Channelized systems in mixed carbonate-siliciclastic settings are challenging to characterize from the geological standpoint as facies variability is expected to be high (e.g., siliciclastic porous channel fills, carbonate cemented channel fills or even carbonate channel fills). Determining the lithological composition is crucial for not only understanding the basin evolution but also is required for drilling plans either if the channels serve as reservoirs or drilling hazards. An example of one such compositionally mixed channel system is identified in the San Andres and Grayburg formations in the Midland Basin, TX. For this specific example, channels are presumably siliciclastic infilled while the shelf the channels cut across is dominantly carbonate. An integrated study of core, well-log, and seismic data is conducted to analyze the facies variability of the channelized interval and understand its geomorphological evolution. Seismic attributes such as coherent energy, sweetness and spectral components (CWT) prove to be the most efficient at enhancing the contrast between the clastic vs carbonate elements; demonstrating that it is feasible to depict the lithological heterogeneity between the channel infills and the shelf at a seismic scale. Additionally, conventional seismic interpretation and geometric attributes (e.g., apparent dip, dip azimuth and magnitude, etc.) suggests two categories of channel incisions: type I, characterized by V-shaped bases, straight and mostly oriented in a NE-SW direction; and a type II, that tend to be U-shaped, slightly sinuous, and oriented in a NW-SE trend. Well-log based litho-density techniques such as ρmaa-Umaa and core descriptions support the seismic observations by illustrating the vertical and horizontal heterogeneity and how the channel infills are dominantly siliciclastic in nature. A 3D lithology model constrained to the previous analyses illustrates a dominance of siliciclastics in the Lower San Andres while the Upper San Andres and Grayburg are limestone-rich with episodic siliciclastic events (i.e., related to the channel incisions) and dolostone (in the Upper Grayburg). Lithologies and morphological changes are directly related to changes in the sea level and source rock composition. This study is pioneering in its understanding of the siliciclastic deposition in the middle Guadalupian units in this portion of the Midland Basin, which are referred in literature as the Midland sands and identified as analogs of the Brushy and Cherry Canyon formations in the Delaware Basin.