To understand the sedimentary development of the Boso Forearc Basin, central Japan, since ~ 3 Ma, we investigated paleothermal structure and consolidation trends in the central and eastern parts of the forearc basin through vitrinite reflectance measurements and consolidation tests. Vitrinite reflectance (R_m) was in the range 0.33 % to 0.61 % for the Miura Group in the central part of the forearc basin and 0.34 % to 0.41 % for the Miura and Kazusa Groups in the eastern. These values suggest a roughly uniform vitrinite reflectance for the Miura Group from the central to eastern parts. No significant vitrinite reflectance difference is observed across the ~ 3 Ma Kurotaki Unconformity in the eastern part of the basin. The consolidation yield stress (p_c) was calculated as 27.5 MPa and 32.2 MPa for the Kiyosumi and Amatsu Formations of the Miura Group in the eastern part, respectively. Both the p_c values are consistent quantitatively with represent the trend of the maximum overburden pressure estimated from the thickness and density of overlying sediments, and the difference in p_c is expected by the maximum burial depths of the strata at the sampling localities. Values of p_c in the eastern part of the basin increase with thickness of overlying sediment, showing no break across the Kurotaki Unconformity. Considering the eroded thickness of the Miura Group, the continuous trends in vitrinite reflectance and consolidation between the Miura and Kazusa Groups in the eastern part reflect the greater deposition of the eastern part of the Boso Forearc Basin since ~ 2.3 Ma.

中文翻译：

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日本中部Boso半岛中部和东部中新世后中前盆地的玻璃体反射率和固结特征：对盆地沉降的影响

为了了解日本中部Boso前臂盆地自3 Ma以来的沉积发育，我们通过镜质体反射率测量和固结测试研究了前臂盆地中部和东部的古热结构和固结趋势。前臂盆地中部的三浦集团的玻璃体反射率（R _m）在0.33％至0.61％的范围内，东部的Miura和Kazusa组的玻璃体反射率在0.33％至0.61％的范围内。这些值表明三浦集团从中部到东部的镜质体反射率大致均匀。在盆地东部〜3 Ma Kurotaki不整合面中未观察到明显的镜质体反射率差异。固结屈服应力（p _c东部地区三浦组的清澄组和天松组的）计算值分别为27.5 MPa和32.2 MPa。这两个p _c值在定量上都与从上覆沉积物的厚度和密度估算出的最大上覆压力的趋势一致，并且p _c的差异是由采样地点的地层的最大埋藏深度所预期的。p _c的值盆地东部的沉积物随上覆沉积物厚度的增加而增加，表明黑崎不整合面没有破裂。考虑到三浦群的厚度被侵蚀，东部的三浦群和风间群的镜质体反射率和固结的连续趋势反映了自约2.3 Ma以来Boso前臂盆地东部的更大沉积。