Cretaceous Of Hokkaido Research Articles

A Second Specimen of the Crossognathiform Fish Apsopelix miyazakii from the Cretaceous Yezo Group of Mikasa Area, Central Hokkaido, Japan

The specimen collected from the Cretaceous Yezo Group of Mikasa area, central Hokkaido, Japan by T. Matsumoto and T. Omori in 1955, deposited in the University Museum, the University of Tokyo is determined as a second specimen of Apsopelix miyazakii, which is the crossognathid fish described from Teshionakagawa area, northern part of Hokkaido in 2012. Some characters unconfirmed in the holotype, including the dorsoventrally long opercle and subopercle; the well-preserved preopercle having many radial openings of the sensory canal; the sensory canal of the second infraorbital bone having many branches; the presence of the forth infraorbital bone; the large supracleithrum; and the scale-like postcleithrum are preserved in the second specimen. An estimated standard length of the second specimen is more than about 10 cm larger than that of the holotype. The emended diagnosis is proposed for A. miyazakii based on the holotype and the second specimen. The discovery of the second specimen extends the range of A. miyazakii throughout the Upper Turonian. Also, Apsopelix miyazakii possibly lived in a shelf environment near the open ocean.

Santonian-Campanian neoselachian faunas of the Upper Cretaceous Yezo Group in Nakagawa Town, Hokkaido, Japan

Fifty-one fossil shark teeth, including Hexanchiformes, Echinorhiniformes, Squaliformes and Lamniformes, are described from two localities in Nishichirashinai and Omagari formations of the Yezo Group in Nakagawa Town, Hokkaido, Japan. They include the first occurrence of Protosqualus from the northwestern Pacific and suggest the onset of the adaptation to deep-water environments of the Squaliformes in this region by early Campanian. Different sedimentary settings of the two localities may have caused different taxonomic compositions. The co-existence of Hexanchiformes and Lamniformes is also known in a contemporaneous Japanese fauna and those of southern high latitudes and suggests effects of paleogeographic settings on the global distribution of Upper Cretaceous neoselachian taxa.

Allometry between Suture Line Length and Phragmocone Volume in Some Cretaceous Ammonoids

The allometric relationship between suture line length and phragmocone volume was examined in 28 specimens belonging to six ammonoid species recovered from the Upper Cretaceous Yezo Group of Hokkaido, Japan. The suture perimeter was calculated by summing the distances between digitized points along the suture line in a photograph. The phragmocone volume was calculated using a modified Raup's model. The relationship between suture perimeter and phragmocone volume in each species was expressed as an allometric equation on a logarithmic scale. The exponent of ontogenetic allometry estimated for each species ranged from 0.462 to 0.626. The exponents estimated were much greater than the exponent in the case of isometry (0.333) and the value previously obtained through interspecific comparison. Calculation using a theoretical morphologic model indicates that allometric exponents for the suture perimeter of approximately 0.5 reflect positive allometry of the septal surface area with respect to body size. The present results suggest that strong positive allometry of the suture perimeter leads to a considerable positive allometry of the septal surface area resulting in satisfying Kleiber's scaling law, although its functional significance remains unclear.

上部白亜系蝦夷層群の Cenomanian/Turonian 境界付近の有機炭素の安定同位体比スパイク(白亜紀〜古第三紀のバイオイベント : 海洋生物の変遷と消長)

上部白亜系蝦夷層群の Cenomanian/Turonian 境界付近の有機炭素の安定同位体比スパイク(白亜紀〜古第三紀のバイオイベント : 海洋生物の変遷と消長)

Paleoenvironmental study and integrated stratigraphy of planktic and benthic foraminifera and radiolaria of the Cretaceous Yezo Group

Paleoenvironmental study and integrated stratigraphy of planktic and benthic foraminifera and radiolaria of the Cretaceous Yezo Group

Redescription of the first pterosaur remains from Japan: the largest flying reptile from Asia

Pterosaur remains are found in numerous deposits of the world, but most are isolated and fragmentary elements. This is the case of Japan where a small number of specimens from those volant reptiles have been reported. Here, we redescribe the first pterosaur remains from Japan (NSM PV15005) that were found in outcrops of the Upper Cretaceous Yezo Group (Santonian–lower Campanian) in the Mikasa area of Hokkaido. Further preparation of this material revealed several pterosaur bones, including the distal end of a left femur, a non-ungual phalanx and a proximal caudal vertebra. Based on the double-condyle articulation of the caudal element and the main features of the femur, this specimen is referred to a pteranodontid-like pterosaur. Its wingspan is estimated to be around 6.8 m, making it the largest pterosaur recorded not only from Japan, but also from Asia so far, indicating that large flying reptiles were widespread worldwide during the Upper Cretaceous.

