Microbial lumps have been found in the Maozhuang Stage(Cambrian Series 2) in the Liangcheng section,Shandong Province,China.Their macro-and micro-scale features distinguish them from other carbonate particles such as intraclasts and oncoids.Most lumps have a coarse sand to pebble size.They were mostly rounded during sedimentation or combined to form irregular shapes.A distinct boundary is present between the lumps and the surrounding cement of sparry calcite.The lumps contain either no core at all or several irregular "cores",without a distinct inner texture.They are composed mainly of calcified(micritized) microbes,most likely cyanobacteria.The microbes drilled holes in carbonate grains,after which lumps formed by micritization,cementation,and agglutination by an extracellular polymeric substance(EPS) in a high-energy shallow-marine,subtidal environment.As the lumps are directly related to microbes,they should be considered as microbialites.
Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks might be critical to the formation of limestone conglomerates.According to detailed field measurement and laboratory analyses (thin section observation and XRD analysis),four types of ribbon rocks are classified,i.e.,limestone and marlstone couplet (L-M),limestone and shale couplet (L-S),thin-bedded lime mudstone (Ltb),and laminated limestone and marlstone couplet (Cl).These ribbon rocks were mostly deposited in low-energy subtidal environments (below fair-weather wave base).Ribbon rocks exhibit various subtle deformation structures such as intrastratal cracks and "boudin" structures.Differential cementation of carbonate and argillaceous layers during early diagenesis is a prerequisite condition for the deformation of ribbon rock under compaction.Ribbon rocks would be deformed into limestone conglomerates under differential compaction that might be triggered by external forces such as storm and earthquake.
The provenance of the lower Es2 in the Shanghe area was determined from an approach incorporating analysis, elemental ratios,paleocurrent direction,the typomorphic characteristics of detritus and the distribution of conglomerate and gritstone in the peripheral basin.Typical elemental ratios characteristic of the sedimentary area were compared with those from the source areas as abstracted from sediments of the Huimin sag using cluster analysis.The results show that the distribution pattern focuses on Mg/Mn,Fe/K,Al/Na,Ba/Mn and Al/Mg.Mg/Mn is the highest ratio,from 25 to 45.This is similar to the pattern from the Precambrian.Furthermore,paleocurrent direction was used to determine provenance by examining the distribution of gritstone and the seismic progradational reflections.The research results indicate that the provenance is to the northwest in the Precambrian strata where the sand grain size is rough.To the east there is siltstone,fine sandstone and mudstone.This is significant for the exploration of oil and gas within the study area.
