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Matsugadaira Motai Metamorphic Complex Formation

Matsugadaira Motai Metamorphic Complex Fm

Period:

Cambrian

Age Interval:

Cambrian (Guzhangian), (8a)

Province:
South Kitakami Belt-Okago region

Type Locality and Naming

Nagasaka-Soma district

Synonym:

Lithology and Thickness

These metamorphic outcrops comprise amphibolites (basalt and gabbro origin), greenschist, pelitic schist and serpentinized ultrabasic rocks, with subordinate amounts of siliceous and psammitic schists.

[Figure 1: Stratigraphy of the Palaeozoic of the South Kitakatmi Belt, NE Japan (after M. Ehiro et al., 2016)]

Lithology Pattern:

Basement

Relationships and Distribution

Lower contact

Regionally, the schematic strat column indicates this is the oldest unit.

Upper contact

The Matsugadaira Unit is unconformably overlain by the Upper Devonian Ainosawa Fm (Ehiro & Okami 1990). Sasaki et a1., (1997) reported an unconformity outcrop between Motai ultrabasic rocks and covering middle Palaeozoic sediments of the Tobigamori Fm (see

figure) at Natsuyama. Regionally, the schematic strat column indicates the next younger unit as Shoboji Diorite Fm

Regional extent

Nagasaka-Soma district

GeoJSON

null

Fossils

Age

Finally, K—Ar hornblende metamorphic ages of c. 500 Ma have been obtained from banded amphibolites (Kanisawa et a1., 1992), indicating the basement racks to be at least Cambrian in age.

Age Span:

Beginning stage:

Guzhangian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

500.50

Ending stage:

Jiangshanian

Fraction up in the ending stage:

1.0

Ending date (Ma):

491.00

Depositional setting

Depositional pattern:

Additional Information

Compiler:

Moreno, T., WALLIS, S., Kojima, T. & Gibbons, W. (Eds) 2016. The Geology of Japan. Geological Society. London. 1-24.