The crustal structure of the Canary Basin: Accretion processes at slow spreading centers

Abstract

Abstract. Multichannel seismic reflection and gravity data define the structure of Mesozoic ocean crust of the Canary Basin, formed at slow spreading rates. Single and multichannel seismics show a transition from smooth to rough basement topography from Jurassic to Cretaceous crust and a coeval change in crustal structure. Internal reflectivity of the rough basement area comprises upper, upper middle or whole crust cutting discrete dipping reflections. Lower-crustal reflectivity is almost absent and reflections from the crust-mantle transition are short and discontinuous or absent for several kilometers. In contrast, crust in the smooth basement area is characterized by sparse lower crustal events and common reflections from the crust-mantle boundary. The crustal structure of fracture zones in the rough basement area is associated with depressions in the basement top and in most cases with thin crust. In the smooth basement area, fracture zones exhibit neither a clear topographic expression nor crustal thinning. We interpret these characteristics as indicative of an increase in extensional tectonic activity and decrease in magmatic activity at the spreading ridge associated with a general decrease of spreading rate from Jurassic to Cretaceous times. In addition, the crust imaged across the path of the Cape Verde Hot Spot in the Canary Basin exhibits a widespread lower crustal reflectivity, very smooth topography and apparently thick crust. Our data document significant changes in the structure of crust formed at slow spreading rates which we attribute to thermal changes in the lithosphere due either to variations in spreading rate or to the presence of a hot spot beneath the Mesozoic Mid-Atlantic Ridge.

On the roughness of Mesozoic oceanic crust in the western North Atlantic

“…1993); (b) Blake Spur lines 721 (after 148 Ma) and 714 (Morris et al . 1993); (c) part of Canary Basin line C (Ranero et al . 1997), with arrows marking approximate locations of fracture zone crossings; (d) OCEANS line 10 (Henstock et al .…”

“…A: Blake Spur Fracture Zone (Morris et al . 1993); B: west flank of the Mid‐Atlantic Ridge at 28°N; C: Canaries line C (Ranero et al . 1997); D: OCEANS area (Henstock et al .…”

Tilt Observations in the Normal Mode Frequency Band at the Geodynamic Observatory Cueva de los Verdes, Lanzarote

“…The Canary Islands are an old volcanic structure sited on top of the Jurassic oceanic crust. Their origin is still under discussion and therefore several geophysical research projects have been conducted in the archipelago (e.g., BOSSHARD and MACFARLANE, 1970;BANDA et al, 1981;CANALES and DANOBEITIA, 1998;DANOBEITIA et al, 1994;RANERO et al, 1997). A number of genetic models has been proposed for this region, for instance, the hotspot theory (WILSON, 1973) or the connection to the Alpine orogeny, which reached its maximum activity in this zone during the Miocene (ANGUITA and HERNAN 1975).…”

Metasedimentary xenoliths in the lavas of the Timanfaya eruption (1730–1736, Lanzarote, Canary Islands): metamorphism and contamination processes

“…The Canary Island crust has been extensively studied (Banda et al 1981(Banda et al , 1992Suriñach, 1986;Ranero & Banda, 1997;Watts, 1994;Watts et al 1997;Schmincke et al 1998;Collier & Watts, 2001;Krastel & Schmincke, 2002). At Lanzarote the crust is 11 km thick (Suriñach, 1986).…”