Miocene—pliocene sea-level changes and volcanic phases on gran Canaria (Canary islands) in the light of new K—Ar ages

Abstract

Thirteen new K—Ar dates of stratigraphically important Pliocene and Pleistocene lava flows and intrusives from Gran Canaria (Canary Islands) permit a more precise definition of alternating periods of volcanic activity and erosional intervals. The Miocene erosional interval (Erosional Interval I) lasted from 9.6 to 4.4 m.y. B.P.; Roque Nublo volcanic activity (phase II in the magmatic history of the island) began 4.4 m.y. and ended 3.7 m.y. ago; Erosional Interval II lasted from 3.7 to 2.8 m.y. B.P.; volcanic activity resumed at 2.8 m.y. B.P. with the eruption of olivine nephelinite lavas. The subsequent alternation of phases of volcanic activity and erosional intervals is not yet precisely dated. Four regressions and three transgressions are recognized on Gran Canaria in the time interval 9.6-2 m.y. B.P. The famous marine sediments of the “Las Palmas Terrace” represent at least three distinct marine levels of different ages and only the oldest one may correspond to the age assignment “Helvetian or Tortonian” of Rothpletz and Simonelli (1890). Several causes for the marine transgressions are discussed such as eustatic changes in sea level, isostatic vertical movements of the island and movements in regional stress fields. None of the transgressions and regressions can be convincingly explained so far by either a single mechanism or a combination of several processes. However, we tentatively suggest that eustatic and, perhaps to a lesser degree, isostatic movements are the main causes. These uncertainties in the interpretation of the transgressions and regressions underscore the need for more precise dating of similar elevated marine sedimentary rocks on other Atlantic islands.