Exceptional fossil preservation during CO2 greenhouse crises?

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t a r t i c l e i n f o Exceptional fossil preservation may require not only exceptional places, but exceptional times, as demonstrated here by two distinct types of analysis. First, irregular stratigraphic spacing of horizons yielding articulated Triassic fishes and Cambrian trilobites is highly correlated in sequences in different parts of the world, as if there were short temporal intervals of exceptional preservation globally. Second, compilations of ages of well-dated fossil localities show spikes of abundance which coincide with stage boundaries, mass extinctions, oceanic anoxic events, carbon isotope anomalies, spikes of high atmospheric carbon dioxide, and transient warm-wet paleoclimates. Exceptional fossil preservation may have been promoted during unusual times, comparable with the present: CO 2 greenhouse crises of expanding marine dead zones, oceanic acidification, coral bleaching, wetland eutrophication, sea level rise, ice-cap melting, and biotic invasions. Commercial fossil collectors continue to produce beautifully prepared , fully articulated, complex fossils of scientific (Simmons et al., 2008), as well as market value (Forster, 2001). Such highly prized fossils of vertebrates, trilobites, crinoids and starfish are not unusual because commercially viable horizons yield them at a predictable low rate of return. Such predictably productive horizons are targeted for expensive and time consuming quarrying and preparation by academic paleon-tologists as well (Furrer, 1995). Commercially and scientifically valuable fossil localities are local feasts amid a general famine of poorly preserved fossils, and large volumes of unfossiliferous rock. A variety of factors create such local fossil bonanzas, widely known by the German Konservat Lagerstätten (preservational storage places, Seilacher et al., 1985): rapid burial (obrution), stagnation (eutrophic anoxia), fecal pollution (septic anoxia), bacterial sealing (microbial death masks), brine pickling (salinization), mineral infiltration (permineralization and nodule formation by authigenic cementation), incomplete combustion (charcoalification), desiccation (mummification) and freezing (Martin, 1999). The key to preserving articulated fossils is to prevent later disturbance of the corpse or exuviae by scavengers, burrowers, or sedimentary reworking. Even more paleobiological information is preserved if microbial decomposers are denied access to organic matter (Gaines et al., 2008). Preservation of decay-resistant lignin of wood and cuticle of plant leaves (van Bergen et al., 1995; Mösle …