Distinctive Properties of Turbiditic and Hemipelagic Mud Layers in the Algero-Balearic Basin, Western Mediterranean Sea

摘要

Two types of mud layers alternate in dominantly muddy cores of the southern Balearic Basin. Type A muds (a few cm to over 50 cm thick), macroscopically homogeneous, occur above turbidite sands or silt laminae. Type B muds (imperceptible to about 50 cm thick), comparatively coarse due to interspersed microskeletons, occur below turbidite sands or silt laminae, and lie above type A muds. The two types are distinguished in Xradiographs on the basis of texture and sedimentary structures. Type A and B mud layers in six cores were sampled at 1 to 8 cm intervals. Type A muds are distribution graded (upward shift of the entire size distribution to finer sizes), continuing the upward grading of the underlying sand turbidites. A granulometric change occurs at the boundary with type B muds which contain sand (to 16 percent), largely tests of forams and pteropod shells. The sand fraction of type A muds (