Marine Geophysics and Hydroacoustics

NICA-BRIDGE, Lakes in Nicaragua

Seismic reconnaissance survey for the ICDP proposal ‘Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans

 

Summary

The two largest lakes in Central America, Lake Nicaragua and Lake Managua, are situated in the south-central part of Nicaragua. The location and the proposed long existence (at least Pliocene possibly Late Miocene) make these lakes promising targets for scientific drilling within the International Continental Drilling Program. more

map

Location of the Nicaraguan lakes within Central America. MAT= Middle American Trench. The arrow represents the Cocos Plate motion vector. The black dashed line marks the proposed track of the new Nicaragua channel connecting the Caribbean Sea with the Pacific through Lake Nicaragua; the white dashed line outlines the Nicaraguan Depression. Blue box indicate the Tertiary Coyol arc. Numbers mark volcanoes at the Quaternary volcanic front, which all generated late Pleistocene to Holocene highly explosive eruptions.

Drilling objectives include therefore

  1. recovery and extension of a Neotropic paleo-climate record into the past,
  2. investigation of marinelacustrine interactions in the past (connections to the oceans), in the recent, and the future (channel construction),
  3.  the history of long tectonic and sedimentary basin (lake) development,
  4. arc evolution and related hazards,
  5. deciphering their significance as an endemic hot spot over time,
  6. investigation of an important paleozogeographic event, the great American biotic interchange, and
  7. the ability to combine seismology, volcanology, paleoclimate, paleoecology, and paleoenvironment in one project.

 

Hence, a group of scientists submitted an ICDP workshop proposal with  the aim to develoboatp a scientific drilling project focused on Lakes Nicaragua and Managua. The proposal was generally well received but noted a significant lack of seismic data. Only very sparse seismic data have been collected in the past but failed to image the deeper subsurface due to technical problems during data acquisition and complicated depositional conditions (e.g., gas and tephras). Hence, the workshop proposals were not accepted at the current stage. In order to support the proposal, we are currently acquiring
reconnaissance seismic data of Lake Nicaragua. 

The seismic survey was carried out from 17.02 - 03.03.2017. The Nicaraguan Navy provided the vessels (see photo in the middle). We used a Micro-GI Gun (0.1 l primary volume) as source for the reflection seismic survey. Air was produced by two mobile diving compressors. The energy was recorded by a 50m-long 32-channel  digital geometrics GeoEel streamer. Two profiles were shot with a larger airgun in order to record refractions with a Mini-OBS. Sediment echo sounderadata were recorded with an Innomar system. In total, we collected about 350 km of seismic and echo sounder profiles.

Large parts of the Lake show a very high impedance reflector with a negative polarity at the lake floor, which is very difficult to penetrate. This is most likely caused by free (volcanic) gases in the sediments close to the lake floor. However, some windows to the deeper sub-surface do exist, which show significantly reduced multiple strength and partly well-stratified sedimentary successions (see seismic section above, location marked on track chart in red).

seismic

innomar

They represent an interlayering of volcaniclastic and lacustrine sediments. Lateral accumulation rates seem to vary significantly. This is also visible on sediment echo sounder data. The next step is the full processing of the newly acquired data. Special focus will be on the multiple suppression using ‚Adaptive Surface‐Related Multiple Elimination'- techniques using VISTA2016. The fully processed data will be used for a stratigraphic interpretation. Results of the survey will be included in a revised ICDP workshop proposal to be submitted early next year. If successful, we will do a full pre-site survey acquiring additional data of Lake Nicaragua and also including Lake Managua, which is proposed as potential second drilling target.

Persons to contact:  Elodie Lebas, Sebastian Krastel

Forschungsfahrt:

February - March 2017, Multichannel seismic Survey

Partnerinstitute und beteiligte Personen:

  • Katlina Hagemann (Uni Kiel)
  • Dr. Steffen Kutterolf (Geomar Kiel)
  • Wilfried Strauch (Institutio Nicaragüense de Estudios Territoriales, Managua Nicaragua)

 

Publikationen:

  • S. Krastel, E. Lebas, S. Kutterolf, K. Hagemann, W. Strauch (2017). Seismic reconnaissance survey for the ICDP proposal 'Paleoclimate, Paleoenvironment, and Paleoecology of Neogene Central America: Bridging Continents and Oceans (NICA-BRIDGE)'IODP/ICDP Colloquium, 14-16th March, Braunschweig, Germany