Introduction

In previous chapters the characteristics and development of different sectors of the Great Barrier Reef (GBR) have been discussed largely on a spatial division – inter-reef shelf (Chapter 6), fringing and nearshore reefs (Chapter 7), mid-shelf reefs (Chapter 8), shelf-edge reefs (Chapter 9), and reef islands (Chapter 10). Chapter 11 derived rates of process from the data of previous chapters and provided some of the basics of the chronological framework used in this chapter, which attempts to provide a holistic rather than sectorial evolution of the GBR. Different processes clearly will be occurring simultaneously on different parts of the reef which may interact with each other. The driving force for the development of the reef, and the coast and shelf in general has been the postglacial rise in sea level, the basics of which were established in Chapter 3. This chapter looks at the changing geomorphology as sea level rose from its absolute low of about − 125 m 20 000 years ago at what are regarded as critical stages in the transgression. Initially sea level rose against a steeply sloping shoreline. Subsequently the antecedent Pleistocene reefs of the outer shelf became limestone islands before becoming submerged and developing their Holocene veneer. A completely different geomorphology existed on what is now the wide gently sloping shelf between the outer reef and mainland. Rates of shoreline change were rapid until the stillstand of the last 6.5 ka.