Objective The Jilin-Liaoning area has widely spread Meso- and Neoproterozoic sediments and is always a focused area for researching Precambrian geology. Previous study has achieved a series of results about Neoprotero...Objective The Jilin-Liaoning area has widely spread Meso- and Neoproterozoic sediments and is always a focused area for researching Precambrian geology. Previous study has achieved a series of results about Neoproterozoic stratigraphy in this area, but the lack of precise geochronological data and signs of stratigraphic correlation has resulted in the long controversial stratigraphic age and regional correlation. During recent years,展开更多
For more than a century, molar tooth structure （MTS） has been studied. The study developed in three stages. During the first stage （before 1980）, researchers described three basic morphologies of MTS, mainly from ...For more than a century, molar tooth structure （MTS） has been studied. The study developed in three stages. During the first stage （before 1980）, researchers described three basic morphologies of MTS, mainly from the Belt Supergroup in North America, and they provided several hypotheses for the origin of MTS. During the second stage （1980-1999）, the frequent discoveries of MTS on all continents resulted in many detailed descriptions of their shape and in several hypotheses concerning the origin of MTS. Notably, hypotheses of MTS＇s origin such as seismic activity and biological activity were developed. Since 2000, research has progressed into a new stage （the third stage）. This is due to discoveries of MTS in the Me- so-Neoproterozoic of China and elsewhere, and the ongoing debate on the seismic or biologi- cal origin is replaced by a hypothesis that involves gas expansion and chemically-controlled carbonate precipitation （both of them possibly affected by biological activities）. This latter idea has gradually been commonly recognized as the mainstream theory. Despite continued disa- greements, researchers now agree that microsparry calcite played a controlling role regarding the development and the global distribution of MTS in time and space during the Proterozoic, the morphological diversity, and the impact on the sedimentary environment. The present con- tribution analyses the three major hypotheses regarding the origin of MTS; it also discusses the shortcomings of the hypotheses regarding a seismic or biologic origin, and it details the modern hypothesis that links formation of cracks to the precipitation of sparry calcite. It is de- duced that important questions dealing with the Precambrian can be answered, among other aspects regarding the depositional palaeogeography and stratigraphic correlations.展开更多
Molar tooth(briefly called MT)carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure.According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autocht...Molar tooth(briefly called MT)carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure.According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autochthonous and allochthonous,and each type can be further divided into a series of subtypes.The autochthonous MT can be divided into filamentous(MF1),ribbon,nodular and dotted type(MF4),in which the ribbon one can be subdivided into simple vertical(MF2)and complex ribbon(MF3),broken ribbon by storm in situ(MF5)and MT within nodular limestone(MF6).Allochthonous MT includes conglomerate clasts and horizontal detritus.Studying on the links between MT and the host rocks on five stratigraphic sections in the southeastern Jilin and eastern Liaoning indicates that the morphology of MT is closely related to host rocks,and seven genetic types by relationships between MT and the host rocks with facies interpretations are classified and discussed in this paper.The sedimentary environments of MT formation will be diverse if their morphologies are different.展开更多
基金supported by the Nature Science Foundation of China(grant No.41472082)China Geological Survey(grant No.121201102000150012)
文摘Objective The Jilin-Liaoning area has widely spread Meso- and Neoproterozoic sediments and is always a focused area for researching Precambrian geology. Previous study has achieved a series of results about Neoproterozoic stratigraphy in this area, but the lack of precise geochronological data and signs of stratigraphic correlation has resulted in the long controversial stratigraphic age and regional correlation. During recent years,
基金sponsored by the National Natural Science Foundation of China (40772078,41472082)
文摘For more than a century, molar tooth structure （MTS） has been studied. The study developed in three stages. During the first stage （before 1980）, researchers described three basic morphologies of MTS, mainly from the Belt Supergroup in North America, and they provided several hypotheses for the origin of MTS. During the second stage （1980-1999）, the frequent discoveries of MTS on all continents resulted in many detailed descriptions of their shape and in several hypotheses concerning the origin of MTS. Notably, hypotheses of MTS＇s origin such as seismic activity and biological activity were developed. Since 2000, research has progressed into a new stage （the third stage）. This is due to discoveries of MTS in the Me- so-Neoproterozoic of China and elsewhere, and the ongoing debate on the seismic or biologi- cal origin is replaced by a hypothesis that involves gas expansion and chemically-controlled carbonate precipitation （both of them possibly affected by biological activities）. This latter idea has gradually been commonly recognized as the mainstream theory. Despite continued disa- greements, researchers now agree that microsparry calcite played a controlling role regarding the development and the global distribution of MTS in time and space during the Proterozoic, the morphological diversity, and the impact on the sedimentary environment. The present con- tribution analyses the three major hypotheses regarding the origin of MTS; it also discusses the shortcomings of the hypotheses regarding a seismic or biologic origin, and it details the modern hypothesis that links formation of cracks to the precipitation of sparry calcite. It is de- duced that important questions dealing with the Precambrian can be answered, among other aspects regarding the depositional palaeogeography and stratigraphic correlations.
基金Supported by the National Natural Scientific Foundation of China (Grant No. 40772078)International Geological Correlation Program (IGCP447), (Grant No. SC/GEO/546/447)+1 种基金Foundation of Geology Iustitute, CAGS (Grant No. J0903)Natural Scientific Development Foundation of Yangtze University (Grant No. 2007ZP005)
文摘Molar tooth(briefly called MT)carbonate is one of the Proterozoic carbonates with enigmatic sedimentary structure.According to the morphology of MT,it can be divided into two main genesis-morphology types,i.e.,autochthonous and allochthonous,and each type can be further divided into a series of subtypes.The autochthonous MT can be divided into filamentous(MF1),ribbon,nodular and dotted type(MF4),in which the ribbon one can be subdivided into simple vertical(MF2)and complex ribbon(MF3),broken ribbon by storm in situ(MF5)and MT within nodular limestone(MF6).Allochthonous MT includes conglomerate clasts and horizontal detritus.Studying on the links between MT and the host rocks on five stratigraphic sections in the southeastern Jilin and eastern Liaoning indicates that the morphology of MT is closely related to host rocks,and seven genetic types by relationships between MT and the host rocks with facies interpretations are classified and discussed in this paper.The sedimentary environments of MT formation will be diverse if their morphologies are different.
