The Nagara River is a 166 km-long river originated from Mt. Dainichigatake, and runs to the south along Route 156. It merges with Itadori River at the mouth of the Nobi delta, then flows into Ise Bay (Pacific Ocean) after merging with Ibi River near the mouth.
The Nagara River covers 1,709 km², and its valley is covered mainly by Jurassic to earliest-Cretaceous accretionary complex sediments of the Mino belt. The Mino belt consists mainly of sedimentary rocks (sandstone and mudstone) with minor amount of oceanic rocks such as greenstone (metamorphosed basalt), chert and limestone of older age (Carboniferous to Triassic) as blocks or thin layers. Rocks in an accretionary complex are intensely sheared under strong stress during its formation and exhumation processes, which destroyed the original stratigraphy.
Other major lithologies are Nohi Ryolites and granitoids. The Nohi Ryolites is volcanoclastic rocks that are widely distributed in NW-SE direction covering middle-north Gifu and south Toyama Prefectures. The main constituent of the Nohi Ryolites is ryolitic welded tuff, a remelted (and recrystallised) volcanic ash by its own heat after deposition. Granitoids belong to Ryoke belt which is widely distributed in the middle to upstream of the Nagara River. Some of limestone in the Mino belt are metamorphosed by heat of granitic intrusion. These rocks contain unique metamorphic minerals that are not found in other types of rocks.

Nagaragawa River rocks

Same as the Kiso river, many cobbles in the Nagara riverbanks are derived from the Triassic to Jurassic Mino Belt. The Mino Belt is an accretionary complex that consists mainly of sandstone and mudstone, and includes blocks of chert, limestone and greenstone.

Greenstone
Greenstone is a metamorphosed (altered) basalt that was a major constituent of oceanic crust. The original phenocrysts such as pyroxene and plagioclase are now replaced by chlorite and calcite, respectively, leaving their original grain shapes. Such a crystal grain is called a pseudomorph. The original grounmass is replaced by an aggregate of fine-grained albite (sodic plagioclase) and chlorite.

Limestone
A limestone which was formed on the seamount. The matrix is filled by nanno oods (fine-grained aphyrric carbonate), and some calcareous fossils (ooids) are also found. A horizontal vein found in the picture is an evidence of the high temperature fluid. Matrix calcium carbonate resolved into the fluid was slowly crystallised as calcite by cooling of the fluid. You may find a grain filled by relatively large calcite grains in the middle-right of the field of view. This grain might be a hollow inside the fossil that enabled large growth of calcite crystals.

Bulk sand

Quartz occupies about the half of the bulk sand, followed by K-feldspar, calcic plagioclase, albite (sodic plagioclase). Quartz and feldspars occupy the three quarter of total modal proportion. However, heavy minerals such as orthopyroxene and iron-titanium oxide also occupy a certain amount of mode. One melilite grain was also found. Melilite is characteristic to metamorphosed carbonate rocks (skarn).

Heavy Minerals

Heavy mineral composition is quite simple. The most abundant iron-titanium oxide (e.g. ilmenite) and the subordinate pyroxenes occupy most of the modal proportion.

Orthopyroxene composition (magnesium content: Mg#) has a sharp peak around Mg# 60-62, which is the same as Kisogawa river-sand. This coincides with the compositional range of the orthopyroxenes in the Ontake-1 tephra, the main tephra of the Ontake series. Other small peaks are recognised at around Mg# 58-60 and 82-84 (although the latter two has only 1 count). The former is not found in the Kisogawa-river. The latter may be the same as the Mg# 82-84 peak found in the Kisogawa river-sand. Although provenance of the tephra are not identified except for the Ontake-1, the compositional variation in Nagaragawa orthopyroxene are interpreted as a mixture of at least three different origins.

Zircon U-Pb ages
Although there are not enough analyses, the obtained zircon ages seem to be grouped into two. One group has younger ages than 100 Ma, originated from young igneous rocks of the Nohi and Okumino Ryolites. The older group (> 1500 Ma) are derived probably from sandstones of the Mino belt.