Green Clay Minerals

Unconformity generation and the shift from storm‐dominated to tide‐dominated processes in a Jurassic retroarc foreland basin: Insights from ichnology

“…Glauconite formation typically occurs in open marine environments with limited terrigenous input and low rates of sediment accumulation (Hesse & Schacht, 2011; Velde, 2014). Optimal conditions appear to exist on the outer shelf/upper slope, although occurrences down to 2,000 m water depth have been reported (Odin & Stephan, 1981).…”

“…Apertures are preserved in some specimens in FA 3 at Glendo Reservoir; they are characterised by a broadening of the tunnel diameter with a radial pattern of scratch marks fanning outward, and their apex at the aperture. Examples of this architecture are abundant in very fine‐grained, sand‐prone storm beds (FA3) of the Redwater Shale at Seminoe Reservoir, their occurrence in association with the abundant glauconite, are considered proxies for relatively low rates of sediment accumulation (Hesse & Schacht, 2011; Velde, 2014) and compaction‐induced dewatering (Figure 11K).…”

Chlorite coating patterns and reservoir quality in deep marine depositional systems – Example from the Cretaceous Agat Formation, Northern North Sea, Norway

“…This interpretation is based on observed features like the presence of clay at grain contacts, the tendency of thicker coating in grain indentations and the lack of clay bridging between detrital grains (Figures 7, 8 and 10) (Wilson, 1992). Furthermore, the mineralogical data show that the sandstones of the Agat Formation comprises abundant green marine clay pellets in certain intervals (Table 2 and Figure 7c), some of which show a glauconitic composition (Figure 7a,b,g), which can be associated with a shallow marine origin (Velde, 2003). The phosphatic clasts are also likely to represent shelfal material and could indicate that they originated from an environment near a site of ocean upwelling (Velde, 2003).…”

“…Furthermore, the mineralogical data show that the sandstones of the Agat Formation comprises abundant green marine clay pellets in certain intervals (Table 2 and Figure 7c), some of which show a glauconitic composition (Figure 7a,b,g), which can be associated with a shallow marine origin (Velde, 2003). The phosphatic clasts are also likely to represent shelfal material and could indicate that they originated from an environment near a site of ocean upwelling (Velde, 2003). The depositional environment of the Agat Formation have been debated in the literature, for example from slumps and debris flow‐dominated (Shanmugam et al., 1994; Skibeli et al., 1995) to turbidity current‐dominated environments (Nystuen, 1999) but with a general agreement that the Agat sands were deposited in a slope setting.…”

Life in the woods: Taphonomic evolution of a diverse saproxylic community within fossil woods from Upper Cretaceous submarine mass flow deposits (Mzamba Formation, southeast Africa)

“…Glauconite is generally considered to precipitate via partial reduction of iron in faecal or other sedimentary pellets that accumulate on the sea floor (Thompson and Hower, 1975). Glauconitization occurs mostly in semi-restricted marine microenvironments, in potassium-rich, porous sediments with a pH around 8 (although pH conditions can be quite variable) and a temperature below 15 °C, at times with little or no detrital deposition (i.e., intervals of starved sedimentation), although iron-rich fluvial input can enhance glauconite formation (Odin, 1988;Velde, 2014). In modern marine environments it typically accumulates in sediments at around 200 m water depth (Porrenga, 1976), consistent with our interpretation of a shelf setting below storm wave base, although it can also form at shallower depths given appropriate physico-chemical conditions.…”