Walliser, Otto Heinrich

[["dc.bibliographiccitation.firstpage","281"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Facies"],["dc.bibliographiccitation.lastpage","296"],["dc.bibliographiccitation.volume","40"],["dc.contributor.author","Peckmann, Jörn"],["dc.contributor.author","Walliser, Otto Heinrich"],["dc.contributor.author","Riegel, Walter"],["dc.contributor.author","Reitner, Joachim"],["dc.date.accessioned","2019-07-19T10:12:22Z"],["dc.date.available","2019-07-19T10:12:22Z"],["dc.date.issued","1999"],["dc.description.abstract","The Middle Devonian Hollard Mud Mound is situated in the eastern Hamar Laghdad, which is a small mountain range in the Tafilalt in SE Morocco. In contrast to the well known Lower Devonian Kess-Kess mounds, the Hollard Mound is of Middle Devonian age. The facies in the core of this mud mound differs from that of the other parts of the mound, and exhibits signatures of ancient hydrocarbon venting. The carbonate phases of the core facies are derived from the oxidation of vent fluids and consist of clotted micrite, a cryptocrystalline carbonate associated with spheres of uncertain origin, and a calcitic rim cement (rim cement B). These vent carbonates show δ13C values in the range of −11 to −20% PDB indicating that some of their carbon is derived from isotopically light hydrocarbons. Fossiliferous micrite has been affected by hydrocarbon venting in the proximity of the vent site, which is indicated by intermediate δ13C values between vent carbonates and not affected sediments. Bivalves occur in dense populations within the core facies. They form autochthonous shell accumulations and are almost exclusively articulated. it is likely that these bivalves were dependent on chemosynthesis similar to their counterparts at modern vents. The vent deposits also exhibit an unusual prasinophyte assemblage, which might have been linked to the specific nutrient availability at the vent site. The ancient vent site is characterized by an enhanced carbonate precipitation and rapid lithification. The latter is corroborated by the three-dimensional preservation of phytoplankton (prasinophytes and acritarchs) and the occurrence of stromatactoid pores. An early phase of carbonate corrosion predating the formation of vent carbonates affected the fossiliferous micrite of the core facies and is thought to be related to a phase of H2S-rich venting."],["dc.identifier.doi","10.1007/BF02537477"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/61776"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.issn","0172-9179"],["dc.relation.issn","1612-4820"],["dc.title","Signatures of hydrocarbon venting in a Middle Devonian Carbonate Mound (Hollard Mound) at the Hamar Laghdad (Antiatlas, Morocco)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","114"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Palaios"],["dc.bibliographiccitation.lastpage","122"],["dc.bibliographiccitation.volume","22"],["dc.contributor.author","Peckmann, Joern"],["dc.contributor.author","Campbell, Kathleen A."],["dc.contributor.author","Walliser, Otto H."],["dc.contributor.author","Reitner, Joachim"],["dc.date.accessioned","2018-07-05T07:47:39Z"],["dc.date.available","2018-07-05T07:47:39Z"],["dc.date.issued","2007"],["dc.description.abstract","A spectacular carbonate deposit from the western Meseta of Morocco consists of microbial and brachiopod limestones. The small, metersized Famennian limestone blocks are embedded in Carboniferous shales, implying later displacement. Primary deposition of the limestones apparently occurred below the depth limit of phototrophic organisms. The brachiopods belong to the genus Dzieduszyckia within the rhynchonellide superfamily Dimerelloidea. They occur in fantastic abundance, in a low-diversity faunal assemblage. The microbial limestones contain fossilized threadlike microorganisms of unknown affiliation. The enormous accumulation of brachiopods on the Famennian seafloor is best explained by the former existence of a seep. Crude oil was a major component of the seepage fluids, as indicated by the occurrence of pyrobitumen (metamorphosed petroleum) and delta C-13(carbonate) values as low as -12 parts per thousand, akin to the isotopic composition of carbonates forming at modern oil seeps. The lowest delta C-13 values in the Dzieduszyckia deposit are found for a carbonate phase referred to as banded/botryoidal cement. It is a fibrous, low-Mg calcite cement in the form of isopachous rims and botryoids that precipitated directly on and within brachiopod shells. The microbial limestones predominantly consist of this phase and therefore can be classified as cement framestones. Reticulate patterns of botryoidal aggregates and an elevated Sr content agree with an aragonite precursor of the banded/botryoidal cement. The interpretation of the Dzieduszyckia deposit as seep related supports the hypothesis that Paleozoic and Mesozoic members of the rhynchonellide superfamily Dimerelloidea were a lineage long associated with seeps that survived from Late Devonian to Early Cretaceous time."],["dc.identifier.doi","10.2110/palo.2005.p05-115r"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15166"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation.eissn","0883-1351"],["dc.title","A Late Devonian Hydrocarbon-Seep Deposit Dominated By Dimerelloid Brachiopods, Morocco"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]