counterpart, which indicates that deeper water masses were not as much subjected to density fluctuations as sea-surface water. The comparison of belemnite and bulk-rock carbon isotope records allows observing the impact of regional influence exerted by platform carbonate ooze shedding on the carbon cycle. Discrepancies in the two records are observed during time of photozoan carbonate platform growth. The strontium isotopic record shows a gradual increase from the latest Berriasian to the latest Early Barremian followed by a rapid decrease until the latest Barremian and a renewed small increase during the earliest Aptian. The major inflection point in the latest Early Barremian appears to predate the onset in the formation of the Ontong-Java volcanic plateau.
Metriorhynchidae) du Valanginien de Barret-le-Bas (Hautes Alpes, France): un cas unique de remont... more Metriorhynchidae) du Valanginien de Barret-le-Bas (Hautes Alpes, France): un cas unique de remont6e des narines externes parmi les crocodiliens. [Enaliosuchus macrospondylus KOKEN, 1883 (Crocodylia Metriorhynchidae) from the Valanginian of Barret-le-Bas (Hautes Alpes, France): a unique case of high hare raising among crocodilians]. GEO-BIOS, 33, 4:: 467-474. Villeurbanne, le 31.04.2000. Manuscrit d6pos6 le 04.11.1999; accept6 d6finitivement le 25.01.2000. R]~SUM]~ -Un squelette axial sub-complet d'Enaliosuchus macrospondylus KOKEN, 1883 (Crocodylia, Metriorhynchidae) a 6t6 d6couvert dans le Valanginien inf6rieur (zone ~ Campylotoxus) de la r6gion de Barret-le-Bas (Hautes Alpes). Ce squelette est le plus complet et le mieux cal6 stratigraphiquement appartenant ~ ce genre. Seuls deux autres sp6cimens plus fragmentaires sont connus. Cet animal repr6sente l'un des tout derniers Metriorhynchidae connus. I1 pr6sente un cas unique de remont6e des narines externes chez un crocodilien, caract~re inconnu jusque 1~ dans ce taxon. MOTS-CL]~S: ENALIOSUCHUS, METRIORHYNCHIDAE, VALANGINIEN, HAUTES ALPES.
ABSTRACT Significantly higher extinction compared to the normal background extinction is noted am... more ABSTRACT Significantly higher extinction compared to the normal background extinction is noted among Tethyan belemnites in the ‘Horizon à Neocomiensis’ (the upper part of the Verrucosum Subzone). Several genera and species of belemnites disappear at the base of this deposit. Certain morphological forms are no longer found, i.e., species with conical rostra and relatively deep alveolae. According to our stratigraphical data this extinction event is linked to sequence boundary Va 4 (type-1 sequence). Of general interest is the appearance of the Boreal belemnite Hibolithes cf.jaculoides Swinnerton, 1936 after the extinction event. One new genus, Mirabelobelus, and two new species, M. blainvillei and M. orbignyi, are described based on ‘Belemnites bicanaliculatus’ de Blainville, 1827.
Stable carbon, oxygen and strontium isotope records were obtained from latest Hauterivian to earl... more Stable carbon, oxygen and strontium isotope records were obtained from latest Hauterivian to earliest Aptian belemnite rostra, which were collected in well-dated sections from the Vocontian Trough (SE France). This data set complements previously published belemnite-isotope records from the latest Berriasian-Hauterivian interval from the same basin. The belemnite carbon and oxygen isotope record is compared to the carbonate bulk-rock isotope record from the same sections, and from additional Italian sections. With regards to their long-term trends, both belemnite and whole-rock δ¹ 8 O records are well correlated except for the latest Hauterivian-Early Barremian period, during which they deviate. This discrepancy is interpreted to be linked to the latest Hauterivian Faraoni oceanic anoxic event and its Early Barremian aftermath. The Faraoni level is characterized by enhanced sea-water stratification, probably induced by the onset of a warmer and more humid climate along the northern Tethyan margin. The Early Barremian is characterized by stronger vertical seawater mixing reflected by a decrease in density contrast between sea-surface and deeper waters. The belemnite oxygen isotope record shows a more stable evolution with smaller fluctuations than its bulk-rock counterpart, which indicates that deeper water masses were not as much subjected to density fluctuations as sea-surface water. The comparison of belemnite and bulk-rock carbon isotope records allows observing the impact of regional influence exerted by platform carbonate ooze shedding on the carbon cycle. Discrepancies in the two records are observed during time of photozoan carbonate platform growth. The strontium isotopic record shows a gradual increase from the latest Berriasian to the latest Early Barremian followed by a rapid decrease until the latest Barremian and a renewed small increase during the earliest Aptian. The major inflection point in the latest Early Barremian appears to predate the onset in the formation of the Ontong-Java volcanic plateau.
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