紀伊半島中央部に分布する四万十帯白亜系の構造的最上位の地層である麦谷層について，岩相分布，地質構造，および砕屑性ジルコンU-Pb年代を明らかにした．本地域の麦谷層は，構造的上位から下位へ，泥岩，破断した砂岩泥岩互層，および混在岩を主とする伊豆尾ユニットと，泥岩を主とする狭戸ユニットに区分され，層理面は概ね西北西-東南東走向で，北に中角で傾斜する．麦谷層の3試料から得られた砕屑性ジルコンU-Pb年代によると，最も若いジルコン粒子年代もしくは最も若いクラスター年代は100～110Maを示し，後期白亜紀以降の年代を示すジルコンは1粒子も認められなかった．後期白亜紀に西南日本では活発な火成活動が生じていたことを考慮すると，麦谷層の堆積年代はアルビアン～セノマニアンであると推定される．麦谷層の最も若いジルコン粒子年代，最も若いクラスター年代，および年代構成は，アルビアン～セノマニアンに堆積した湯川層のジルコン年代の特徴とも一致する．

球状炭酸塩コンクリーションは，世界各地の様々な地質時代の海成層から普遍的に産するが，その形成過程はいまだ完全には理解されていない．本研究では，愛知県知多半島の先端部に分布する中新統師崎層群下部豊浜累層中にみられる長径約1.5mの巨大ドロマイト質コンクリーションについて，その形成過程を明らかにすることを目的に，堆積学的および地球化学的な種々の観察・分析を行った．その結果，埋没深度数百mに達するまでのごく初期続成過程においてメートルサイズの巨大なコンクリーションが形成することが示された．その形成時間は数十年と見積もられ，これまで考えられていた巨大炭酸塩コンクリーションの形成速度よりもはるかに速いものである．

岐阜県飛騨地方の高根地域に分布する安山岩質平行岩脈群と斑れい岩について地質と岩石磁気・古地磁気を調査した．前期中新世の安山岩質岩脈群からは「新しい岩脈法」によって2つの正断層型応力状態が推定された．安山岩の主要な強磁性鉱物は磁鉄鉱で，いくつかの岩脈には磁硫鉄鉱も含まれる．磁鉄鉱が担う磁化方位は東偏する．その方位は岩石磁気学的に高い信頼性を有するが，傾動の評価が難しい．方位の東偏は時計回り回転または北西への傾動を想定することで説明でき，前者の可能性が高い．この地域では岩脈群形成後に北中国地塊に対して約45°の時計回り回転が起こり，これは日本海拡大に関連した西南日本の時計回り回転を示すに違いない．高根と東海地方，北陸地方の間では大きな相対回転が起こっていない．伊豆弧衝突による回転の影響は高根までは及んでいないようだ．岩脈群形成時の応力状態は地磁気永年変化を平均化できるほどの期間継続していたと考えられる．

The Neogene Chikura Group, which is widely exposed in the southeastern part of Minamiboso City, Chiba Prefecture, Japan, is made up of a thick sequence of marine sedimentary rocks deposited in a middle to upper bathyal environment. The group comprises (in ascending order) the Shirahama, Shiramazu, Mera and Hata formations. The upper Pliocene Shirahama Formation is composed mainly of red-brown volcaniclastic sandstone and the Nojimazaki Conglomerate Member. This member comprises volcaniclastic conglomerate with granules to boulders of basalt and andesite, and is characterized by pebbles of andesite, basalt, granodiorite, gabbro, sandstone, siltstone, greenish tuff, and chert. We obtained Anisian and Ladinian (Middle Triassic) radiolarians from chert pebbles, and Bajocian to Callovian (Middle Jurassic) radiolarians from a siliceous siltstone pebble. These Mesozoic pebbles were probably derived from a Mesozoic accretionary complex (present-day Kanto District) in the northwestern part of Boso Peninsula.

A Middle Jurassic-earliest Cretaceous accretionary complex crops out in the North Kitakami Belt, located in the Kitakami Massif, Northeast Japan. The Kadoma Complex, which is distributed along the southwestern margin of the belt, contains felsic tuff with radiolarian fossils (Triassocampe? spp.) of possible Middle-Late Triassic age according to the previous work. Therefore, there is a possibility that the Kadoma Complex includes a Triassic accretionary complex.

In this study, the U-Pb ages of zircon grains from tuffaceous mudstone near the outcrop of the radiolarian-fossil-bearing felsic tuff were obtained to establish the depositional age of the Kadoma Complex. The youngest cluster of zircon grains yielded a peak age (weighted mean) of 209.4±3.7 Ma. Therefore, the tuffaceous mudstone is considered to have been deposited in the Late Triassic, given the age of radiolarian fossils from the nearby felsic tuff.

If the tuffaceous mudstone is a trench-fill deposit, then at least part of the Kadoma Complex represents a Late Triassic accretionary complex. This view provides insights into the Triassic accretionary complex, which is rare in the Japanese Islands, and into the tectonics of the early Mesozoic arc-trench system at the eastern Asian margin.

We report, in detail, ²¹⁰Pb and ¹³⁷Cs profiles in three 20-cm-long multi-cores from seafloor sediments that were collected using a remotely operated vehicle from shelf slopes at water depths of less than 1000 m off Sanriku, NE Japan. We detected ¹³⁷Cs at 8 cm below the seafloor in the three samples. The sedimentation rates with burial compaction were calculated at 0.045-0.354 g cm^-2 y^-1 on the basis of the ²¹⁰Pb concentrations in the three samples.

The Setul Group, which contains a thick Lower Ordovician to Early Devonian limestone succession, occurs in northwestern Perlis State and the Langkawi Islands, Peninsular Malaysia. We report a lowermost Devonian conodont fauna characterized by Flajsella stygia and Flajsella streptostygia from a limestone section near the small town of Kaki Bukit, in what was previously considered to be Ordovician limestone. The studied limestone corresponds to the youngest part of the Mempelam Limestone. Nine species of conodonts in six genera are systematically investigated herein, of which three species Dvorakia amsdeni, D. philipi and F. streptostygia are the first reports in the Peninsula Malaysia. The stratigraphic correlations of the rock are also briefly discussed.