| Title | A new geological map of the Lau Basin (southwestern Pacific Ocean) reveals crustal growth processes in arc-backarc systems |
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| Author | Stewart, M S; Hannington, M D; Emberley, J; Baxter, A T; Krätschell, A; Petersen, S; Brandl, P A; Anderson, M O; Mercier-Langevin, P; Mensing, R; Breker, K; Fassbender, M L |
| Source | Geosphere vol. 18, no. 2, 2022 p. 910-943, https://doi.org/10.1130/GES02340.1  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20220098 |
| Publisher | The Geological Society of America |
| Document | serial |
| Lang. | English |
| Media | paper; digital; on-line |
| File format | pdf |
| Lat/Long WENS | -180.0000 -172.0000 -14.0000 -22.0000 |
| Subjects | stratigraphy; mapping techniques; lithostratigraphy; bathymetry; geophysical surveys |
| Illustrations | geological sketch maps; location maps |
| Released | 2022 02 11 |
| Abstract | A 1:1,000,000-scale lithostratigraphic assemblage map of the Lau Basin (southwestern Pacific Ocean) has been created using remote predictive mapping (RPM) techniques developed by geological surveys on
land. Formation-level geological units were identified in training sets at scales of 1:100,000-1:200,000 in different parts of the basin and then extrapolated to the areas where geological data are sparse. The final compilation is presented together
with a quantitative analysis of assemblage-level crustal growth based on area-age relationships of the assigned units. The data sets used to develop mapping criteria and an internally consistent legend for the compilation included high-resolution
ship-based multibeam, satellite- and ship-based gravity, magnetics, seafloor imaging, and sampling data. The correlation of units was informed by published geochronological information and kinematic models of basin opening. The map covers >1,000,000
km2 of the Lau-Tonga arc-backarc system, subdivided into nine assemblage types: forearc crust (9% by area), crust of the active volcanic arc (7%), backarc rifts and spreading centers (20%), transitional arc-backarc crust (13%), relict arc crust
(38%), relict backarc crust (8%), and undivided arc-backarc assemblages (<5%), plus oceanic assemblages, intraplate volcanoes, and carbonate platforms. Major differences in the proportions of assemblage types compared to other intraoceanic subduction
systems (e.g., Mariana backarc, North Fiji Basin) underscore the complex geological makeup of the Lau Basin. Backarc crust formed and is forming simultaneously at 12 different locations in the basin in response to widely distributed extension, and
this is considered to be a dominant pattern of crustal accretion in large arc-backarc systems. Accelerated basin opening and a microplate breakout north of the Peggy Ridge has been accommodated by seven different spreading centers. The result is an
intricate mosaic of small intact assemblages in the north of the basin, compared to fewer and larger assemblages in the south. Although the oldest rocks are Eocene (~40 m.y. old basement of the Lau and Tonga Ridges), half of the backarc crust in the
map area formed within the last 3 m.y. and therefore represents some of the fastest growing crust on Earth, associated with prolific magmatic and hydrothermal activity. These observations provide important clues to the geological evolution and makeup
of ancient backarc basins and to processes of crustal growth that ultimately lead to the emergence of continents. |
| Summary | (Plain Language Summary, not published)
This publication presents a detailed geological map of the Lau Basin (Tonga, Southwestern Pacific Ocean) and also describes the methods used to map at an
unprecedented resolution the geology of the seafloor. A quantitative analysis of the main geological units and associated rates of crustal growth is also presented. |
| GEOSCAN ID | 330169 |
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