Correlation of the tuff beds in the Cretaceous Yezo Group in Hokkaido

Correlation of the tuff beds in the Cretaceous Yezo Group in Hokkaido

Megafossil biostratigraphy and carbon isotope stratigraphy of the Upper Cretaceous Yezo Group in the Obira area, Hokkaido, Japan

Megafossil biostratigraphy and carbon isotope stratigraphy of the Upper Cretaceous Yezo Group in the Obira area, Hokkaido, Japan

A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan

Abstract Hayakawa, T., Hirano, H. 2013. A revised inoceramid biozonation for the Upper Cretaceous based on high-resolution carbon isotope stratigraphy in northwestern Hokkaido, Japan. Acta Geologica Polonica, 63 (2), 239-263. Warszawa. Biostratigraphic correlations of inoceramid bivalves between the North Pacific and Euramerican provinces have been difficult because the inoceramid biostratigraphy of the Japanese strata has been based on endemic species of the northwest Pacific. In this study, carbon stable isotope fluctuations of terrestrial organic matter are assembled for the Upper Cretaceous Yezo Group in the Haboro and Obira areas, Hokkaido, Japan, in order to revise the chronology of the inoceramid biozonation in Japan. The carbon isotope curves are correlated with those of marine carbonates in English and German sections with the aid of age-diagnostic taxa. According to the correlations of the carbon isotope curves, 11 isotope events are recognised in the sections studied. As a result of these correlations, the chronology of the inoceramid biozones of the Northwest Pacific has been considerably revised. The revised inoceramid biozones suggest that the timing of the origination and extinction of the inoceramids in the North Pacific biotic province is different from the stage/substage boundaries defined by inoceramids, as used in Europe and North America.

Carbon isotope stratigraphy of terrestrial organic matter for the Turonian (Upper Cretaceous) in northern Japan: Implications for ocean-atmosphere 13C trends during the mid-Cretaceous climatic optimum

Carbon isotope data of terrestrial organic matter (δ 13 C TOM ) obtained in Hokkaido, northern Japan, from the marine Cretaceous Yezo Group along the northwestern Pacific margin elucidated a detailed chemostratigraphy for the Turonian Stage in this region of East Asia. Chemostratigraphic intra-basin correlation reveals three positive δ 13 C TOM events in the Middle–Upper Turonian of the Yezo Group. δ 13 C TOM fluctuations in these events show similar patterns in the Yezo Group, indicating that terrestrial organic matter is mixed sufficiently before deposition in the Yezo Basin. These δ 13 C TOM events are correlated with previously documented δ 13 C carbonate events in Europe (the Lulworth–Round Down, Glynde–Pewsey, and Late Turonian Events) based on global biostratigraphy. Our chemostratigraphic correlations strengthen the use of these δ 13 C events for global correlation of the Turonian marine successions. In addition, global correlation of Turonian marine and terrestrial δ 13 C events identifies changes in isotopic difference between δ 13 C TOM and δ 13 C carbonate (Δ TOM-carbonate ), which are interpreted to reflect changes in atmospheric p CO 2 levels, and climate-driven stresses of humidity and soil processes. In earlier stages of Turonian, Δ TOM-carbonate values are increased. Elevated atmospheric p CO 2 , and increased humidity and soil processes in enhanced greenhouse conditions during mid-Turonian, are interpreted to enlarge Δ TOM-carbonate values. In later stages of Turonian, Δ TOM-carbonate values are at a constant level, and the lowering of atmospheric p CO 2 or decrease of climate stress related to the diverse paleoclimatic cooling is interpreted to have restored the ocean-atmosphere δ 13 C trends.

Stratigraphic correlation between the shallow marine and hemipelagic sequences based on the integrated stratigraphy of planktic foraminifera, carbon isotope and tuff of the Cretaceous Yezo Group.

Stratigraphic correlation between the shallow marine and hemipelagic sequences based on the integrated stratigraphy of planktic foraminifera, carbon isotope and tuff of the Cretaceous Yezo Group.

Erratum : Megafossil biostratigraphy of the Upper Cretaceous Yezo Group in the northern Hobetsu area, Hokkaido, Japan

地質学雑誌，第117巻11号に掲載された本田ほか（p.599-616）の論説の謝辞において読者に誤解を与えかねない表現がありましたのでお詫びして，以下を削除致します．著者一同p.614左段43行から46行目「特に，西村智弘博士には，Takashima et al.（2010）が示したイノセラムス化石帯の時代の詳細な議論を参考程度に留めるご助言を頂き，本論文の改善につながった．」

Chemical composition of the detrital heavy mineral in the Upper Cretaceous Yezo Group in the Teshio-Nakagawa area, northern Hokkaido, Japan

Chemical composition of the detrital heavy mineral in the Upper Cretaceous Yezo Group in the Teshio-Nakagawa area, northern Hokkaido, Japan

Megafossil biostratigraphy of the Upper Cretaceous Yezo Group in the northern Hobetsu area, Hokkaido, Japan

Megafossil biostratigraphy of the Upper Cretaceous Yezo Group in the northern Hobetsu area, Hokkaido, Japan

Taxonomic Evaluation of Various Morphological Characters in the Late Cretaceous Desmoceratine Polyphyletic Genus “Damesites” from the Yezo Group in Hokkaido and Sakhalin

