%0 Journal Article
%A Fernández López, Sixto Rafael
%A Gómez Fernández, Juan José
%T The Middle Jurassic eastern margin of the Iberian platform system (eastern Spain). Palaeogeography and biodispersal routes of ammonoids.
%D 2004
%@ 0035-6883
%U https://hdl.handle.net/20.500.14352/50812
%X From a sedimentological and palaeogeographical pointof view, in the eastern margin of the Iberian platform system, MiddleJurassic deposits are represented by a thick pile of carbonates with minormarls interbedded. Different facies, within the Tortosa, Aragoneseand Castilian platforms, pertain to two categories: internal platformand external platform facies. A system of extensional faults was themajor factor determining the differentiation of several shallow, carbonate,epicontinental platforms. The so-called Iberian Basin was ashallow intracratonic platform system, in which a relatively deep extensionalbasin (the Catalan Basin) started to be differentiated duringthe late Bajocian. In the eastern part of this faulted platform system,the occurrence of a listric fault, dipping towards the east, conditionedthe development of a late Bajocian differentiated subsident area namedthe Tortosa Platform.From a palaeobiogeographical point of view, the ammonite fossilassemblages of the Iberian platforms are composed of Sub-Mediterraneantaxa. At the eastern margin of the Iberian platform system,the appearance and distribution of shells of ammonoids were taphonomicallyand ecologically controlled by regional changes of relativesea level. A Sub-Mediterranean zonation can be recognized, althoughmost of the ammonites shells correspond to adult individuals arrivedby necroplanktic drift from more open-marine or oceanic areas. Thefollowing criteria are relevant in recognizing the maximum deepeningepisodes in the Iberian platform system: colonization (including ontogenicdevelopment) of open-marine taxa, immigration of oceanic taxaand development of endemic species. In terms of Sequence Stratigraphy,the development of expanded, external platform sections in the TortosaPlatform during the Garantiana Biochron (late Bajocian) is noteworthy.During this episode, the Iberian platform system reached themaximum bathymetric values and acted as a biogeographical dispersalarea for some taxonomic groups of ammonoids between the WesternTethys and the Proto-Atlantic.
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