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The Posidonia Shale from northwest Germany displays a threefold stratigraphic subdivision: lower marlstone, middle calcareous shale with bivalve shells, and upper calcareous shale. Deposition commenced after transgression over a disconformity on the Pliensbachian. Absence of current features indicates depositional conditions below wave base. Sediment infilling to water depths coincident with wave base probably caused cessation of Posidonia Shale deposition. Calcitic carbonate, organic matter and detrital clay are principal primary components. TOC values are 2–15%. Macerals are mostly from marine phytoplankton; terrigenous macerals are minor. HI values are high (500–800). Detailed sampling reveals a thin (4.5 m) low carbon zone within the middle shale; water column oxidation and bacterial alteration may account for this facies. Clay and organic matter relationships suggest that land-derived nutrients controlled phytoplankton productivity; carbonate constituents were a diluent to organic matter accumulation. Absence of burrowing, abundance of organic matter, and pervasive diagenetic pyrite demonstrate continual anoxia below the sediment-water interface. However, C/S relationships suggest that a euxinic water layer did not extend far above the depositional surface. The occurrence of benthic bivalves in the middle shale indicates that bottomwater tolerable to epibenthos sometimes prevailed. Sulphate-reducing bacteria modified the primary organic matter causing a 20–30% loss.

__________________________________________ Introduction and acknowledgments.__________________ Geography. ________________________________________ Previous work._____________________________________ Rocks of metasedimentary origin _____________________ Marble or metalimestone________________________ Quartz-potassium feldspar and associated gneiss____ Pyroxenic gneiss._______________________________ Garnetiferoxis gneiss and amphibolite____________ Hypersthene-quartz-oligoclase gneiss______________ Biotite-quartz-feldspar and associated gneiss_-__-Epidote-scapolite-quartz gneiss and associated rocks. Miscellaneous gneiss.___________________________ Stratigraphy of metasedimentary gneiss.______________ Orthogneiss._______________________________________ Metagabbro gneiss._____________________________ Syenite gneiss._________________________________ Igneous rocks._____________________________________ Pyroxene syenite, pyroxene granite, and pyroxene alaskite series._______________________________ Petrology.._-______-__________._____ Sparta Lake belt__________________________ Ford belt.__.-_- .-______.____.___________ Holland belt.______________________________ Hyper«thene granite, _______________________ Hornblende granite and alaskite__________________ Rocks of uncertain origin-___________________________ Amphibolite_ ___________________________________ Quartz-oligoclase gneiss._________________________ Biotite-quartz-oligoclase gneiss._______________,..._ Albite alaskite________________________________ Quartz-microcline gneiss.________________________ Dikes.____________________________________________ Petrogenesis ______________________________________ Pyroxenic gneiss._______________________________ Quartz-potassium feldspar gneiss and associated epidotic gneiss._______________________________ Quartz-oligoclase rocks._________________________ Hypersthene-quartz-oligoclase gneiss__________ Quartz-oligoclase gneiss (Losee Gneiss)________ Amphibolite_ _ ________________________________ Quartz-microcline gneiss.________________________ Hornblende and pyroxene syenite orthogneiss_____ Granitic and syenitic rocks_______________________ Metamorphic facies_____________________________ Franklin block.____________________________ Beaver Lake block__________________________ Ryker Lake block_________________________ Comparison with nearby areas._______________

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