Paleomagnetic measurements were conducted on 96 ariented loess specimens collected from the Lochuan section in Shanxi Prov., the total thickness of which is up to 130 m and more. The results have provided evidence tha...Paleomagnetic measurements were conducted on 96 ariented loess specimens collected from the Lochuan section in Shanxi Prov., the total thickness of which is up to 130 m and more. The results have provided evidence that the deposition of Late Pleistocene Malan Loess and Middle Pleistocene Lishih Loess in the Lochuan section took place during the Brunhes normal epoch. The lower limit of the Lishih Loess which represents the boundary between the Brunhes epoch and the Matuyama epoch is located at the top of the lower silt bed, corresponding to a depth of 75 m. The Wucheng Loess, which recorded the Jalomillo normal polarity event, deposited during the middle-late period of the Matuyama reversed epoch. The upper limit of the Jalamillo is set at a depth of 100 m. and the lower limit at 110 m. Experiments have shown that rotated remanent magnetization of the specimen resulted from AF demagnetization Can be effectively eliminated by means of magnetic cleaning in opposite directions,despite of the differences in magnetic stability and ages of various strata (loess, silt bed, buried soil and weathered beds) in the Lochuan section.展开更多
One hundred and seventeen oriented specimens of loess (in the form of cube with edges of 4 cm) were collected from the W ueheng section in Hsihsien County, Shansi Province, China. After magnetic cleaning in an a.c. fi...One hundred and seventeen oriented specimens of loess (in the form of cube with edges of 4 cm) were collected from the W ueheng section in Hsihsien County, Shansi Province, China. After magnetic cleaning in an a.c. field, remanent magnetization of the specimens was measured with an astatie magnetometer (sensitivity 4×10^-8 units CGSM). The normal magnetozone of Brunhes normal epoch is recorded in Upper Pleistocene Malan Loess and Middle Pleistocene Lishih Loess which contains typical Choukoutien fauna. The reversed magnetozane of Matuyama reversed epoch is observed in Lower Pleistocene Wucheng Loess, within Which Villafranchian Nihowan fauna is known to occur.展开更多
Palaeomagnetie measurement on 254.samples. from the 600 m-long drill core Bo-3(118°30'E， 39°15'N) clearly reveals the epoches of Gauss normal polarity, Matuyama reversed polarity and Brunhes normal ...Palaeomagnetie measurement on 254.samples. from the 600 m-long drill core Bo-3(118°30'E， 39°15'N) clearly reveals the epoches of Gauss normal polarity, Matuyama reversed polarity and Brunhes normal polarity and several important polarity events,such as Kaena. olduvai and Jaramillo et.al since 300my ago.On the basis of polnrity,boundary ages and the corresponding thickness an average sedimentation rate is estimated to be 19.5cm per 1000years which is in agreement with data in other areas in the North China Plain.Micro-palaeobiologic fossils indicate three marine beds to a depth of 80m that can be compared with the western coast of Bohai Bay,suggesting three raphic divission of the drill core has also been discussed.The base of Holocene is at a depth of 15m(0.01-0.012my B.P.),Late Pleistocene at 46m(0.11-0.13my B.P.0Middle Pleistocene 171m(0.73my B.P.)and the Quarternary bottom can be defined prcliminarily at 490m(2.48my B.P.)or 587m(about 3my B.P.).展开更多
Paleomagnetic measurements were carried out on 134 vertically oriented spccimens taken from a Cenozoic drilling core in the Hengshui area, North China Plain.An alternating magnetic field with a peak value of 160 Oe, w...Paleomagnetic measurements were carried out on 134 vertically oriented spccimens taken from a Cenozoic drilling core in the Hengshui area, North China Plain.An alternating magnetic field with a peak value of 160 Oe, was adopted for oppositedirection-magnetic cleaning to eliminate secondary viscous and rotated remanent magnetization. The results proved greatly successful. It is evident from the paleomagnetic studies that geomagnetic polarity epochs and events were recorded in this set of loose sediments during the last 3 m.y. with the boundary between the Brunhes normal epoch and the Matuyama reversed epoch (ca. 0.7m.y.) at a depth of 140m and the Matuyama-Gauss boundary (ca. 2.43m.y.) at 489 m depth with respect to the drilling cores. At present, it is acceptable that the beginning of the Quarternary should be dated back at 1.8--2 m.y., rightly corresponding to the basal limit of the Olduvia event at the depth of 360m. The area is characterized by a high and constant rate of sedimentation (ca. 200mm per 1,000 years).展开更多
The Maoming Basin is one amongst a group of Cretaceous-Teniary basins in South China. 347 samples were collected from drill cores MR and MB and sechon MS (110°54’E, 21°45 ’N). Most of the lithological unit...The Maoming Basin is one amongst a group of Cretaceous-Teniary basins in South China. 347 samples were collected from drill cores MR and MB and sechon MS (110°54’E, 21°45 ’N). Most of the lithological units are of Tertiary age. The cores include the Laohuling, Shangcun,Huangniuling and Youganwo formations . The MR core (874m in length) has recorded the polarity history from Normal Zone 18 to Normal Zone 11 on the Geomagnetic Polarity Time Scale (GPTS).The strata were formed from about 42Ma to 32Ma, that is from Late Eocene to Early Oligocene.A mean sedimentation rate of this stratigraphic column is 8.1 cm/ka.展开更多
Over 800 paleomagnetic samples were collected from 79 sample localities, ranging inage from Devonian, Carboniferous, Permian to Jurassic for palcolatitude research on theGulzhou terrain. The area sampled covers 13 cou...Over 800 paleomagnetic samples were collected from 79 sample localities, ranging inage from Devonian, Carboniferous, Permian to Jurassic for palcolatitude research on theGulzhou terrain. The area sampled covers 13 counties with an area of about 50000 km2. Thepaleomagnetic results obtainal indicate that the Guizhou was at 11. 4°S in Devonian, 4. 5° -9. 3°S in Carboniferous, 2. 6°- 4. 5°S in Permian, 14. 8°N in Triassic and 24. 5°- 26. 0°N inJurassic. In the Cretaceous period, the paleo-latitude of the area was at 22. 4 - 23. 6°N.Therefore, a variation curve of paleo-latitude is established in this paper for the Guizhou terrainfrom Late Devonian to Late Cretaceous time.展开更多
文摘Paleomagnetic measurements were conducted on 96 ariented loess specimens collected from the Lochuan section in Shanxi Prov., the total thickness of which is up to 130 m and more. The results have provided evidence that the deposition of Late Pleistocene Malan Loess and Middle Pleistocene Lishih Loess in the Lochuan section took place during the Brunhes normal epoch. The lower limit of the Lishih Loess which represents the boundary between the Brunhes epoch and the Matuyama epoch is located at the top of the lower silt bed, corresponding to a depth of 75 m. The Wucheng Loess, which recorded the Jalomillo normal polarity event, deposited during the middle-late period of the Matuyama reversed epoch. The upper limit of the Jalamillo is set at a depth of 100 m. and the lower limit at 110 m. Experiments have shown that rotated remanent magnetization of the specimen resulted from AF demagnetization Can be effectively eliminated by means of magnetic cleaning in opposite directions,despite of the differences in magnetic stability and ages of various strata (loess, silt bed, buried soil and weathered beds) in the Lochuan section.
