An improved model for the ikaite-glendonite transformation: evidence from the Lower Cretaceous of Spitsbergen, Svalbard

Abstract

Glendonites, pseudomorphs after marine sedimentary ikaite, are found throughout the Lower Cretaceous succession of Svalbard. Existing models for the ikaite-to-glendonite transformation do not explain the different petrological fabrics observed in the glendonites of Lower Cretaceous Svalbard. This study presents an improved model for the formation of these glendonites, based on petrographic and geochemical observations, and published work on ikaite breakdown. We show that for the glendonites of Lower Cretaceous Svalbard, methane is unlikely to be the sole or indeed main driver behind their formation, and present an improved model for their formation that accounts for the varied petrographic fabrics observed in these particular glendonites. Coupled with our new model, stable isotope data demonstrate why bulk samples of ancient glendonite cannot be used for palaeotemperature reconstructions.

Glendonite-Like Carbonate Aggregates from the Lower Ordovician Koporye Formation (Russian Part of the Baltic Klint): Detailed Mineralogical and Geochemical Data and Paleogeographic Implications

“…Isotopic data from the studied anthraconite samples fall within a narrow range and show values which are comparable to those observed in Mesozoic and Paleozoic glendonites (for details see [34] and references therein). Monominerallic (calcite) and polyminerallic anthraconite samples do not show substantial difference in isotopic ratios.…”

“…Three carbonate phases were found within the studied anthraconites. The first phase of calcite is dull red to dark-red and contains concentric zonation in CL, which represent comparable characteristics to calcite often interpreted as being derived from ikaite replacement in glendonite concretions [31,32,34,38]. The source of the first calcite phase is therefore likely to be primary ikaite.…”

“…Our data on the morphology, internal structure, mineralogy, and isotopic composition of Lower Ordovician anthraconites of the Baltic paleobasin reveal many similarities to glendonites. Glendonites are usually found in terrigenous sediments, ranging from mudstones to sandstones ( [31][32][33][34], amongst others), while modern ikaite crystals are known from muddy deposits [35] and organic-rich sediments [36,37].…”

Ichnofossils, Cracks or Crystals? A Test for Biogenicity of Stick-Like Structures from Vera Rubin Ridge, Mars

“…Tectographs, i.e., pseudofossils produced by the movement of rock layers relative to each other [34], can be rejected as an explanation for the Vera Rubin Ridge structures because the stick-like features are not parallel between each other. [37] showing sharp contact with the host rock (Sh). Early Cretaceous of Svalbard.…”

Marine reptiles and climates of the Jurassic and Cretaceous of Siberia

“…Несмотря на то, что часть факторов, контролирующих распространение глендонитов, остается предметом дискуссий (Zhou et al, 2015;morales et al, 2017;Qu et al, СТРАТИгРАфИя. гЕОлОгИчЕСКАя КОРРЕляцИя том 27 № 4 2019 2017; stockmann et al, 2018), общепризнаны их приуроченность к холодноводным обстановкам и то, что исходным минералом для образования глендонитов является икаит (Grasby et al, 2017;rogov et al, 2017;vickers et al, 2018). В дополнение к полученным в последнее время новым данным по палеоклиматам, М.А.…”