[Haberland] Seismic site characterization of the proposal ICDP drilling project in the Baza Basin (Southern Spain)

German Title: Seismic site characterization of the proposal ICDP drilling project in the Baza Basin (Southern Spain)

Abbreviation: 318

Current Status: completed


Main Applicant:Dr. Christian Haberland


Resources Recipient


Other Persons

Manfred Stiller
Prof. Dr. Dieter F. Mertz


Conveyor Begin:
Conveyor End:
Conveyor Duration:
Year: 2013


Description

Proposal:

The intra-mountain Baza Basin in Southern Spain is the largest of the Late Neogene continental basins of the Betic Cordillera. It provides an up to 2.5 km thick archive of lacustrine and ancillary continental deposits from the Late Miocene to Middle Pleistocene. Infilling of the Baza Basin proceeded mainly by deposition of fine-grained deposits arranged in concentric facies belts in a lake complex. The expansion and contraction of these nested paleoenvironments serve as highly sensitive indicators of climate change which makes the Baza Basin a unique site for an integrated paleoclimate-oriented study of the last 7Ma of SE Europe. The planned LARSEI drilling project (LAcustrine Record of SE Iberia; submitted pre-proposal to ICDP) proposes to drill the Baza evaporitic basin in order to establish a realistic paleo-climatic record through the final Neogene (including the entire Pliocene) that very likely reflects regional events in the western Mediterranean as well as global climate milestones. Prerequisite for the drilling activities is the profound knowledge of the basin structure and local zones of neo-tectonic deformation, mainly related to the Baza fault bounding the basin to the West. We propose to aquire seismic multichannel profiles providing high-resolution images of the basin and related structural units (i.e. faults). The results of these measurements will both help to guide the drilling activities (including drilling site selection; presite study) and to better understand the structure and evolution of the Baza basin.

 

Results:

The intra-mountain Baza Basin in Southern Spain is the largest of the Late Neogene continental basins of the Betic Cordillera. It provides an up to 2.5 km thick archive of lacustrine and ancillary continental deposits from the Late Miocene to Middle Pleistocene. Infilling of the Baza Basin proceeded mainly by deposition of fine-grained deposits arranged in concentric facies belts in a lake complex. The expansion and contraction of these nested paleoenvironments serve as highly sensitive indicators of climate change which makes the Baza Basin a unique site for an integrated paleoclimate-oriented study of the last 7 Ma of SE Europe. The planned LARSEI drilling project (LAcustrine Record of SE Iberia) proposes to drill the Baza evaporitic basin in order to establish a realistic paleo-climatic record through the final Neogene (including the entire Pliocene) that very likely reflects regional events in the western Mediterranean as well as global climate milestones. In order to reveal the subsurface of the Baza Basin, both to understand the tectono-stratigraphic evolution of the intramontane Baza Basin and pre-site survey for future drilling activities, we acquired three reflection seismic lines (each 18 km long; vibroseis method). We applied rather conventional CDP data processing and calculated velocity models from first arrival P-wave tomography. The images show the highly asymmetric structure of the basin. The sediments thicken westward approaching the main governing Baza fault system (BFS), reaching a maximum observed thickness of >2200m. Three major seismic units (including several subunits) on top of the acoustic basement could be identified. We use stratigraphic information from the uplifted block of the BFS and other outcrops at the basin edges together with available information from neighboring Bétic basins to correlate the seismic units to the known stratigraphy in the area. The seismic units could be associated to Tortonian marine deposits, and latest Miocene to Pleistocene continental fluvio-lacustrine sediments. Individual strands of the BFS dip approximately ~45°E and truncate the basin sediments. Fault reflections were imaged in two lines owing to the large impedance contrast between sedimentary fill and basement. In the central part of the basin several basement faults can be identified which document strong deformation in the early stages of basin formation. Some of these faults can be traced up to the surface indicating activity until present times. The results of our study provide detailed information for future scientific drilling activities in the region. The seismic images revealed large regions with continuous and to large extent undisturbed continental deposits, particularly in the northwest of the covered region. Furthermore, the images show segments along the seismic lines where the continental deposits are thickest which will be helpful for the selection of a future drill site.