Macrostratigraphy: Insights into Cyclic and Secular Evolution of the Earth-Life System

Abstract

Rocks in Earth's crust are formed, modified, and destroyed in response to myriad interactions between the solid Earth (tectonics, geodynamics), the fluid Earth (ocean-atmosphere, cryosphere), and the living Earth (evolution, biochemistry). As such, the geological record is an integrator of geological, biological, and climatological processes and their histories. Here we review contrasting perceptions of the processes that govern the formation and destruction of the geological record, beginning with the relationship between macroevolutionary patterns in the fossil and sedimentary rock records and culminating with contrasting models of rock cycling. Using the approach of macrostratigraphy, we present an integrated summary of the quantity-age properties of rocks in continental and oceanic crust. The predominant process signal in the rock quantity-age distribution in continental crust is one of episodic growth, whereas in oceanic crust it is one of continual destruction. Relatively abrupt shifts in the dominant locus of sediment deposition, from fast-cycling oceanic crust to long-term continental reservoirs, and attendant expansions and contractions in the area of crust that is emergent, are correlated in timing and magnitude with shifts in the concentration of oxygen in the atmosphere and major macroevolutionary transitions in the biosphere. The most recent of possibly two such first-ordertransitions occurred at the start of the Phanerozoic and is marked by a prominent preserved geomorphic surface known as the Great Unconformity. ▪ Macrostratigraphy uses the bulk characteristics of the rock record to probe the evolution of the Earth system. ▪ Quantifying the creation and destruction of rock units can illuminate the long-term evolution of continents and the life that inhabits them.