This paper describes vertical fine-scale geochemical heterogeneity of Estonian graptolite argillite (GA). GA samples from Pakri and Saka outcrop sections were collected at 20 cm intervals for chemical analysis of major and trace elements, including rare earth elements. The study indicates GA enrichment in U, V, Mo and Pb with respect to the average black shales and thus confirms the formerly reported data on GA geochemistry in general. However, the content of enriched elements and other trace metals was recorded to vary greatly across the sequences suggesting that trace metal distribution in GA is notably more heterogeneous than previously assumed. The origin of the observed complex distribution of trace elements was likely controlled by the interplay of different primary metal supply-sequestration factors/processes, such as synsedimentary redox-driven sequestration of redox sensitive elements, the provenance of clastic input, the postsedimentary redistribution, etc.

The occurrence of Cambrian to Ordovician organic-rich black shale deposits has been known in Baltoscandia, including Estonia, for a long time. The Estonian graptolite argillite (GA) shows high to very high concentrations of U (800 ppm), Mo (1000 ppm), V (1600 ppm), Ni and other heavy metals, and are rich in N, S and O, unlike normal shale. The present study provides a new estimate of the total GA tonnage in Estonia, including estimates for U, Zn and Mo. The total preserved volume of GA is about 31.92 billion m 3 , while about 9.02 billion m 3 has been eroded between the Estonian mainland and western islands. The total mass of GA is about 67 billion tonnes at a specific gravity of 2.1 g/cm 3 . About 18.93 billion tonnes of GA has been eroded and re-deposited, including 1.8 million tonnes of U, 22.7 million tonnes of Zn, 6.6 million tonnes of Pb, 4.4 million tonnes of Mo and 13.3 million tonnes of V. In Estonian GA the total U 3 O 8 reaches 6.7 million tonnes, ZnO 20.6 million tonnes and MoO 3 19.1 million tonnes as calculated using a cell size of 400 m.

This article presents a centimetre-to micrometre-scale study of sedimentary fabrics from Lower Ordovician metalliferous black shale from the Baltic palaeobasin. Two sections of the Türisalu Fm. NW and NE Estonia were analysed with light microscopy and scanning electron microscopy. This rock unit is characterised by mostly thin bedding (,10 mm), common occurrence of minor erosional features, and a large variety of sedimentary fabrics, including graded, cross-laminated and massive fabrics. Based on this, we suggest that dynamic sedimentation events, rather than commonly assumed slow net sedimentation, may be the dominant mechanism behind the accumulation of these beds. The storm-related near-bottom flows and the bed-load transport of mud particles were likely common distribution agents of organic-rich mud. The mud (re)distribution, mainly via near-bottom flows and controlled by flat seafloor topography and general clastic starvation, might explain the present lateral distribution and diachronous character of the Türisalu Fm. Documented traces of microbial mat growth and siliceous sponges in the NW Estonia indicate that in more sheltered settings, biogenic factors played a vital role in developing primary mud characteristics. The geochemical palaeoredox proxies, and high trace metal and organic matter content suggest that mud sedimentation could occur under anoxic conditions. The observed sedimentary fabrics and traces of bioturbation, however, favour prevailing oscillating redox conditions in the lower water column. The recorded heterogeneity of microfabrics indicates that dynamic transport and intermittent deposition together with biogenic factors likely forced the development of an array of unique (bio)geochemical microenvironments for syngenetic trace element sequestration.

The concession area of the Jordan Oil Shale Energy Co (JOSE) is located in the southern border zone of the Attarat Um Ghudran deposit, next to the Wadi Maghara deposit, both consisting of marinite type oil shale (OS). These deposits of the Upper Cretaceous to Lower Paleogene Muwaqqar Chalk-Marl Formation form a huge north-southward elongated oil shale basin in Central Jordan, with resources over 55 billion tons. JOSE has drilled a regular grid of boreholes with a full coring of the up to 90 m thick OS seam and its lower and upper contact layers. Visually, the OS unit is a rather homogenous dark-colored (grey, black, brownish grey) succession of finely bedded (laminated) kerogen-bearing carbonate rocks that has been in earlier papers described as a uniform lithological unit. The aim of the geological and lithological studies of the JOSE exploration area was (i) to investigate the vertical variation of OS composition and, if present, to define layers within the OS unit, and (ii) to identify lithological varieties and chemical composition of OS present in different layers.On the basis of field evidence, downhole gamma-logging, chemical analyses and other criteria, an original detailed scheme of the layered structure of oil shale and barren rocks was introduced. A total of eight OS layers (indexed as A, B1, B2, C, D, E1, E2, E3) and at least four barren dolomitic limestone interlayers were distinguished. The present publication is dedicated to the chemical study of the layers and the total OS seam. A representative gapless collection of 632 conventional core samples from 12 cores serves as the base for the comparative study of the layers. Two main (SiO 2 , CaO) and two subordinate chemical (Al 2 O 3 and P 2 O 5 ) components of the mineral matter (MM), and loss on ignition (LOI 500 °C) approximately reflecting the content of organic matter (OM), are the basic variables discussed. Contents of SiO 2 and CaO always show negative correlation, 19whereas local enrichment with Al 2 O 3 and P 2 O 5 occurs in certain interbeds. OM content in samples has no strong correlation with mineral matter abundances. The eight distinguished OS layers comprise both those strongly enriched in CaO, or oppositely in SiO 2 . The layers differ in rate of internal heterogeneity reflected in variation of standard deviation values. With rare exceptions, the barren limestone interlayers are dolomitized, strongly enriched with MgO and depleted of CaO. The database on the distribution of mineral compounds and trace elements serves for the 3-D block modelling of the deposit composition. However, further data analysis is required for the understanding of lateral changes of the layers' mineral composition, and geological and geochemical structure.

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