Abrupt global events in the Earth's history: a physics perspective

The timeline of the Earth's history reveals quasi-periodicity of the geological record over the last 542 Myr, on timescales close, in the order of magnitude, to 1 Myr. What is the origin of this quasi-periodicity? What is the nature of the global events that define the boundaries of the geological time scale? I propose that a single mechanism is responsible for all three types of such events: mass extinctions, geomagnetic polarity reversals, and sea-level fluctuations. The mechanism is fast, and involves a significant energy release. The mechanism is unlikely to have astronomical causes, both because of the energies involved, and because it acts quasi-periodically. It must then be sought within the Earth itself. And it must be capable of reversing the Earth's magnetic field. The last requirement makes it incompatible with the consensus model of the origin of the geomagnetic field - the hydromagnetic dynamo operating in the Earth's fluid core. In the second part of the paper, I show that a vast amount of seemingly unconnected geophysical and geological data can be understood in a unified way if the source of the Earth's main magnetic field is a ~200-km-thick lithosphere, repeatedly magnetized as a result of methane-driven oceanic eruptions, which produce ocean flow capable of dynamo action. The eruptions are driven by the interplay of buoyancy forces and exsolution of dissolved gas, which accumulates in the oceanic water masses prone to stagnation and anoxia. Polarity reversals, mass extinctions, and sequence boundaries are consequences of these eruptions. Unlike the consensus model of geomagnetism, this scenario is consistent with the paleomagnetic data showing that "directional changes during a [geomagnetic polarity] reversal can be astonishingly fast, possibly occurring as a nearly instantaneous jump from one inclined dipolar state to another in the opposite hemisphere".Comment: Final journal version. New title, significant changes. Supersedes v.

Sequence Stratigraphy of the Cenozoic Pannonian Basin, Hungary

pages 390 and 396 are missing from text.The sequence stratigraphy of the middle Eocene-Pliocene of the Pannonian Basin permits to differentiate fifty-nine depositional sequences. An earlier compressional Paleogene basin in the central and eastern Pannonian Basin is unconformably overlain by a Neogene extensional basin. Tectonic regimes interacted with transgressive-regressive facies cycles. The boundaries of these cycles coincide with regional stage boundaries. Unconformities separating these cycles mark the episodic closure of connections between the Pannonian Basin and the European epicontinental seas from Oligocene through middle Miocene time. The unconformities are the result of short-term glacio-eustatic falls, sometimes enhanced by tectonic events. Within the limits of biostratigraphic resolution during the Eocene-middle Miocene, many of the sequences of the Pannonian Basin correlate well with the sequences proposed by Haq et al. (1987). However, eight sequences, i.e. one in the Lutetian, three in the Bartonian, one in the Priabonian, one in the Rupelian and two in the Burdigalian, were not identified by Haq et al. (1987). The sequences and their boundaries are directly correlated with global oxygen isotope events. Glacioeustasy generates sequence boundaries beginning as early as the middle Eocene. Within the lacustrine setting of the Pannonian Basin (late Miocene- Pliocene time) relative lake level changes appear to control the overall sequence development. However, other minor variables, the sediment supply and the topography of the initial depositional surface were additional controlling factors. Thus differences in the physiography of the basin lead to totally different sequence types that all reflect to lake level fluctuations. In lateral direction, during a short time period, these lacustrine sequences are more sensitive to changes in the initial depositional profile and sediment supply