The sedimentary rocks (Jikunsan Formation) in this site were formed in the early Paleozoic Ordovician times (ca. 460 million years ago) and consist dominantly of dark gray to black shale. They yield well-preserved and diverse invertebrate fossils including trilobites (a group of arthropods), brachiopods, graptolites (literally translated as "written on stone"), and cephalopods (squids are the modern representative). Exoskeletons of most specimens are dissolved away, thus leaving internal and external molds. Fossilsf range in size from less than 1cm to 22cm. Similar fossil assemblages have been documented from China, Australia, South America, North America, and even Europe, which provides invaluable information to study the geologic age and paleoenviroments of the Korean peninsula during the early Paleozoic times

Rocks exposed at the Gumunso area are composed of carbonates deposited in the early Paleozoic Ordovician Period(490-440 million years ago) The Gumunso is a small pond formed by combined erosional processes of rivers and underground waters, and shows typical documents often described it as the Cheon Stream(Literally means hole-river) and it has been known as the fountainhead of the Nakdonggang, the second longest river in Korea. There are also a number of legends relating to the Gumunso. The carbonate rocks of the Gumunso area (Makgol Formation) preserve a variety of sedimentary structures, such as mud cracks, ripple marks, stromatolites, bird-eye stucture, burrows and halite pseudomorphs. The overlying Jikunsan Formation yields diverse fossils of Ordovician age : They include trilobites, brachipods, cephalopds, and graptolites among others. These rocks and fossils are invaluable material for reconstructing the early Paleozoic sedimentary enviroments of the Korean peninsula