文摘One hundred and seventeen oriented specimens of loess (in the form of cube with edges of 4 cm) were collected from the W ueheng section in Hsihsien County, Shansi Province, China. After magnetic cleaning in an a.c. field, remanent magnetization of the specimens was measured with an astatie magnetometer (sensitivity 4×10^-8 units CGSM). The normal magnetozone of Brunhes normal epoch is recorded in Upper Pleistocene Malan Loess and Middle Pleistocene Lishih Loess which contains typical Choukoutien fauna. The reversed magnetozane of Matuyama reversed epoch is observed in Lower Pleistocene Wucheng Loess, within Which Villafranchian Nihowan fauna is known to occur.
文摘Palaeomagnetie measurement on 254.samples. from the 600 m-long drill core Bo-3(118°30'E， 39°15'N) clearly reveals the epoches of Gauss normal polarity, Matuyama reversed polarity and Brunhes normal polarity and several important polarity events,such as Kaena. olduvai and Jaramillo et.al since 300my ago.On the basis of polnrity,boundary ages and the corresponding thickness an average sedimentation rate is estimated to be 19.5cm per 1000years which is in agreement with data in other areas in the North China Plain.Micro-palaeobiologic fossils indicate three marine beds to a depth of 80m that can be compared with the western coast of Bohai Bay,suggesting three raphic divission of the drill core has also been discussed.The base of Holocene is at a depth of 15m(0.01-0.012my B.P.),Late Pleistocene at 46m(0.11-0.13my B.P.0Middle Pleistocene 171m(0.73my B.P.)and the Quarternary bottom can be defined prcliminarily at 490m(2.48my B.P.)or 587m(about 3my B.P.).
文摘Paleomagnetic measurements were carried out on 134 vertically oriented spccimens taken from a Cenozoic drilling core in the Hengshui area, North China Plain.An alternating magnetic field with a peak value of 160 Oe, was adopted for oppositedirection-magnetic cleaning to eliminate secondary viscous and rotated remanent magnetization. The results proved greatly successful. It is evident from the paleomagnetic studies that geomagnetic polarity epochs and events were recorded in this set of loose sediments during the last 3 m.y. with the boundary between the Brunhes normal epoch and the Matuyama reversed epoch (ca. 0.7m.y.) at a depth of 140m and the Matuyama-Gauss boundary (ca. 2.43m.y.) at 489 m depth with respect to the drilling cores. At present, it is acceptable that the beginning of the Quarternary should be dated back at 1.8--2 m.y., rightly corresponding to the basal limit of the Olduvia event at the depth of 360m. The area is characterized by a high and constant rate of sedimentation (ca. 200mm per 1,000 years).
文摘The Maoming Basin is one amongst a group of Cretaceous-Teniary basins in South China. 347 samples were collected from drill cores MR and MB and sechon MS (110°54’E, 21°45 ’N). Most of the lithological units are of Tertiary age. The cores include the Laohuling, Shangcun,Huangniuling and Youganwo formations . The MR core (874m in length) has recorded the polarity history from Normal Zone 18 to Normal Zone 11 on the Geomagnetic Polarity Time Scale (GPTS).The strata were formed from about 42Ma to 32Ma, that is from Late Eocene to Early Oligocene.A mean sedimentation rate of this stratigraphic column is 8.1 cm/ka.
文摘Over 800 paleomagnetic samples were collected from 79 sample localities, ranging inage from Devonian, Carboniferous, Permian to Jurassic for palcolatitude research on theGulzhou terrain. The area sampled covers 13 counties with an area of about 50000 km2. Thepaleomagnetic results obtainal indicate that the Guizhou was at 11. 4°S in Devonian, 4. 5° -9. 3°S in Carboniferous, 2. 6°- 4. 5°S in Permian, 14. 8°N in Triassic and 24. 5°- 26. 0°N inJurassic. In the Cretaceous period, the paleo-latitude of the area was at 22. 4 - 23. 6°N.Therefore, a variation curve of paleo-latitude is established in this paper for the Guizhou terrainfrom Late Devonian to Late Cretaceous time.
