Tectonic, sedimentary and diagenetic controls on sediment maturity of lower Cambrian quartz arenite from southwestern Baltica

Abstract

Lower Cambrian quartz arenitic deposits have a worldwide occurrence. In this study, petrographic and mineralogical analyses were carried out on samples from the quartz‐rich Ringsaker Member of the Vangsås Formation from southern Norway and the corresponding Hardeberga Formation from southern Sweden and on the Danish island of Bornholm. The quartz arenite is almost completely quartz cemented and has an average intergranular volume of 30%. The quartz cement is the dominating cause for porosity loss. Dissolution along stylolites and microstylolites is suggested to be the primary and secondary source for the quartz cement respectively. The quartzose sandstone from southern Norway was severely cemented prior to the Caledonian Orogeny, thus limiting the tectonic influence on diagenesis during thrusting. For most samples, authigenic clay minerals and detrital phyllosilicates represent ca. 5% of the present‐day composition. This, together with a low feldspar content, of on average 4%, indicates that the sediment was extremely quartz‐rich already during deposition. The low amount of feldspar prior to burial and the formation of early diagenetic kaolinite point to weathering, sediment reworking and early diagenesis act as important controls on sediment maturity. The large variation in clay‐mineral and feldspar content between the localities, as well as within the sandstone successions, can be explained by different palaeogeography on the shelf during deposition and subsequently dissimilar subjection to reworking and early diagenetic processes. Weathering in the provenance area, reworking in the depositional shallow‐marine environment and meteoric flushing during the burial stage are suggested to explain the high mineralogical maturity of the lower Cambrian sandstone from southwestern Baltica. These processes may generally account for similar quartz‐rich shallow‐marine sandstone units, deposited as a result of intensive continental denudation and during temperate to subtropical and moderately humid conditions.

Influencing Factors on Petrography Interpretations in Provenance Research—A Case-Study Review

“…The data include a sequence from the Permian to Palaeogene of Northern Europe (from Germany in the south to the Barents Sea in the north) with a transition from Permo-Triassic tectonically passive to rift-dominated continental and Jurassic to Cretaceous marine rift basins, to Palaeogene passive-margin marine environments [20,32,33,[36][37][38][39][40]. They also include coastal Cambrian passive-margin sandstone from Scandinavian Baltica [41][42][43], Silurian-Devonian intracratonic basin sandstone from the Paraná Basin in Brazil [35], Cretaceous [1] (solid black lines), and the modified versions of Dickinson et al [2] (dashed black lines) and Weltje [3] (grey lines). For the use of the discrimination fields, the Gazzi-Dickinson point-counting method should be used with a grain-matrix limit of 63 µm.…”

“…The data include a sequence from the Permian to Palaeogene of Northern Europe (from Germany in the south to the Barents Sea in the north) with a transition from Permo-Triassic tectonically passive to rift-dominated continental and Jurassic to Cretaceous marine rift basins, to Palaeogene passive-margin marine environments [20,32,33,[36][37][38][39][40]. They also include coastal Cambrian passive-margin sandstone from Scandinavian Baltica [41][42][43], Silurian-Devonian intracratonic basin sandstone from the Paraná Basin in Brazil [35], Cretaceous Alpine deposits [34,44], rift-related Iberian Cretaceous to Pyrenean Palaeogene continental to marine deposits [45,46], and recent intracontinental sand from central Spain [47]. The material represents fluvial, aeolian, lacustrine, deltaic, coastal, shallow-marine, slope, and deep-marine depositional environments.…”

“…In the data set, Arribas et al [47] and Caja et al [46] used the Gazzi-Dickinson method with separate classes for carbonate clasts and sand-sized quartz, feldspar, and mica crystals in rock fragments. Lorentzen et al [42,43] and Ärlebrand [40] used the Gazzi-Dickinson method but applied a 30 µm and 20 µm matrix cut-off, respectively. von Eynatten and Gaupp [34] and Augustsson et al [20] used a modified Gazzi-Dickinson method with all rock fragments counted as such.…”

“…As McBride [56] applied a smaller matrix cut-off (20 µm) than Garzanti [23] (63 µm), the scheme of McBride [56] possibly is most appropriate for the studies reviewed here that used grain-matrix-size limits of 20 µm or 30 µm [40,42,43]. This is because different grain sizes will produce sediment of different mineralogical compositions.…”

“…Others focus more on diagenetic processes than on provenance, thus presenting detailed information on the intergranular volume and mineralogical alterations and dissolutions, giving only fragmentary information on the framework composition (cf. the range of petrographic details, e.g., in Lorentzen et al [42,43]). A different focus alone may lead to the use of different compositional and textural categories for the petrographic results and thus different classification of the same components.…”