SHRIMP constraints on sediment provenance and transport history in the Mesozoic Statfjord Formation, North Sea

Abstract

Detrital zircons in sandstones of the Statfjord Formation (late Triassic-early Jurassic) in the northern North Sea have been dated with the sensitive high resolution ion microprobe (SHRIMP). These sandstones lack detailed biostratigraphic control, but display distinct variations in heavy mineral assemblages which facilitate a three-fold subdivision of the sequence. The lower and middle zones (heavy mineral Zones A and B) have similar characteristics, both displaying a marked upward decline in garnet abundance which has proved difficult to attribute unambiguously to change in either provenance or sedimentation history. The base of the highest zone (heavy mineral Zone C) is marked by changes in several heavy mineral indicators attributable to a shift in ultimate provenance compared with the underlying zones. The detrital zircon ages are a direct fingerprint of the sediment source terrains, and so resolve ambiguities in interpreting provenance from heavy mineral abundances alone. The age spectra indicate that both low-garnet and high-garnet parts of Zone A have the same ultimate provenance. This strongly suggests that garnet removal was not a function of changing provenance, but took place during the sedimentation process, probably by weathering during periods of prolonged alluvial storage. The source of Zone A is not represented in any presently exposed landmass: the required combination of Caledonian granitoids intruding or in immediate proximity to high-grade Archaean-sourced metasediments is likely to have been either to the west, in the northern part of the Shetland Platform, or to the north, in what is now the Norwegian Sea. Zircons in Zone C have a distinctly different age spectrum consistent with a source in the Western Gneiss Region of southern Scandinavia, where there is the required combination of Proterozoic protoliths and Caledonian reworking.

Heavy mineral as a tool to refine the stratigraphy of kaolin deposits in the Rio Capim Area, Northern Brazil

“…Analysis of dense minerals is widely used as a tool for stratigraphic correlation in sandstone dominated sequences lacking biostratigraphic control (Weissbrod and Nachmias 1986, Morton 1991, Morton and Hurst 1995, Mange-Rajetzky 1995, Smaler and Laird 1995, Morton et al 1996, Morton and Grant 1998, Hermann and Polozek 1999, Svendsen and Hartley 2002, Mange et al 2003. Other studies focusing sedimentary basins in northern and northeastern Brazil have shown that this type of approach using heavy minerals might be of a valuable tool for helping to establish the stratigraphic framework in areas where the sedimentary units display similar lithofaciological composition (Rossetti et al 1989, Sousa et al 2000, Nascimento and Góes 2005, Truckenbrodt et al 2005.…”

Provenance of deep-water reservoir sandstones from the Jubarte oil field, Campos Basin, Eastern Brazilian Margin

“…Results with more than 10% discordant were not considered in the probability plots. The number of analyzed grains is under the minimum recommended (Morton et al, 1996). Therefore, the interpretations were made under restrictions, since the data can be biased.…”

Tying catchment to basin in a giant sediment routing system: a source-to-sink study of the Neogene–Recent Amur River and its delta in the North Sakhalin Basin

“…12). The simultaneous changes in GZi and ATi values indicate that the packages of low GZi and ATi represent relatively intensively chemically weathered horizons, most likely prior to deposition (Morton & Berge 1995;Morton et al 1996). If the decrease in the GZi values was because of intrastratal dissolution of garnet during burial, then the ATi would remain unaffected, as apatite and tourmaline are both ultrastable during burial (Morton 1986;Morton & Hallsworth 2007).…”