000			02023nab a22002537a 4500
003			EC-PaCDF
005			20171127093831.0
008			170727t20122012xxu|||||||||||||||||eng|d
040			_aEC-PaCDF
041			_aeng
082	0	4	_221 _a551.4
100	1		_aPryet, A.
245	1	0	_aHydrogeological settings of a volcanic island (San Cristóbal, Galapagos) from joint interpretation of airborne electromagnetics and geomorphological observations.
520	0		_aMany volcanic islands face freshwater stress and the situation may worsen with climate change and sea level rise. In this context, an optimum management of freshwater resources becomes crucial, but is often impeded by the lack of data. With the aim of investigating the hydrogeological settings of southern San Cristóbal Island (Galapagos), we conducted a helicopter-borne, transient electromagnetic survey with the SkyTEM system. It provided unprecedented insights into the 3-D resistivity structure of this extinct basaltic shield. Combined with remote sensing and fieldwork, it allowed the definition of the first hydrogeological conceptual model of the island. Springs are fed by a series of perched aquifers overlying a regional basal aquifer subject to seawater intrusion. Dykes, evidenced by alignments of eruptive cones at the surface, correspond to sharp sub-vertical contrasts in resistivity in the subsurface, and impound groundwater in a summit channel. Combined with geomorphological observations, airborne electromagnetics are shown to be a useful for hydrogeological exploratory studies in complex, poorly known environments. They allow optimal development of land-based geophysical surveys and drilling campaigns.
546			_aEnglish
550			_a
700	1		_ad’Ozouville, N.
700	1		_aViolette, S. _91610
700	1		_aDeffontaines, B.
700	1		_aAuken, E.
773	0		_gVol. 16, (Dec 2012), p 4571–4579. _tHydrol. Earth Syst. Sci.
856			_uhttp://dx.doi.org/10.5194/hess-16-4571-2012
942			_2ddc _cARTICLE
999			_c13089 _d13089