Emergence and evolution of Santa Maria Island (Azores)—The conundrum of uplifted islands revisited
Ricardo S. Ramalho
George Helffrich
José Madeira
Michael Cosca
Christine Thomas
Rui Quartau
Ana Hipólito
Alessio Rovere
Paul J. Hearty
Sérgio P. Ávila
Abstract
The growth and decay of ocean-island volcanoes are intrinsically linked to vertical movements. While the causes for subsidence are better understood, uplift mechanisms remain enigmatic. Santa Maria Island in the Azores Archipelago is an ocean-island volcano resting on top of young lithosphere, barely 480 km away from the Mid-Atlantic Ridge. Like most other Azorean islands, Santa Maria should be experiencing subsidence. Yet, several features indicate an uplift trend instead. In this paper, we reconstruct the evolutionary history of Santa Maria with respect to the timing and magnitude of its vertical movements, using detailed field work and 40Ar/39Ar geochronology. Our investigations revealed a complex evolutionary history spanning ∼6 m.y., with subsidence up to ca. 3.5 Ma followed by uplift extending to the present day. The fact that an island located in young lithosphere experienced a pronounced uplift trend is remarkable and raises important questions concerning possible uplift mechanisms. Localized uplift in response to the tectonic regime affecting the southeastern tip of the Azores Plateau is unlikely, since the area is under transtension. Our analysis shows that the only viable mechanism able to explain the uplift is crustal thickening by basal intrusions, suggesting that intrusive processes play a significant role even on islands standing on young lithosphere, such as in the Azores.
Ramalho R.S., Helffrich G., Madeira J., Cosca M., Thomas C., Quartau R., Hipólito A., Rovere A., Hearty P.J. and Ávila S.P. (2017) Emergence and evolution of Santa Maria Island (Azores)—The conundrum of uplifted islands revisited. Geological Society of America Bulletin 129(3-4): 372-390. 10.1130/B31538.1
@article{Ramalho2017,
Title = {Emergence and evolution of Santa Maria Island (Azores)—The conundrum of uplifted islands revisited},
Author = {Ramalho, Ricardo S. and Helffrich, George and Madeira, José and Cosca, Michael and Thomas, Christine and Quartau, Rui and Hipólito, Ana and Rovere, Alessio and Hearty, Paul J. and Ávila, Sérgio P.},
Editor = {},
Journal = {Geological Society of America Bulletin},
Year = {2017},
Pages = {372-390},
Volume = {129},
Doi = {10.1130/B31538.1},
Abstract = {The growth and decay of ocean-island volcanoes are intrinsically linked to vertical movements. While the causes for subsidence are better understood, uplift mechanisms remain enigmatic. Santa Maria Island in the Azores Archipelago is an ocean-island volcano resting on top of young lithosphere, barely 480 km away from the Mid-Atlantic Ridge. Like most other Azorean islands, Santa Maria should be experiencing subsidence. Yet, several features indicate an uplift trend instead. In this paper, we reconstruct the evolutionary history of Santa Maria with respect to the timing and magnitude of its vertical movements, using detailed field work and 40Ar/39Ar geochronology. Our investigations revealed a complex evolutionary history spanning ∼6 m.y., with subsidence up to ca. 3.5 Ma followed by uplift extending to the present day. The fact that an island located in young lithosphere experienced a pronounced uplift trend is remarkable and raises important questions concerning possible uplift mechanisms. Localized uplift in response to the tectonic regime affecting the southeastern tip of the Azores Plateau is unlikely, since the area is under transtension. Our analysis shows that the only viable mechanism able to explain the uplift is crustal thickening by basal intrusions, suggesting that intrusive processes play a significant role even on islands standing on young lithosphere, such as in the Azores.},
}
TY - JOUR
AU - Ramalho, Ricardo S.
AU - Helffrich, George
AU - Madeira, José
AU - Cosca, Michael
AU - Thomas, Christine
AU - Quartau, Rui
AU - Hipólito, Ana
AU - Rovere, Alessio
AU - Hearty, Paul J.
AU - Ávila, Sérgio P.
TI - Emergence and evolution of Santa Maria Island (Azores)—The conundrum of uplifted islands revisited
T2 - Geological Society of America Bulletin
PY - 2017
SP - 372-390
VL - 129
DO - 10.1130/B31538.1
AB - The growth and decay of ocean-island volcanoes are intrinsically linked to vertical movements. While the causes for subsidence are better understood, uplift mechanisms remain enigmatic. Santa Maria Island in the Azores Archipelago is an ocean-island volcano resting on top of young lithosphere, barely 480 km away from the Mid-Atlantic Ridge. Like most other Azorean islands, Santa Maria should be experiencing subsidence. Yet, several features indicate an uplift trend instead. In this paper, we reconstruct the evolutionary history of Santa Maria with respect to the timing and magnitude of its vertical movements, using detailed field work and 40Ar/39Ar geochronology. Our investigations revealed a complex evolutionary history spanning ∼6 m.y., with subsidence up to ca. 3.5 Ma followed by uplift extending to the present day. The fact that an island located in young lithosphere experienced a pronounced uplift trend is remarkable and raises important questions concerning possible uplift mechanisms. Localized uplift in response to the tectonic regime affecting the southeastern tip of the Azores Plateau is unlikely, since the area is under transtension. Our analysis shows that the only viable mechanism able to explain the uplift is crustal thickening by basal intrusions, suggesting that intrusive processes play a significant role even on islands standing on young lithosphere, such as in the Azores.
ER -
