One of the key areas and periods for dinosaur evolution is considered to be Early
Cretaceous East Asia, of which paleoclimate, that affected dinosaur diversity, needs
to be accurately estimated. This study reconstructed paleoenvironmental information
from two paleosol sections of the Lower Cretaceous Tetori Group in Hokuriku prov-
ince, Japan. Elemental and isotopic compositions indicate that the two sections
(Sections K5 and T1) formed under similar mean annual temperature (MAT) and mean
annual precipitation (MAP) but exhibit significantly different paleosol colors (red in
the Section K5, and gray in the Section T1) and mineralogy of carbonate nodules
(dolomite–siderite in the Section K5, and dolomite–calcite in the Section T1). In addi-
tion, the oxygen isotopic ratio of carbonate minerals in the Section K5 was signifi-
cantly low. The differences in sedimentary features and isotopic composition were
considered to reflect the differences of seasonal climatic factors (e.g., monsoon) and
local settings (e.g., drainage condition) despite the two sections exhibiting similar
MAT and MAP. The results of this study suggest that the northeastern margin of East
Asia, where the Tetori Group was deposited, had temperate and humid climate with
monsoonal contrast in humidity during Aptian to Albian.
