The South Polar Layered Deposits (SPLD) are composed of alternating layers of ice and dust in varying proportions. The accumulation of the layers is driven by orbital forcings, and the cadence and structure of these layers preserve a record of the past martian climate. We use SHARAD data to examine the radar properties of SPLD reflectors and to infer their spatial correlations. Crossing orbit tracks are incoherently stacked to improve the echo signal-to-noise ratio and extend the delineation of reflectors, laterally and vertically, into areas where they are not evident in individual SHARAD traces. Three distinct radar reflection "facies" are identified: (1) shallow layers that are generally well-focused in processed radargrams, (2) less densely spaced layers that occur over much of the depth of the SPLD but are blurred to varying degrees, and (3) low reflectivity zones. A pattern of diffuse echoes termed "fog", which originates from an uncertain surface or volume scattering mechanism, extends to varying round-trip delay times and is often correlated with blurring of subsurface reflections. The fog signature is pervasive, being present in some form over 64% of the SPLD. Unconformities are observed in stacks of reflectors that both intersect the surface and are confined to the subsurface. Only one major deviation from near-horizontality of the reflectors, located to the east of Australe Mensa, was identified. There is no evidence for major unconformities that suggest multiple depositional centers that later merged into the SPLD. Instead, SHARAD data suggest that the materials of the SPLD were deposited regionally, superposing materials from previous depositional episodes.
