@article{NeugebauerBrauerDraegeretal.2012,
  author    = {Neugebauer, Ina and Brauer, Achim and Draeger, Nadine and Dulski, Peter and Wulf, Sabine and Plessen, Birgit and Mingram, Jens and Herzschuh, Ulrike and Brande, Arthur},
  title     = {A Younger Dryas varve chronology from the Rehwiese palaeolake record in NE-Germany},
  series = {Quaternary science reviews : the international multidisciplinary research and review journal},
  volume    = {36},
  journal   = {Quaternary science reviews : the international multidisciplinary research and review journal},
  number    = {10},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0277-3791},
  doi       = {10.1016/j.quascirev.2011.12.010},
  pages     = {91 -- 102},
  year      = {2012},
  abstract  = {The first 1400-year floating varve chronology for north-eastern Germany covering the late Allered to the early Holocene has been established by microscopic varve counts from the Rehwiese palaeolake sediment record. The Laacher See Tephra (LST), at the base of the studied interval, forms the tephrochronological anchor point. The fine laminations were examined using a combination of micro-facies and mu XRF analyses and are typical of calcite varves, which in this case provide mainly a warm season signal. Two varve types with different sub-layer structures have been distinguished: (I) complex varves consisting of up to four seasonal sub-layers formed during the Allered and early Holocene periods, and, (II) simple two sub-layer type varves only occurring during the Younger Dryas. The precision of the chronology has been improved by varve-to-varve comparison of two independently analyzed sediment profiles based on well-defined micro-marker layers. This has enabled both (1) the precise location of single missing varies in one of the sediment profiles, and, (2) the verification of varve interpolation in disturbed varve intervals in the parallel core. Inter-annual and decadal-scale variability in sediment deposition processes were traced by multi-proxy data series including seasonal layer thickness, high-resolution element scans and total organic and inorganic carbon data at a five-varve resolution. These data support the idea of a two-phase Younger Dryas, with the first interval (12,675-12,275 varve years BP) characterised by a still significant but gradually decreasing warm-season calcite precipitation and a second phase (12,275-11,690 varve years BP) with only weak calcite precipitation. Detailed correlation of these two phases with the Meerfelder Maar record based on the LST isochrone and independent varve counts provides clues about regional differences and seasonal aspects of YD climate change along a transect from a location proximal to the North Atlantic in the west to a more continental site in the east},
  language  = {en}
}
@article{HoehnelReimoldAltenbergeretal.2018,
  author    = {Hoehnel, Desir{\´e}e and Reimold, Wolf Uwe and Altenberger, Uwe and Hofmann, Axel and Mohr-Westheide, Tanja and Oezdemir, Seda and K{\"o}berl, Christian},
  title     = {Petrographic and Micro-XRF analysis of multiple archean impact-derived spherule layers in drill core CT3 from the northern Barberton Greenstone Belt (South Africa)},
  series = {Journal of African earth sciences / Geological Society of Africa},
  volume    = {138},
  journal   = {Journal of African earth sciences / Geological Society of Africa},
  publisher = {Elsevier Science},
  address   = {Oxford},
  issn      = {1464-343X},
  doi       = {10.1016/j.jafrearsci.2017.11.020},
  pages     = {264 -- 288},
  year      = {2018},
  abstract  = {The Archean spherule layers (SLs) of the Barberton Greenstone Belt (BGB, South Africa) and Pilbara Craton (Australia) are the only known evidence of early, large impact events on Earth. Spherules in these layers have been, alternatively, interpreted as molten impact ejecta, condensation products from an impact vapor cloud, or ejecta from impact craters melted during atmospheric re-entry. Recently, a new exploration drill core (CT3) from the northern BGB revealed 17 SL intersections. Spherules are densely packed, sand-sized, and variably rounded or deformed. The CT3 SLs are intercalated with black and brown shale, and laminated chert. The determination of the original number of impact events that are represented by these multiple SLs is central to the present paper. A comprehensive study of the sedimentary and petrographic characteristics of these SLs involved the determination of the size, shape and types of individual spherules, as well as their mineralogy. CT3 SLs consist of K-feldspar, phyllosilicate, siderite, dolomite, quartz, Ti- and Fe-oxides, as well as apatite. In addition, small amounts of carbonaceous, presumably organic material are observed in several spherules at 145 and 149 m depth. Only Ni-rich Cr-spinel (up to 11 wt\% NiO) crystals, rare zircon grains, and alloys of platinum group elements ± Fe or Ni represent primary phases in these thoroughly altered strata. The 0.3 to 2.6-mm-sized spherules can be classified into four types: 1. Spherules crystallized completely with secondary K-feldspar (subtype 1A) or phyllosilicate (subtype 1B); spherules completely filled with Ti- and Fe-oxides (subtype 1C); spherules containing disordered or radially oriented, fibrous and lath-shaped K-feldspar textures (subtype 1D); or subtype 1B spherules that contain significant Cr-spinel (subtype 1E); 2. zoned compositions with these types 1A and/or 1B minerals (subtype 2A); spherules that contain central or marginal vesicles (subtype 2B); subtype 1B spherules whose rims consist of Ti and Fe-oxides (subtype 2C); 3. deformed spherules (subtype 3A) - of all types; (B) subtype 1B spherules are assimilated into groundmass; (C) open spherules or spherules with collapsed rims; and 4. interconnected spherules of type 1A. A few spherules show botryoidal devitrification textures interpreted to result from rapid cooling/devitrification of former melt droplets. SL 15 at a depth of 145 m is unique in being the only grain-size sorted SL; this bed may have been deposited by fallout through a water column. The SL and their host rocks can be easily distinguished by their significant differences in micro-XRF elemental distribution maps. Depending on which aspects of the SLs are primarily considered (such as similar geochemistry, similar layering, SL occurrences abundant at three different depth intervals), the 17 CT3 SLs can be assigned to three or up to 13 individual impact events. Uncertainty about the actual number of impact events represented remains, however, due to the complex folding deformation observed throughout the drill core.},
  language  = {en}
}