1991 Fiscal Year Final Research Report Summary
Pacific Neogene Events in Japan and South America
| Project/Area Number |
02044062
|
|---|
| Research Category |
Grant-in-Aid for international Scientific Research
|
| Allocation Type | Single-year Grants |
|---|
| Section | Joint Research |
|---|
| Research Institution | Shizuoka University |
|---|
Principal Investigator |
TSUCHI R. Professor, Fac. Sci., Shizuoka University, 理学部, 教授 (60021929)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ALDANA M. Chief Geologist, IN GEMMET, Lima, Peru, 主任研究員
VILLAVICENCIO-R. E. Chief of Paleontology, IN GEMMET, Lima, Peru, 古生物学研究室, 室長
MARTINEZ-P. R. Professor, Fac. Sci., University of Chile , Chile, 理学部, 教授
IBARAKI M. Research Assistant, Fac. Sci., Shizuoka University, 理学部, 助手 (30109128)
KOIZUMI I. Professor, Fac. Sci., Hokkaido University, 理学部, 教授 (20029721)
|
|---|
| Project Period (FY) |
1990 – 1991
|
| Keywords | Neogene / Geologic event / Peru / Chile / Accelerated evolution / Climatic optimum / Seawater temperature / Bioseries / Mollusca |
|---|
| Research Abstract |
This is an international research on the elucidation of timing and nature of Neogene geologic events in Japan and on the Pacific coast South America which has been carried out through two years of 1990 and 1991 in collaboration of the Japanese research group with geoscientists of Peru and Chile. Based upon careful examinations of our collected samples from the Neogene sequences in Peru and Chile since 1985, scientific results were obtained as follows :
The mid-Neogene maximum of the surface seawater temperature during the earliest Middle Miocene time around 16 Ma will be one of the most pronounced events in the Pacific, which is considered to be the climatic maximum of the Neogene. During the interval, a tropical marine fauna migrated into North Japan (42^ON). This warm event seems to have culminated at about 16 Ma based on rich occurrences of the tropical elements especially in the N8b age. In the Southeast Pacific, Middle Miocene and later sequences of Peru are predominated by biosili
… More
ceous sediments due to a coastal upwelling of the Peruvian cold current. However, the Camana Formation in southern Peru, consisting of calcareous sandstone with larger foraminifera and indicating a tropical condition, is assignable to Zone N8b at about 16 Ma. The maximum southward expansion of tropical larger foraminifera in Australia is another strong evidence in the South Pacific. The Mid-Neogene climatic optimum thus seems to be synchronous in the circum-Pacific region.
Another prominent event will be an accelerated biotic evolution clearly recognized in middle latitude areas during the latest Neogene. In Japan, an endemic molluscan bioseries of Suchium suchiense-giganteum has demonstrated accelerated evolutions in shell form in every 0.3 m. y. since 3 Ma. In northern Chile, a bioseries of Turritella cingulatiformis-cingulata also exhibits accelerated evolutionary changes in shell form in every 0.7 m. y. since 3 Ma. The accelerated evolution thus may be a notable biotic event in middle latitude areas owing to a flexible climatic changes in these areas. Less
|
