Situated in Amnam-dong area of west Busan, Songdo Peninsula attracts more and more visitors these days with its trail built from Songdo Beach to Amnam Park. Through the trail can be observed continuous changes in lithofacies from the upper to the lower part of Dadaepo Formation and diverse volcanic rocks which intrude into and cover the formation. Also available is the view of a scenic coast along with the strata of the Cretaceous in which dinosaurs thrived. The Dadaepo Formation in the Songdo Peninsula geosite, comprises various sedimentary rocks such as conglomerates, sandstones, siltstones, mudstones, and tuffaceous sedimentary rocks. A continuous observation of changes in lithofacies from the upper to the lower part of the formation corroborates a transition in its depositional environment from fluvial to lacustrine sedimentation. Also found are diverse sedimentary structures such as bedding, cross-bedding, erosion and filling, and ripple marks as well as geologically noteworthy records like calcareous palaeosolic soil and calcrete. Reddish beds in the lower part of the formation contain fossils of dinosaur skeletons and egg nests along with trace fossils. *trace fossils: trace of an animal, e.g. shellfish’s burrow in unsolidified sedimentary deposits. A high content of chert fragments in a conglomerate bed plays a vital role in studying a paleogeographic reconstruction of the Korean Peninsula and Japan during the end of the Cretaceous. Also observed are normal faults, clastic dikes, andesitic dikes and sills, and rhyolitic dikes. In particular, a number of groups of rhyolitic dikes show a systematic direction of an east-west striking; they have been formed in rocks of peculiar shapes by the effect of differential erosion on the sedimentary country rock. Near the entrance of a trail are observed basalts or basaltic andesitic lava flows covering the upper part of the formation whereas between the upper and the lower part are distributed desitic ignimbrites. Such volcanic rocks have a significant academic value in studying the sedimentation time of the Dadaepo Formation and history of the volcanism in Gyeongsang Basin. What’s more in the peninsula are an outdoor exhibition hall for rocks and minerals, Amnam Park, Eco Park, Songdo Beach, pebble beach, Busan Sea Observatory, sea cliffs, sea caves and a geotrail path which allows visitors to explore all these attractions. * Dadaepo Formation : sedimentary sequences formed during the Cretaceous, is the oldest strata in Busan. It was during the Cretaceous when the development of Gyeongsang Supergroup was in progress; the Gyeongsang Province and the vicinities were a huge lake back then. For about 70 million years from 135 to 65 million years ago, the Gyeongsang Supergroup deposited in horizontal layers in a river basin. The Dadaepo Formation is strata formed during the middle stage of Gyeongsang Basin development. Near the end of the Cretaceous, underlying strata of lakes or rivers changed to land and volcanic ashes and later lava accumulated over the strata due to granite intrusion and violent volcanic activities.