Abstract
The Early Palaeozoic Franklinian basin of North Greenland was initiated in early Cambrian times with the onset of siliciclastic and mixed carbonate shelf deposition on a substratum of Proterozoic sediments and Precambrian crystalline basement. The basin rapidly differentiated into shelf, slope, and trough environments. The boundary between these major depositional regimes follows major roughly east-west trending lineaments. The inner-outer shelf transition fluetuated widely in position and was controlled by the interplay between sea-level changes and periodic northwards downwarping. In Ordovician-Silurian times the margin of the carbonate platform migrated northwards to coincide with the shelf-slope break and had a steep scarp configuration with an abrupt transition to the shales and turbidites of the deep-water basin. In this paper we pay special attention to the initial basin sequence (Skagen Group), the collapsed and broken platform carbonates of the Lower Cambrian Portfjeld Formation, the Middle - Late Cambrian inner-outer shelf transition and to the nature of the Silurian platform margin scarp.
Highlights
It has been known for a long time that the Early Palaeozoic basin of North Greenland contains marine deposits of both shallow and deep-water origin
We studied or re-examined localities critical for the understanding of the inner-to-outer shelf transition, the shelf-slope break, and the stages in evolution of the deep-water trough described by Surlyk et al (1980) and Surlyk & Hurst (1983, 1984)
The four-fold subdivision presented for the upper Lower Cambrian - Lower Silurian outer shelf to slope deposits af the coastal region of central and western North Greenland by Higgins & Soper (1985) was examined
Summary
In northem Wulff Land formation 2 is followed by up to 120 m of heterolithic siltstone and fine sandstone, laminated siltstone, and black sandy dolomite which constitute formation 3 This clearly indicates a shift to more quiet depositional conditions than formation 2. In northem Wulff Land the fine-grained siliciclastic deposits of formation 3 give way to dark crag-forming dolomites of formation 4 This highly characteristic facies consists of dark-grey, massive dolomite with abundant irregular cracks, veins, and vugs filled with white dolomite spar Some beds display the same type of cracks and veins filled with white dolomitic spar as seen in formation 4 This facies was probably deposited adjacent to (south of?) a stable carbonate platform represented by the basal Portfjeld Formation at depths above storm-wave base. The carbonate material was swept away from the platform during strong storm
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