Question

Passage:
During the Challenger expedition (1872–1876), naturalists led by Sir Wyville Thomson conducted the first systematic bathymetric and benthic sampling of the global ocean floor. Prior to this voyage, prevailing geological theory posited that pelagic sediments were uniformly composed of terrigenous muds washed down from continental rivers. However, Thomson’s team discovered distinct zonation in deep-sea deposits that correlated directly with oceanic depth rather than proximity to landmasses. In abyssal zones shallower than 4,500 meters, the seabed was predominantly covered by calcareous ooze, composed primarily of the calcium carbonate skeletons of planktonic organisms such as foraminifera. Surprisingly, at depths exceeding 4,500 meters, calcareous ooze abruptly yielded to fine-grained red clay, largely devoid of organic calcium carbonate. Thomson initially hypothesized that deep-sea currents swept carbonate shells away from deeper basins. However, oceanographer John Murray subsequently demonstrated that the change in sediment composition resulted from oceanic chemical dissolution. Murray established that deep seawater, under immense hydrostatic pressure and enriched with dissolved carbon dioxide, becomes chemically aggressive toward calcium carbonate. As tests of planktonic organisms sink past the calcite compensation depth (CCD), they dissolve entirely before reaching the seafloor. Consequently, only insoluble volcanic ash, windborne dust, and metallic oxides accumulate at extreme abyssal depths, forming the characteristic red clay. Murray’s identification of the CCD fundamentally altered marine geology by proving that oceanic chemistry, rather than physical current transport, governs the spatial distribution of pelagic sediments.

According to the passage, John Murray attributed the absence of calcareous ooze at ocean depths below 4,500 meters to which of the following factors?