@article{ChristMaerzKutscheraetal.2017,
  author    = {Christ, Nicolas and Maerz, Sven and Kutschera, Edgar and Kwiecien, Ola and Mutti, Maria},
  title     = {Palaeoenvironmental and diagenetic reconstruction of a closed-lacustrine carbonate system},
  series = {Sedimentology : the journal of the International Association of Sedimentologists},
  volume    = {65},
  journal   = {Sedimentology : the journal of the International Association of Sedimentologists},
  number    = {1},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0037-0746},
  doi       = {10.1111/sed.12401},
  pages     = {235 -- 262},
  year      = {2017},
  abstract  = {Chemostratigraphic studies on lacustrine sedimentary sequences provide essential insights on past cyclic climatic events, on their repetition and prediction through time. Diagenetic overprint of primary features often hinders the use of such studies for palaeoenvironmental reconstruction. Here the potential of integrated geochemical and petrographic methods is evaluated to record freshwater to saline oscillations within the ancient marginal lacustrine carbonates of the Miocene Ries Crater Lake (Germany). This area is critical because it represents the transition from shoreline to proximal domains of a hydrologically closed system, affected by recurrent emergent events, representing the boundaries of successive sedimentary cycles. Chemostratigraphy targets shifts related to subaerial exposure and/or climatic fluctuations. Methods combine facies changes with C-13-O-18 chemostratigraphy from matrix carbonates across five closely spaced, temporally equivalent stratigraphic sections. Isotope composition of ostracod shells, gastropods and cements is provided for comparison. Cathodoluminescence and back-scatter electron microscopy were performed to discriminate primary (syn-)depositional, from secondary diagenetic features. Meteoric diagenesis is expressed by substantial early dissolution and dark blue luminescent sparry cements carrying negative C-13 and O-18. Sedimentary cycles are not correlated by isotope chemostratigraphy. Both matrix C-13 and O-18 range from ca -75 to +40 parts per thousand and show clear positive covariance (R=097) whose nature differs from that of previous basin-oriented studies on the lake: negative values are here unconnected to original freshwater lacustrine conditions but reflect extensive meteoric diagenesis, while positive values probably represent primary saline lake water chemistry. Noisy geochemical curves relate to heterogeneities in (primary) porosity, resulting in selective carbonate diagenesis. This study exemplifies that ancient lacustrine carbonates, despite extensive meteoric weathering, are able to retain key information for both palaeoenvironmental reconstruction and the understanding of diagenetic processes in relation to those primary conditions. Also, it emphasizes the limitation of chemostratigraphy in fossil carbonates, and specifically in settings that are sensitive for the preservation of primary environmental signals, such as lake margins prone to meteoric diagenesis.},
  language  = {en}
}
@article{FoellmiHofmannChiaradiaetal.2015,
  author    = {F{\"o}llmi, Karl B. and Hofmann, Helene and Chiaradia, Massimo and de Kaenel, Eric and Frijia, Gianluca and Parente, Mariano},
  title     = {Miocene phosphate-rich sediments in Salento (southern Italy)},
  series = {Sedimentary geology : international journal of applied and regional sedimentology},
  volume    = {327},
  journal   = {Sedimentary geology : international journal of applied and regional sedimentology},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0037-0738},
  doi       = {10.1016/j.sedgeo.2015.07.009},
  pages     = {55 -- 71},
  year      = {2015},
  abstract  = {The upper Middle to lower Upper Miocene (Serravallian to Tortonian) sedimentary succession in Salento (southern Italy) includes glauconite- and phosphate-rich deposits, which are associated with pelagic micrite. In Baia del Ciolo and Marittima (southern Salento), the succession is composed of shallow-water platform carbonates of Late Oligocene age (Chattian; Porto Badisco Formation), which are overlain by a 20- to 30-cm-thick level of glauconite-rich micrite with abundant reworked particles and fossils of the underlying Porto Badisco Formation. This interval is in turn covered by an up to 15 cm thick phosphatic crust ("Livello ad Aturia"), which itself is overlain either by a hemipelagic chalk-like carbonate of Middle to Late Miocene age ("Pietra Leccese"; Marittima) or directly by a micrite of Late Miocene age (Messinian; Novaglie Formation; Baia del Ciolo), which shallows upwards into a shallow-water platform carbonate. A large hiatus is present in this succession, which likely includes the Lower and lower Middle Miocene. In the region of Lecce, two discrete levels enriched in glauconite and phosphate-each associated with a major discontinuity-occur within the Pietra Leccese. The strontium-isotope ages derived on phosphate nodules and phosphatized and non-phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13.5 and 7.5 Ma, with two clusters at 12 and 10.5 Ma. The glauconite and phosphate-rich sediments resulted from a current-dominated regime, which was characterized by low overall sedimentation rates, erosion and sediment reworking, and authigenesis. This regime was likely related to a generally westward-directed bottom current, which was forced to upwell once it arrived at the western border of the eastern Mediterranean basin. The timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the Mediterranean (Malta, Gozo, southern Sicily, Matese, Latium-Abruzzi platform). The partial diachrony in phosphogenesis may express the effect of lateral switching in and/or focusing of upwelling zones. (C) 2015 Elsevier B.V. All rights reserved.},
  language  = {en}
}