A reappraisal of the Carboniferous macrofloras of the Zonguldak - Amasra Coal Basin, north-western Turkey
The Zonguldak – Amasra Coal Basin in north-western Turkey has Carboniferous terrestrial deposits ranging in age from Arnsbergian to late Asturian or possibly early Cantabrian. They yield macrofloras that allow detailed biostratigraphical correlations with sequences in Europe. These correlations suggest there are substantial gaps in the Zonguldak – Amasra succession, with middle to upper Namurian, upper Langsettian, Duckmantian and lower Asturian strata apparently being missing. This in turn suggests the area was subjected to significant tectonic instability during Pennsylvanian (late Carboniferous) times and that this might have been instrumental in initiating the progressive change in composition and eventual collapse of the coal swamp biome across Variscan Euramerica during Westphalian times.
High‐precision U‐Pb zircon age calibration of the global Carboniferous time scale and Milankovitch band cyclicity in the Donets Basin, eastern Ukraine
High‐precision ID‐TIMS U‐Pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic, cyclostratigraphic, and biostratigraphic framework of the Carboniferous Donets Basin of eastern Europe. Chemical abrasion of zircons, use of the internationally calibrated EARTHTIME mixed U‐Pb isotope dilution tracer, and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of <0.05%, or ∼100 ka, for these Carboniferous volcanics. This precision allows the resolution of time in the Milankovitch band and confirms the long‐standing hypothesis that individual high‐frequency Pennsylvanian cyclothems and bundles of cyclothems into fourth‐order sequences are the eustatic response to orbital eccentricity (∼100 and 400 ka) forcing. Tuning of the fourth‐order sequences in the Donets Basin to the long‐period eccentricity cycle results in a continuous age model for the Middle to Late Pennsylvanian (Moscovian‐Kasimovian‐Ghzelian) strata of the basin and their record of biological and climatic changes through the latter portion of the late Paleozoic Ice Age. Detailed fusulinid and conodont zonations allow the export of this age model to sections throughout Euramerica. Additional ages for Mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.