Corals: The unusual occurrence of hermatypic corals in the sediments in the southern part of Boso Peninsula has attracted the attention of investigators for over 100 years. Naumann (1877) was the first to investigate the coral-rich sediments near Numa, which he believed to be of Tertiary age. Yabe and Sugiyama (1932, 1935) examined the deposits as a part of their study of corals in Japan. They listed 46 species of corals from sediments near Numa and Koyatsu villages and suggested that they are of Holocene age. They also reported occurrence of 7 species of reef-building corals in the present Tateyama Bay. Subsequent C¹⁴ datings of corals from the Numa bed (Hoshino, 1967; Konishi, 1967) confirmed the Holocene age of the sediments.

Hamada (1963) found additional 29 species of coral in Koyatsu, and Eguchi and Mori (1973) discovered two more coral species in Koyatsu, bringing the total to 77 species. Hamada (1963), on the basis of comparison with similar coral fauna in Tanabe Bay (Kii Peninsula), argued that the corals in Koyatsu lived in depths of about 10 m.

Molluscs: Yokoyama (1911) reported the occurrence of several tropical species of molluscs and later (1924), described 124 species of molluscs from the coral-bearing deposits and estimated their age as Pleistocene. Nomura's study (1932) of molluscs from the Boso and Miura Peninsulas included also the coral-bearing deposits of the southern Boso, which he regarded as of Holocene age. He suggested that the molluscan fauna indicates a slightly warmer climate than that of the present Boso Peninsula, being perhaps as warm but not warmer than the present sea off Kii Peninsula in southwest Japan. Matsushima (1979), in a study of southern Kanto postglacial molluscan assemblages (which included the southern Boso Peninsula), pointed out the appearance of tropical species Ostrea paulwiae and Tellimimactra edentula during the peak of the postglacial transgression about 6,500 to 6,000 yr B.P. He explained their disappearance around 4,000 yr B.P. by a change of sedimentary environment rather than a lowering of temperature.

Foraminifers: The microfauna of the Numa coral bed was investigated by Asano (1936), who failed to find species characteristic of coral reefs in tropical regions, such as Amphistegina radiata, Operculina venosa, etc., and concluded that the climate at the time of deposition was not markedly different from the present one.

Marine terraces: Naruse and Sugimura (1953) briefly described the Holocene sediments exposed along the Tomoe River. Yoshikawa and Saito (1954) investigated the Holocene terraces and the bathymetry of the shallow sea near Chikura on the west coast. Sugimura and Naruse (1954, 1955) studied the distribution of marine terraces in the southern Kanto region and pointed out the correlation between the elevation of terraces and the amount of uplift during historical earthquakes. Yonekura (1975) further studied the relationship between uplift (as indicated by terrace distribution) and tectonic movements. Yokota (1978) investigated the distribution of terraces and described the sediments forming them. along the southeast coast of the southern Boso Peninsula. Nakata et al. (1980) reexamined in detail the distribution of marine terraces in the Boso Peninsula south of the 35° N parallel and emphasized crustal movements as the main cause of relative sea level changes in the area.