Global sea-level has changed in a cyclic manner through geologic history, but the regularities of these changes are yet to be fully understood. Despite certain （and sometimes significant） differences, the available ...Global sea-level has changed in a cyclic manner through geologic history, but the regularities of these changes are yet to be fully understood. Despite certain （and sometimes significant） differences, the available Mesozoic eustatic curves permit the outlining of long-term eustatic cycles, which are provi- sionally defined as cycles recognizable at the stage level and higher. Interpretation of the Triassic eustatic curves indicates two orders of long-term cycles and a lst-order sea-level rise throughout the entire period. The Jurassic eustatic curves imply cyclicity of one or two orders, and a 1st-order eustatic rise during the entire period is also evident. Most challenges are interpretations for the Cretaceous; two to four orders of long-term eustatic cycles can be established for this period. Generally, the hierarchy of the long-term eustatic cycles might have changed through the Mesozoic. If so, and if one considers differences of cycles of the same order between the periods of this era, it is difficult to apply ＂standard＂ hierarchical classifications to the documented cycles. The hypothetical uncertainty of the hierarchy of the Mesozoic long-term eustatic cycles is an imoortant challenge for modern researchers.展开更多
Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 ...Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.展开更多
文摘Global sea-level has changed in a cyclic manner through geologic history, but the regularities of these changes are yet to be fully understood. Despite certain （and sometimes significant） differences, the available Mesozoic eustatic curves permit the outlining of long-term eustatic cycles, which are provi- sionally defined as cycles recognizable at the stage level and higher. Interpretation of the Triassic eustatic curves indicates two orders of long-term cycles and a lst-order sea-level rise throughout the entire period. The Jurassic eustatic curves imply cyclicity of one or two orders, and a 1st-order eustatic rise during the entire period is also evident. Most challenges are interpretations for the Cretaceous; two to four orders of long-term eustatic cycles can be established for this period. Generally, the hierarchy of the long-term eustatic cycles might have changed through the Mesozoic. If so, and if one considers differences of cycles of the same order between the periods of this era, it is difficult to apply ＂standard＂ hierarchical classifications to the documented cycles. The hypothetical uncertainty of the hierarchy of the Mesozoic long-term eustatic cycles is an imoortant challenge for modern researchers.
基金This paper is an outcome of the research programof sequence stratigraphy (SSLC) supported by the Stateac~sinn of ScienCe and
文摘Depositional sequences may be distinguished into six ranks of units as giga-, mega-, meso-, ortho-, sub- and micro-sequence, and are interpreted to be formed during the eustatic cycles with time-intervals of 500-6000 Ma, 60-120 Ma, 30-40 Ma, 2-5 Ma, 0.1-0.4 Ma and 0.02-0.04 Ma respectively. All of them are thought to be essentially related to cosmological cycles, except the megasequence which may be caused by the long-term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the cosmological cycles in sedimentation.
