Similarities and differences in the dolomitization history of two coeval Middle Triassic carbonate platforms, Balaton Highland, Hungary

Dolomitization of platform carbonates is commonly the result of multiphase processes. Documentation of the complex dolomitization history is difficult if completely dolomitized sections are studied. Two Middle Anisian sections representing two coeval carbonate platforms were investigated and compared in the present study. Both sections are made up of meter-scale peritidal–lagoonal cycles with significant pedogenic overprint. One of the sections contains non-dolomitized, partially dolomitized, and completely dolomitized intervals, whereas the other is completely dolomitized. Based on investigations of the partially dolomitized section, penecontemporaneous dolomite formation and/or very early post-depositional dolomitization were identified in various lithofacies types. In shallow subtidal facies, porphyrotopic dolomite was found preferentially in microbial micritic fabrics. Microbially induced dolomite precipitation and/or progressive replacement of carbonate sediments could be interpreted for stromatolites. Cryptocrystalline to very finely crystalline dolomite, probably of pedogenic origin, was encountered in paleosoil horizons. Fabric-destructive dolomite commonly found below these horizons was likely formed via reflux of evaporated seawater. As a result of the different paleogeographic settings of the two platforms, their shallow-burial conditions were significantly different. One of the studied sections was located at the basinward platform margin where pervasive fabric-retentive dolomitization took place in a shallow-burial setting, probably via thermal convection. In contrast, in the area of the other, smaller platform shallow-water carbonates were covered by basinal deposits, preventing fluid circulation and accordingly pervasive shallow-burial dolomitization. In the intermediate to deep burial zone, recrystallization of partially dolomitized limestone and occlusion of newly opened fractures and pores by coarsely crystalline dolomite took place

