Abstract
Earth’s Critical Zone (CZ), the near-surface layer where rock is
weathered and landscapes co-evolve with life, is profoundly influenced
by the type of underlying bedrock. Previous studies employing the CZ
framework have focused almost exclusively on landscapes dominated by
silicate rocks. However, carbonate rocks crop out on approximately 15%
of Earth’s ice-free continental surface and provide important water
resources and ecosystem services to ~1.2 billion people.
Unlike silicates, carbonate minerals weather congruently and have high
solubilities and rapid dissolution kinetics, enabling the development of
large, interconnected pore spaces and preferential flow paths that
restructure the CZ. Here we review the state of knowledge of the
carbonate CZ, exploring parameters that produce contrasts in the CZ in
different carbonate settings and identifying important open questions
about carbonate CZ processes. We introduce the concept of a
carbonate-silicate CZ spectrum and examine whether current conceptual
models of the CZ, such as the conveyor model, can be applied to
carbonate landscapes.We argue that, to advance beyond site-specific
understanding and develop a more general conceptual framework for the
role of carbonates in the CZ, we need integrative studies spanning both
the carbonate-silicate spectrum and a range of carbonate settings.