Side-scan sonar characteristics and manganese nodule abundance in the Clarion-Clipperton fracture zones, NE equatorial Pacific

Lee, S.H. and Kim, K.H. (2004) Side-scan sonar characteristics and manganese nodule abundance in the Clarion-Clipperton fracture zones, NE equatorial Pacific. Marine Georesources and Geotechnology, 22 (1-2), 103-114. (doi:10.1080/10641190490473434).

Abstract

The deep ocean floor between the Clarion and Clipperton fracture zones (NE
equatorial Pacific) has the highest known manganese nodule abundance in the world oceans. A detailed analysis of MR1 (Mapping Researcher 1, 11–12 kHz) sonar images and free-fall grab data in the Korean manganese nodule field areas reveals a
close relationship between side-scan sonar characteristics of the seafloor and manganese nodule abundance. Eight sonar facies are identified based on back-scattering intensity and distribution patterns. These sonar facies can be interpreted as (1) volcanic seamounts (facies I-1), (2) bounding faults of abyssal hills (facies I-2 and II-1), (3) lava flows or volcanoclastic mass-flow deposits around the volcanic
seamounts (facies I-3 and II-2), (4) crests of abyssal hills (facies II-1), (5) abyssal
troughs between abyssal hills (facies III-1), (6) relatively flat areas (facies II-3 and
III-2). In the areas where facies II-1 (abyssal hill crests with thin sediment cover)
and II-3 (relatively flat areas draped by thin sediments) are dominant, manganese
nodules occur abundantly. In contrast, zones comprising facies III-1 (abyssal
troughs with thick sediment cover) and III-2 (relatively flat areas covered by thick
sediments) are characterized by low abundance of manganese nodules. This relationship between distribution of sonar facies and manganese nodule abundance
implies that (1) the qualitative difference in acoustic reflectivity of long-range sidescan sonar with some ground truth data is useful for regional assessment of manganese nodule occurrence over wide areas in a reasonable time, and (2) seafloor topography and sediment thickness are important controlling factors for regional occurrences of manganese nodules.

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