Unusually thick dinosaur eggshell fragments from the Spanish Late Cretaceous

[EN] Fieldwork carried out recently in the southeastern branch of the Iberian Range (Valencia Province, Spain) has led to the collection of a large volume of dinosaur eggshell fragments of unusual thickness. These specimens, up to 4.9 mm thick, were recovered from palustrine grey marls of the upper Campanian-lower Maastrichtian Sierra Perenchiza Formation, which comprises a wetland paleoenvironment deposit. These eggshell fragments have a characteristic compactituberculate ornamentation, dinosauroid-spherulitic organisation, and exhibit a complex canaliculate respiratory system. The external tuberculate surface of the shell as well as the internal microstructure enable referral to Megaloolithus aff. siruguei, the most common megaloolithid oospecies known from the Iberian Peninsula and southern France. The biostratigraphic range of M. siruguei matches the temporal distribution of titanosaurid dinosaurs across the Iberian Range, tentatively considered to be potential producers.This work was supported by the Ministerio de Economia y Competitividad of Spain [Secretaria de Estado de Investigacion, Desarrollo e Innovacion, projects CGL2013-47521-P and CGL2014-53548-P]Company Rodríguez, J. (2017). Unusually thick dinosaur eggshell fragments from the Spanish Late Cretaceous. Historical Biology (Online). 31(2):203-210. https://doi.org/10.1080/08912963.2017.1357717S203210312Allain, R., & Suberbiola, X. P. (2003). Dinosaurs of France. Comptes Rendus Palevol, 2(1), 27-44. doi:10.1016/s1631-0683(03)00002-2Bravo, A. M., & Gaete, R. (2014). Titanosaur eggshells from the Tremp Formation (Upper Cretaceous, Southern Pyrenees, Spain). Historical Biology, 27(8), 1079-1089. doi:10.1080/08912963.2014.934231Canudo, J. I., Oms, O., Vila, B., Galobart, À., Fondevilla, V., Puértolas-Pascual, E., … Blanco, A. (2016). The upper Maastrichtian dinosaur fossil record from the southern Pyrenees and its contribution to the topic of the Cretaceous–Palaeogene mass extinction event. Cretaceous Research, 57, 540-551. doi:10.1016/j.cretres.2015.06.013Cruzado-Caballero, P., Ruiz-Omeñaca, J. I., Gaete, R., Riera, V., Oms, O., & Canudo, J. I. (2013). A new hadrosaurid dentary from the latest Maastrichtian of the Pyrenees (north Spain) and the high diversity of the duck-billed dinosaurs of the Ibero-Armorican Realm at the very end of the Cretaceous. Historical Biology, 26(5), 619-630. doi:10.1080/08912963.2013.822867Chiappe, L. M., Coria, R. A., Dingus, L., Jackson, F., Chinsamy, A., & Fox, M. (1998). Sauropod dinosaur embryos from the Late Cretaceous of Patagonia. Nature, 396(6708), 258-261. doi:10.1038/24370Company J. 2004. Vertebrados continentales del Cretácico superior (Campaniense-Maastrichtiense) de Valencia [PhD dissertation]. Valencia: Universidad de Valencia.Company, J., & Szentesi, Z. (2012). Amphibians from the Late Cretaceous Sierra Perenchiza Formation of the Chera Basin, Valencia Province, Spain. Cretaceous Research, 37, 240-245. doi:10.1016/j.cretres.2012.04.003Csiki-Sava, Z., Buffetaut, E., Ősi, A., Pereda-Suberbiola, X., & Brusatte, S. L. (2015). Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. ZooKeys, 469, 1-161. doi:10.3897/zookeys.469.8439Erben, H. K., Hoefs, J., & Wedepohl, K. H. (1979). Paleobiological and isotopic studies of eggshells from a declining dinosaur species. Paleobiology, 5(4), 380-414. doi:10.1017/s0094837300016900García, R. A. (2007). An «egg-tooth»–like structure in titanosaurian sauropod embryos. Journal of Vertebrate Paleontology, 27(1), 247-252. doi:10.1671/0272-4634(2007)27[247:aesits]2.0.co;2Garcia, G., & Vianey-Liaud, M. (2001). Dinosaur eggshells as biochronological markers in Upper Cretaceous continental deposits. Palaeogeography, Palaeoclimatology, Palaeoecology, 169(1-2), 153-164. doi:10.1016/s0031-0182(01)00215-2Grellet-Tinner, G., Chiappe, L. M., & Coria, R. (2004). Eggs of titanosaurid sauropods from the Upper Cretaceous of Auca Mahuevo (Argentina). Canadian Journal of Earth Sciences, 41(8), 949-960. doi:10.1139/e04-049Grigorescu, D., Garcia, G., Csiki, Z., Codrea, V., & Bojar, A.-V. (2010). Uppermost Cretaceous megaloolithid eggs from the Haţeg Basin, Romania, associated with hadrosaur hatchlings: Search for explanation. Palaeogeography, Palaeoclimatology, Palaeoecology, 293(3-4), 360-374. doi:10.1016/j.palaeo.2010.03.031Izquierdo LA, Montero D, Pérez G, Urién V, Meijide M. 2001. Macroestructura de huevos de dinosaurios en el Cretácico superior de “La Rosaca” (Burgos, España). Actas de las I Jornadas Internacionales Sobre Paleontología de Dinosaurios y su Entorno. Ed. Colectivo Arqueológico y Paleontológico de Salas. Salas de los Infantes. p. 389–395.Jackson FD. 2007. Titanosaur reproductive biology: comparison of the Auca Mahuevo Titanosaur nesting locality (Argentina), to the Pinyes Megaloolithus nesting locality (Spain) [PhD dissertation]. Bozeman (MT): Montana State University.Jackson, F. D., Garrido, A., Schmitt, J. G., Chiappe, L. M., Dingus, L., & Loope, D. B. (2004). Abnormal, multilayered titanosaur (Dinosauria: Sauropoda) eggs from in situ clutches at the Auca Mahuevo locality, Neuquen Province, Argentina. Journal of Vertebrate Paleontology, 24(4), 913-922. doi:10.1671/0272-4634(2004)024[0913:amtdse]2.0.co;2Jackson, F. D., Varricchio, D. J., Jackson, R. A., Vila, B., & Chiappe, L. M. (2008). 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Combined Use of Electron and Light Microscopy Techniques Reveals False Secondary Shell Units in Megaloolithidae Eggshells. PLOS ONE, 11(5), e0153026. doi:10.1371/journal.pone.0153026Moreno-Azanza, M., Bauluz, B., Canudo, J. I., Puértolas-Pascual, E., & Sellés, A. G. (2013). A re-evaluation of aff. Megaloolithidae eggshell fragments from the uppermost Cretaceous of the Pyrenees and implications for crocodylomorph eggshell structure. Historical Biology, 26(2), 195-205. doi:10.1080/08912963.2013.786067Oms, O., Dinarès-Turell, J., Vicens, E., Estrada, R., Vila, B., Galobart, À., & Bravo, A. M. (2007). Integrated stratigraphy from the Vallcebre Basin (southeastern Pyrenees, Spain): New insights on the continental Cretaceous−Tertiary transition in southwest Europe. Palaeogeography, Palaeoclimatology, Palaeoecology, 255(1-2), 35-47. doi:10.1016/j.palaeo.2007.02.039Ortega, F., Bardet, N., Barroso-Barcenilla, F., Callapez, P. M., Cambra-Moo, O., Daviero- Gómez, V., … Sanz, J. L. (2015). 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Características petrográficas y datación U/Th de una calcreta laminar Cuaternaria: Implicaciones de la captura de la Cuenca de Guadix-Baza por el río Guadalquivir.

