Holocene tectonic uplift of the St Peter and St Paul Rocks (Equatorial Atlantic) consistent with emplacement by extrusion

• Published in: Marine geology Vol. 271; no. 1; pp. 177 - 186
• Main Authors: Campos, Thomas F.C., Bezerra, Francisco H.R., Srivastava, Narendra K., Vieira, Marcela M., Vita-Finzi, Claudio
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.05.2010
• Subjects: Holocene; Marine; marine terrace; Mid-Atlantic Ridge; peridotite; sea-level change; uplift; AS, Equatorial Atlantic; A, Mid-Atlantic Ridge; peridotite; uplift; Holocene; marine terrace; sea-level change; Mid-Atlantic Ridge
• ISSN: 0025-3227; 1872-6151
• DOI: 10.1016/j.margeo.2010.02.013

St Peter and St Paul Rocks (SPSPR) are emergent portions of a peridotitic mass within the St Paul fracture zone of the Equatorial Mid-Atlantic Ridge, where local seismicity is dominated by strike-slip mechanisms. We used subtidal red algae in living position, death assemblages in intertidal conglomerates, and marine terraces as sea-level markers. The highest deposits correspond to a marine terrace with a shoreline angle at 8 ± 1 m asl that formed ca. 6400–6200 cal. yr BP. After correction for the sea-level changes derived by glacioisostatic modelling, AMS and radiometric 14C age measurements on the Holocene sea-level markers indicate emergence during the last 6600 a at a minimum average rate of ∼ 1.5 mm/a. We propose that uplift resulted from peridotite emplacement by extrusion, rather than volcanic activity or fault slip, with the implication that the ridge has been subject to compression during the Holocene.