adjacent to North America’s Cretaceous Western Interior Seaway) (Robinson Roberts and Kirschbaum 1995) and in lakes (for example in China) (Shao et al. 2020). This plant matter was buried and subsequently formed coal measures. The thickest, most extensive Upper Cretaceous coals of the Western Interior of North America are associated with a time of mountain building, folding and thrusting in the Western Cordillera. The distribution of conglomerates and volcaniclastics indicate high-energy river systems flowing from the adjacent mountain front towards the Western Interior Seaway (Robinson Roberts and Kirschbaum 1995). The Paleogene Powder River Basin of the western USA contains the largest reserves of low sulfur sub-bituminous coal in the world (Clarey 2017). Low sulfur is generally an indicator of a freshwater, rather than marine water, depositional environment (Sari et al. 2017). In association with the mountain-building event known as the Laramide Orogeny (which uplifted much of the Rocky Mountains), vegetation was transported by rivers to broad floodplains and around lake margins. Basin subsidence and runoff from adjacent mountain ranges contributed to thick accumulations of sediment. The plant matter then became preserved as thick coal seams (Glass 1980). The fossil record of inferred lacustrine settings indicates biodiversification from the Mesozoic onwards (Buatois et al. 2016). Post-Paleozoic coal in China is commonly interpreted by Chinese researchers to be associated with lacustrine basins (Dai et al. 2020; Li et al. 2018). Early–Middle Jurassic coal-bearing basins are inferred to have been large and medium-sized inland lake basins, in which alluvial-lake Figure 13. First vertical derivative of total magnetic intensity indicating Cretaceous basalt distribution in paleovalleys of southwestern Australia (after Olierook et al. 2015). The basalt is columnar rather than pillow in form, and together with occurrence in river valleys, subaerial extrusion is evident. Figure 14. An idealized schematic diagram showing a representation of post-Paleozoic depositional environments including continental intermontane lacustrine, alluvial plain, coastal plain, river and delta plain (Dai et al. 2020). These are dominantly non-marine settings. basalt. The post-Paleozoic was characterised by a great variety of depositional settings, including both non-marine and marine settings (Dickens 2022) (Fig. 14). When the opening of today’s oceans was underway, there was also continental mountain building, on active continental margins. Significant thick Mesozoic and Cenozoic sedimentary sequences formed with successive episodes of runoff from these mountains. Plants better suited to a drier land environment grew and became dominant (Fig. 7). Plants were transported by runoff from tectonically active mountain areas and buried in near-coastal environments (such as DICKENS Flood Waters Lead to Seafloor Spreading 2023 ICC 459
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