The Guadix topographic depression is a Neogene-Quaternary basin located in the central sector of the Betic Cordillera at the boundary between the South Iberian margin and the Alboran domain. This topographic depression is a plateau with an average elevation of 1000 m in the northern limb of the Sierra Nevada range. The continental deposits infilling the Guadix basin span time from the late Tortonian to the Pleistocene, when a laminar calcrete developed on fine to coarse-grained fluvial and lacustrine deposits. Four coeval subsamples from the top laminae of the calcrete were collected and dated by the U/Th method. The resulting date is 42.6 ± 5.6 ka, which indicates the minimum age for the cessation of active sedimentation in the Guadix basin. We envisage the capture of the Pliocene-Pleistocene endorheic Guadix basin by the Guadalquivir River after 42 ka as the main factor triggering the formation of the present-day eroded landscape. After the capture, the combination of climatic (wet periods), lithological (soft and loose sediments), and topographic (high average altitude) features allowed the development of the present-day entrenched drainage pattern

Análisis de la erosión diferencial en el pleistoceno superior para las subcuencas de Guadix y Baza.

Erosion rates in the Guadix-Baza basin have been calculated drawing on a volumetric estimation of sediment loss by river erosion since the late Pleistocene. On this purpose we have performed a reconstruction of the glacis surface dated in 42.6 ka and defined by a calcrete layer that capes the basin infilling. In order to support this age, we presented new 14C radiometric data of three travertine platforms formed later to the beginning of the river entrenchment in the basin and a U/Th dating of a lower calcrete situated some meters below the glacis surface. By comparing the reconstructed geomorphic surface and the present day topography we have calculated the volume of sediment lost by hidric erosion in the entire basin. The resulting erosion rates are between 4.28 and 6.57 m3ha-1yr-1. Individual erosion rates for Guadix and Baza sub-basins (11.80 m3ha-1yr-1 and 1.77 m3ha-1yr-1 respectively) suggest different stages of drainage pattern evolution in both sub-basins. We attribute part of the lower values obtained in the Baza sub-basin as related to the down-throwing due to very recent activity along the Baza fault