Buried trees and basin tectonics: A discussion

Abstract

Rooted tree trunks up to 12m tall, buried in growth position, are a feature of Euramerican late Carboniferous Coal Measures. They provide evidence of episodes in which generation of accommodation space, and resultant sediment accumulation, occurred at rates far in excess of the net long-term (cm/kyr) rates for the sections in which they occur; and they do so in a variety of tectonic settings. Episodic, metre-scale, co-seismic subsidence is the likeliest explanation for this phenomenon. Such episodic subsidence is unlikely to be a unique tectonic attribute of Carboniferous Coal Measure basins. Instead, it seems that the trees’ morphology and ecology uniquely favoured their preservation as casts in growth position, thus providing a yardstick for the scale and rapidity of the co-seismic subsidence and accumulation. Other epicontinental shallow marine/paralic basins lack this means of gauging of the rate of subsidence, but it is possible that most of them also experienced episodic subsidence events. Such events would explain the capture of records of, for example, high-energy beach deposition and tidal sedimentation. They also suggest the need for a reappraisal of the significance of metre-scale parasequences in both siliciclastic and carbonate rocks.