Final answer:
Ocean sediments are not thickest in pelagic waters overlying the oceanic ridges, but rather closer to continental margins. The incorrect statement among the options given about ocean sediments is A. The other statements concerning the composition and formation of ocean sediments are correct.
Step-by-step explanation:
The statement among the options that is false concerning ocean sediments is: A. Ocean sediments are thickest in pelagic waters overlying the oceanic ridges. This statement is incorrect because sediments are typically thinner over oceanic ridges due to the continuous geological activity that occurs there, such as the formation of new crust. In contrast, ocean sediments are generally thicker near continental margins where the sediment is delivered from rivers and eroded material from the land. Pelagic sediments, further out in the open ocean, tend to be much finer and are composed of microscopic organisms' shells or chemical precipitates.
Ocean sediments can be composed of various substances, such as chemical precipitates like calcium carbonate or manganese dioxide, and organic remnants, which include the fossilized remains of ancient marine life and remains of living organisms that fall to the ocean floor, including foraminifera, coccolithophores, and diatoms. Furthermore, ocean sediments can contain cosmic materials like ancient meteoritic debris. Therefore, options B, C, D, and E are all true regarding ocean sediments.
The formation of sedimentary rocks, including those found in the ocean, involves processes of weathering, erosion, deposition, and the cementation of particles. The source of these particles can be terrestrial or marine, and sometimes, they form from the chemical precipitation of minerals in the water, as seen with the formation of salt from evaporating water bodies or the accumulation of marine organism shells to form limestone.