CONTINGENT EVENTS THROUGH THE PRECAMBRIAN AND THEIR SIGNIFICANCE FOR A REVISED GEOLOGICAL TIMESCALE

A compilation of geotectonic and geobiological events through the Precambrian reveal a causally connected series of unique events (directionality) that were dependent (contingent) upon those that came before, giving a directionality to time’s arrow over the 4 billion years of Earth history that preceded the Cambrian explosion (see Gould, 1994).

In this paper, I outline these events, and show how changes in the biosphere can be linked to changes in the geodynamics of the Earth, driven ultimately by varying heat output from the core and mantle in response to secular decline in heat production and the supercontinent cycle. Evolutionary development may relate to selective pressures driven by the unavailability of various molecular components and/or trace metals as nutrients.

Changes in the biosphere were effected at an order of magnitude faster rate than changes in the Earth geodynamic system, providing opportunities to use their imprint in the rock record as “Golden spikes” (GSSPs) for a revised Precambrian timescale. A scheme is presented of how these changes can be used to create a more natural Precambrian timescale that is based on the actual rock record (Bleeker, 2004) and that provides a much more compelling picture of the early development of our planet.

Bleeker, W., 2004b. Towards a “natural” time scale for the Precambrian — A proposal. Lethaia, 37: 1–4.

Gould, S.J., 1994. Introduction: The coherence of history. In: Bengston, S. (ed.), Early Life on Earth. Nobel Symposium 84, 1–8.