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The carbon cycle, alkalinity, and liming
Published in Richard W. Soderberg, Aquaculture Technology, 2017
Carbonate platforms are structures formed by the deposition of carbonate sediments, principally composed of the skeletons of calcarious algae. Carbonate sediments also occur in deeper waters as a result of deposition of the skeletons of amoeba-like organisms called planktonic foraminifers.
Evolution of diagenetic fluids in the deeply buried, upper Ediacaran Dengying Formation, Central Sichuan Basin, China
Published in Australian Journal of Earth Sciences, 2023
Y. J. Hu, C. F. Cai, Y. Li, R. Zhou, Y. J. Tang, J. F. Hu, F. C. Lu, P. Sun
The Sichuan Basin, located in the Yangtze Craton, southwest China, is a large intracratonic basin with an area of ∼230 000 km2 (Cai et al., 2014). This basin is divided into five sub-basins: centre, south, north, east and west (Figure 1). During the accelerated breakup of the Rodinia supercontinent in the Neoproterozoic, the Yangtze Block was subjected to rifting and then evolved into a passive continental margin by extensional tectonics in the Cambrian (Wang & Li, 2003). The upper Ediacaran Dengying Formation in the Sichuan Basin is divided into four members (I–IV) and has a total thickness of 200–900 m (Figure 2). The lowest Member I is composed of dolostones and conglomerates, while the overlying Member II is mainly composed of dolostones. Member III includes mudstones and siltstones, while Member IV consists of dolostones, cherty dolostones and minor limestones. The sedimentary facies is a mixed siliciclastic-carbonate platform and slope facies for the members I and III, and a carbonate platform margin and interior facies for members II and IV (Hu et al., 2021). The initial deposition of the studied formation is typified as a marine regression. Subsequently, a transgressive–regressive sequence occurred in members I and II. Member III is characterised by a marine transgression, and a subsequent regression occurred in Member IV (Ding et al., 2019).
Stratigraphy of the Gorstian and Ludfordian (upper Silurian) Hemse Group reefs on Gotland, Sweden
Published in GFF, 2021
Olof Taromi Sandström, Peter Dahlqvist, Mikael Erlström, Lena Persson, Steve Kershaw, Mikael Calner
New data from geophysical ATEM measurements, together with previously published and unpublished geophysical and field data reveal new insights to the Hemse Gp carbonate system. The lower Hemse Group (Ludlow, Silurian) on Gotland represents a transgressive systems tract, and thus the initiation of a carbonate platform cycle with deposition of marls and no or very limited reef growth. The end of the transgression, and thus maximum flooding of the basin within this sequence cycle, coincides with the Linde Primo-Secundo Event and marks the transition to a highstand systems tract with a strongly prograding barrier reef system.The Östergarn reef tract (sensu Flodén et al. 2001) shows a lateral transition from a typical barrier reef to the west and east of the Östergarn peninsula to a more rampiform setting at the actual Östergarn area (easternmost part of the Hemse Gp onshore Gotland).A facies association typical for the Kuppen-Snabben Unconformity Complex is recognised over a large area and contributes significantly to the interpretation that these erosive events influenced the inner, mid and outer ramp environments.The laterally extensive biostromal patch reefs system is significantly different from surrounding intra-reef areas and did probably form small islands during lowstand periods.
The Cambrian System in the Arrowie Basin, Flinders Ranges, South Australia
Published in Australian Journal of Earth Sciences, 2020
J. B. Jago, J. G. Gehling, M. J. Betts, G. A. Brock, C. R. Dalgarno, D. C. García-Bellido, P. G. Haslett, S. M. Jacquet, P. D. Kruse, N. R. Langsford, T. J. Mount, J. R. Paterson
The Wirrapowie Limestone of Haslett (1975) overlies the Woodendinna Dolomite to the north of the Wirrealpa Hinge Zone, where it intertongues with the Wilkawillina Limestone. The Wirrapowie Limestone comprises mainly dark grey laminated to well-bedded silty limestone and calcareous siltstone with minor interbeds of cross-bedded ooid limestone plus Renalcis-archaeocyath bioherms. In the type section in Wirrapowie Creek, the Wirrapowie Limestone is about 220 m thick (Haslett, 1975). At Warragee Bore in the central Flinders Ranges, Betts et al. (2016b) reported over 600 m of limestone that they assigned to the Wirrapowie Limestone. Here, the main lithologies are massive to laminated micritic limestones with common intraformational conglomerates. In the Bullock Head Gap area in the southwest of the Arrowie Syncline, Betts et al. (2017b, figure 7) reported about 160 m of shale within the Wirrapowie Limestone, which they assigned to the Midwerta Shale. Previous authors (Coats et al., 1973a, 1973b; Gravestock & Cowley, 1995; Zang et al.,2004) have regarded the Midwerta Shale as a lateral equivalent of the Mernmerna Formation. The Wirrapowie and Wilkawillina limestones represent restricted lagoonal and carbonate platform environments, respectively.