Fundamentals of Geology Practice Exam 2025 – Complete Study Resource

The term for a cross-stratified sand lens containing thin streaks of mud is flaser bedding. This type of bedding typically occurs in environments with fluctuating currents, such as tidal zones, where there are alternating periods of sand deposition and mud deposition. The presence of thin streaks of mud among thicker layers of sand indicates variability in the conditions during deposition, specifically highlighting periods when finer mud particles could settle out of suspension.

Flaser beds are characterized by a dominant sand matrix with intermittent muddy layers, showing a clear layering effect that results from the interplay of energy levels in the environment. This distinct appearance is what differentiates flaser bedding from other bedding types. Notably, each of the other bedding types mentioned—lenticular, graded, and ripple bedding—represents different depositional environments and characteristics, emphasizing the importance of identifying flaser bedding for sedimentology and geological studies.