Intra- and interspecific variation and ontogenetic changes in various shell characters of the Late Cretaceous desmoceratine ammonoid “Damesites” are described, and their taxonomic implications are discussed based on specimens from the Cretaceous Yezo Group in Hokkaido and Sakhalin. Our study reveals that many “diagnostic” features (e. g., appearance of longitudinal striations, height of ribbing, regularity of ribbing as well as constriction curvature) and early internal shell structures, are in fact inappropriate as diagnostic features of “Damesites” morphotypes. In contrast, ontogenetic changes in shell ornament, curvature of growth lines and whorl expansion ratio are herein demonstrated to be key characters for species recognition and reconstructing the phylogenetic relationships of the taxa of the subfamily Desmoceratinae. Based on these results, previously described “Damesites” species from the uppermost Turonian-lower Campanian interval should be reclassified into three groups. “Damesites damesi,” “D. damesi intermedius,” “D. semicostatus,” and “D. laticarinatus” are assigned to the first group. “D. ainuanus” and “Damesites sp.” are assigned to the second group. “D. sugata” from the Yezo Group represents the third group. Furthermore, analysis of ontogenetic changes in shell ornament, curvature of growth lines, and whorl expansion ratio suggests that the second and third groups together belong to a different evolutionary lineage from the first group.

A new Turonian (Late Cretaceous) species of <i>Inoceramus</i> (Bivalvia) from the Yezo Supergroup, Hokkaido, northern Japan

A new inoceramid species (Inoceramus nakagawensis sp. nov.) from the Upper Cretaceous Yezo Supergroup, Hokkaido, Japan, is reported and systematically described in detail. The shell sculpture of I. nakagawensis sp. nov. is characterized by very fine, distinct, and regular to somewhat irregular concentric rings. Its occurrence is probably restricted to the upper Lower to lower Middle Turonian, making it a short-ranging species. The present species would be closely allied to Inoceramus cuvieri Sowerby, 1814, from the middle to upper Turonian Stage of Far East Russia.

A large latitudinal displacement of a part of Cretaceous forearc basin in Hokkaido, Japan: paleomagnetism of the Yezo Supergroup in the Urakawa area

Paleo-and rock magnetic experiments were carried out on the Cretaceous Yezo Supergroup in the Urakawa area (southern central Hokkaido) in order to detect tectonic episodes of the ancient eastern Eurasian margin. Characteristic remanent magnetization determined for five sites resides in magnetite, and has primary origin as indicated by positive result of tilting test. Bedding-parallel fabric of anisotropy of magnetic susceptibility and anisotropic acquisition of isothermal remanent magnetization (IRM) indicate significant inclination shallowing after deposition and lock-in of remanence. Shallowing ranges from 4° to 11° for the five sites on the basis of IRM anisotropy. The flattening-corrected mean inclination is still anomalously shallow (31°). Considering the correlation between the obtained inclination data and the geomagnetic polarity Chron C33r−C32r, a block containing the Urakawa area was located at a low latitude (16.7°N) during Campanian and then has experienced at largest 3400 km northward transportation. Transcurrent fault motions along the continental margin may be responsible for the transportation, as inferred from extremely large rotational motion (−161°). The Cretaceous Yezo forearc basin contains an exotic landmass that had evolved along a remote continental margin, then been transported as a result of oblique subduction.

Tectonic implications of paleomagnetic data from upper Cretaceous sediments in the Oyubari area, central Hokkaido, Japan

Abstract Paleomagnetic studies provide constraints on the geometric configuration of the eastern Eurasian margin on geological time scales. Characteristic remanent magnetization components were isolated from eight sites by progressive demagnetization executed on samples from 25 sites in the Oyubari area, central Hokkaido where the Late Cretaceous Yezo Group is distributed. After tilt‐correction, all sites show normal polarity site‐mean directions, and well‐clustered directions pass a positive fold test and a correlation test. Planktonic foraminifera indicate an age range of Cenomanian to Turonian, and the studied section is correlated to the geomagnetic polarity chron C34n. Reliable formation‐mean directions that have been corrected for post‐depositional shallowing (D = 7.5°, I = 65.9°, α95 = 6.6°) are characterized by inclination data indicative of no significant latitudinal translation since the Late Cretaceous. Central Hokkaido has, therefore, been situated adjacent to easternmost Mongolia including Sikhote Alin around the present latitude since the Late Cretaceous. Declination data require significant differential rotation between Hokkaido and the eastern Asian margin, which may be indicative of rearrangement of crustal blocks along the continental margin.

Two ammonite species of the genus Sharpeiceras from the Cretaceous of Hokkaido (studies of cretaceous ammonites from Hokkaido and Sakhalin-LXXXI)

Two ammonite species of the genus Sharpeiceras from the Cretaceous of Hokkaido (studies of cretaceous ammonites from Hokkaido and Sakhalin-LXXXI)

Carbon-isotope stratigraphy and its chronostratigraphic significance for the Cretaceous Yezo Group, Kotanbetsu area, Hokkaido, Japan

Carbon-isotope stratigraphy and its chronostratigraphic significance for the Cretaceous Yezo Group, Kotanbetsu area, Hokkaido, Japan