High-precision U-series ages of transported coral blocks on Heron Reef (southern Great Barrier Reef) and storm activity during the past century

Transported coral blocks scattered on reef flats have previously been identified as useful proxies for past storm occurrences. High-precision TIMS U-series dating and detailed field observations of 110 coral samples collected from 102 individual transported coral colonies (coral blocks) and 4 transported sections of reef matrix (reef blocks) from the northern side of Heron Reef (southern Great Barrier Reef) indicate that: (1) the youngest age of corals attached to reef blocks may represent the age of possible past storm occurrence, providing a proxy for historical storm reconstruction; (2) most ages of dated storm-transported coral and reef blocks match well relatively with known cyclone and storm events, further supporting that they are good indicators of past storm events; and (3) age distribution and relative probability frequency analysis of the dated coral and reef blocks suggest that there have been eight broad periods of storm occurrence since 1900 AD (1904–1909, 1914–1916, 1935–1941, 1945–1960, 1965–1967, 1976–1977, 1983–1988 and 2001–2007), roughly showing decadal variations. The coral-based storm reconstruction therefore extended the database of past storm occurrences around Heron Reef area. These findings suggest that coral reefs in the southern Great Barrier Reef are frequently influenced by periods of high storm activity, and show strong resilience to natural disturbances over the past century. Additionally, our results show for the first time that the blue skeletal coral Heliopora coerulea (Order: Helioporacae) has U concentrations of only 0.12 to 0.30 ppm, ~ 5–10% that of common reef building corals with white skeletons (Order: Scleractinia), which may be a unique chemical signature of the only living species of the Helioporidae family.

► The youngest age of corals attached to reef blocks is a proxy for past storm.
► Surface ages of well-preserved coral blocks are good indicators of past storm events.
► 106 block ages suggest eight broad periods of storm occurrence over last 100 years.
► U concentration of blue skeletal coral Heliopora coerulea is ~ 5–10% of Scleractinia.