Prof. Dr.Sean Gallen2026-07-212026-07-21https://dspace.academy.edu.ly/handle/123456789/2452These facies were deposited in three depositional environments: lobe-fringe area, medial inter-lobe area, and distal inter-lobe area. The presence of both high-energy indicators, such as clay clasts, sharp erosional bases, scours, and fragmented fishbones, as well as the occurrence of sediments reflecting suspension deposition, indicates that the lobe-fringe environment was undergoing successive shifts from high to low energy conditions. Moving farther away from the lobe, sediments show overall moderate energy conditions reflected in normal grading and some erosional contact; nevertheless, moderate and low-energy conditions alternated. Furthest away from the lobe are the distal inter-lobe sediments that show tranquil sediment deposition with only minor moderate energy deposition reflected in sharp facies contacts, and some siltstone grains in facies 3. The presence of only one type of fecal string, in these sediments, and the little bioturbated nature of inter-lobe strata suggests that the environment had been likely dysoxic and stressed but was not entirely anoxic.Lobe-fringe deposits and interlobe strata are rarely described in sedimentary systems and often neglected in descriptions of delta successions, which mostly focus on delta top, delta front, and prodelta sediments. This may partly be the case because these deposits consist mostly of mudstones, which are generally neglected in all sedimentary systems except for black shales. Here, we describe nine siliciclastic facies of predominantly mudstones from the Cretaceous Skull Creek Formation of northern Colorado, USA.PROCESSES IN MUDSTONE INTER-LOBE DEPOSITS