Rhodolith beds are distributed from the north­ eastern to the southeastern Brazilian continental shelf, constituting the largest extension of coralline algal de­ posits in the world. Little is known about the deep rho­ dolith beds within the Campos Basin: the largest oil pro­ duction area in the country and a priority area for marine life conservation. This study illustrates a deep rhodolith bed covering about 15 km 2 of a 40 km 2 ­area in the Peregrino oil field sampled at 100-106 m water depth. Coralline algae are the dominant components on the living rhodolith surfaces associated with subordinate bryozoans, cnidarids, brachiopods and porifers. In some inner parts of the coralline algal nodules, encrusting acervulinid fora­ minifera are the main nodule contributors. Through accel­ erator mass spectrometric analysis, radiocarbon age esti­ mates show that the range in ages between the living outer rhodolith parts and within 3 mm from it the rhodoliths is ca. 4,700 years. This suggests that a proportion of fossil rhodoliths had been recolonized after periods of burial and/or erosion. The present­day Peregrino rhodolith bed played a fundamental ecological role in the Brazilian con­ tinental shelf's benthic habitats for thousands of years.