The top part of Kebobutak Formation are intensely bioturbated by a Cruziana-type assemblage. The formation is interpreted to be air-fall deposits reworked in a shallow marine sublittoral setting. Above the Kebobutak Formation lies at least of dacitic pumice, volcanic lithic and crystal-rich tuffs and breccias assigned to the Semilir Formation. In East Java the base of the Semilir Formation can be identified by the abrupt termination of bioturbated reworked deposits characteristic of the Kebobutak Formation. The volcanic rocks of the Semilir Formation are characterised by features typical of terrestrial air-fall, pyroclastic surge and flow deposits including dune and antidune structures, crystal layering, well-sorted granular laminations, diffuse bedding, breccias (with metre-scale pumice blocks), thick mantling ashes, and abundant fragments of charcoal. Locally there are water-laid deposits, with scoured irregular bases, flame, traction and suspension structures, and large slump folds indicating an unstable marine slope. Smyth et al. (2011) interpret these observations to indicate the Semilir Formation was erupted in a subaerial setting in which pyroclastic flows travelled across vegetated slopes picking up and baking plant fragments, with some of these flows entering the sea. Some of the primary material would have been redeposited as lahars in distal settings. Overlying the Semilir Formation is a thick sequence of massive, resistant, monomict andesitic volcanic breccias, crystal-rich sandstones and minor lava flows of the Nglanggran Formation. The breccia beds are thick and can be mapped for several kilometres. Interbedded crystal-rich sand- stones are much thinner. The breccias are both clast- and matrix-supported with angular fragments commonly across with some blocks up to . Fragment imbrication within the breccias records diverging west and southwest flow from a source in the northeast part of the Batu Agung Escarpment. There is no evidence of any marine influence, and we interpret the Nglanggran Formation as terrestrial deposits formed by sector or repeated dome collapse, marking the end of arc activity in the Southern Mountains. The top and base of the Nglanggran Formation forms topographic breaks in slope, because the andesitic breccias are much more resistant than the underlying and overlying units, and the feature and the formation can be easily mapped across the area over a distance of .