Subaerial exposure environment

Exposure surfaces occur on land and under the sea, but in this chapter we are concerned only with subaerial exposure surfaces. More specifically we are concerned with the effects of subaerial exposure on carbonate sequences. Subaerial exposure surfaces are areas where upper bounding surfaces of sediment or rock show the effects of being exposed at the Earth’s surface. In order to recognize fossil subaerial exposure surfaces they need to be exposed long enough to allow subaerial diagenetic processes to modify or obliterate pre-existing fabrics. This will be recorded as a break in the sedimentary sequence. This usually means that significant periods of time have passed before exposed surfaces are buried by new deposits. What we mean by significant periods of time is a relative concept dependent on our limits of resolution and powers of observation. When considering absolutes of time we will offer only abstracts; our intention here is not to quantify absolutes of timing, duration or intensity of processes acting upon exposure surfaces, nor to examine critically the processes themselves. Rather we will document common and characteristic products of subaerial exposure, list criteria which aid in recognition of fossil subaerial exposure surfaces, and point out the significance and economic importance of subaerial exposure surfaces in ancient carbonate sequences.

Adhering to this outlined conceptual framework we can define a subaerial exposure surface as a distinct surface on land which indicates: (1) non-deposition and commonly erosion; and