The Geochemical Feature' s Comparison between the Typical Rhythmic Bedding Iimestone and Marl of Upper Jurassic Malm in Southern Germany

Key words: 
• southern Germany /
• limestone and marl /
• geochemical feature

Abstract: The ty pical rhy thmic bedding limestone and marl of upper Jurassic M alm in southern Germany were d4posited in typical epicontinental platfo rm envirnment. The rocks in the sectio n were bed by bed sampled, their residues were obtained by isolation with monochlo acid (CH₂ClOO H). The mineral assemblage in residues m ainaly consists of quartz, K-feldspar and clay minerals according to X-ray diffraction analy sis. The analy sis of residues bo th in mineral assemblage and in chemical composition show s that the non-carbo nate m a-terials in limestone and in marl are no essential difference. The geochemical analy sis with XRFS (X -ray Fluo-rescence Spectrometry) w as taken both on rocks and on the residues. SiO₂, Al₂O₃, Fe₂O₃, K₂O and TiO₂ are related to detritus, and demonstrate the same relationships in limestone and in marl, moreover, they all have a g ood positive relationship to the residues content and are classified to the so-called detritus elements group. They rem ained in the sediments and had no change after deposition. Their different concentrations in lime-stonse and in marl are only due to the effect of carbonate sediments, dilution during deposition. The elements Sr, Zn, Mn, and Mg are controlled by diagenesis. They exist fi rstly in the carbonate form, but change much in the period of diagenesis. Dolomitization in some posme posi tion of the section leads to high Mg-content in the rocks. These elements are classified to the group of diagenesis elements. The elements in this g roup have no clear relationship to the residues-contents. However, the behavio r of elements such as S, Ba, Rb and P is be-tween the two groups of elements. They were controlled partly by the detritus and partly by the diagenesis, and they are somerelationship to the residues-contents. The fo rmation of rhy thmic bedding limes tone and marl is the result result of the variation of carbo nate sedimentation rat and then compressed w ith pressure solution. But the differences of them are only in residues content but not essentially in the mineral assemblage and geo-chemical composition of non-carbo nate material in the rocks.