Bees Sandstone Research Articles

Authigenic iron and titanium oxides in triassic red beds: (St. Bees Sandstone), Cumbria, Northern England

AbstractAuthigenic iron and titanium oxides occur in three main textural varieties in the St. Bees Sandstone, a Triassic red bed succession in Cumbria. These are: (a) overgrowths of haematite, titaniferous haematite, anatase, and rutile which generally occur on detrital host grains of similar compositions. The overgrowths may occur as syntaxial rim cements or rhombohedral and prismatic projections and are always in optical continuity, (b) discrete crystals of anatase (including octahedrite) and haematite 10‐40 μm in size occur in pore spaces, and (c) fine grained ( < 1 μm) pigmentary haematite occurs as grain coatings around detrital grains and in the interstitial matrix.The euhedral nature and pore‐filling habit clearly indicate the authigenic origin of these iron‐ and titanium oxides. All three textural varieties are believed to have been precipitated from ground waters containing dissolved ferrous and titanium ions. These ions were derived from the intrastratal solution of detrital iron and titanium bearing grains including ferromagnesian silicates and iron‐titanium oxides. The precipitation of iron oxides from migrating ground waters in the manner described here goes some way to explaining how thick, uniformly red successions can be formed.

Authigenic iron and titanium oxides in Triassic red beds: (St. Bees Sandstone), Cumbria, Northern England

AbstractAuthigenic iron and titanium oxides occur in three main textural varieties in the St. Bees Sandstone, a Triassic red bed succession in Cumbria. These are: (a) overgrowths of haematite, titaniferous haematite, anatase, and rutile which generally occur on detrital host grains of similar compositions. The overgrowths may occur as syntaxial rim cements or rhombohedral and prismatic projections and are always in optical continuity, (b) discrete crystals of anatase (including octahedrite) and haematite 10‐40 μm in size occur in pore spaces, and (c) fine grained ( < 1 μm) pigmentary haematite occurs as grain coatings around detrital grains and in the interstitial matrix.The euhedral nature and pore‐filling habit clearly indicate the authigenic origin of these iron‐ and titanium oxides. All three textural varieties are believed to have been precipitated from ground waters containing dissolved ferrous and titanium ions. These ions were derived from the intrastratal solution of detrital iron and titanium bearing grains including ferromagnesian silicates and iron‐titanium oxides. The precipitation of iron oxides from migrating ground waters in the manner described here goes some way to explaining how thick, uniformly red successions can be formed.

Diagenetic development of unstable and stable magnetization in the St. Bees Sandstone (Triassic) of northern England

Thermal demagnetization of red and drab sandstones from the St. Bees Sandstone shows a wide range of directional stability. After the removal of a metastable secondary magnetization at temperatures up to 300°C red sandstones may show stable or unstable magnetization. Experiments indicate that both the stable and unstable magnetization is carried by coarse haematite particles (specularite). Drab sandstones, which have been subject to reduction and dissolution of haematite are generally unstable but specimens with a stable NRM occur and this must be carried by specularite because the pigment has been removed from these specimens. The stable magnetization is believed to have developed during deposition and early diagenesis by the oxidation of detrital iron oxides. Pole positions correspond to known Triassic poles and there are abundant normal and reversed zones typical of the Lower Triassic. The unstable magnetization of the red sandstones is apparently due to the development of authigenic overgrowths of haematite on the detrital specularites. This phase of authigenesis may have taken place over a long time, and after significant changes in the ambient geomagnetic field resulting in complex magnetizations in individual grains and hence whole rocks.

The Petrography of the Triassic Sandstone of North-East Ireland

Between the years 1869–83 the Triassic sandstone of North-East Ireland was examined and mapped by the Geological Survey under the direction of Hull. The rocks were correlated with those of similar age in Lancashire and Cheshire, the lithological characters described and the exposures noted. Later the Belfast district was resurveyed under the direction of Lamplugh, who suggested, in the Memoir published in 1904, that the Triassic sandstone should be correlated with the St. Bees sandstone rather than with that of Lancashire and Cheshire. Attention was also drawn to the probable incorrect mapping of the Trias near Belfast.

XXII. The Annan Red Sandstone Series of Dumfriesshire

The post-Carboniferous red sandstones of the south-west of Scotland are found in a series of isolated areas which cover about fifty-four square miles. They include two sets of rocks——(1) a succession of strongly false-bedded sub-aerial sandstones, which may be termed the Dumfries Series, and (2) an area of interbedded red sandstones and shales which may be conveniently grouped as the Annan Series. Of the false-bedded Dumfries Sandstones the chief outcrops are around Dumfries, as at Locharbriggs, Lochmaben, Corncockle, Lockerbie, Closeburn, and Moffat. They are also exposed at Loch Ryan, Mauchline in north Ayrshire, and Arran. The interbedded red sandstones and shales extend, north of the Solway, from the neighbourhood of Annan eastward to the English Border. The differences between these two groups of deposits are so well marked that they have generally been referred to two distinct horizons. The false-bedded sandstones closely resemble the Penrith Sandstones (Lower Permian), and the sandstones east of Annan are equally similar to the St. Bees Sandstone (Bunter), with which direct stratigraphical continuity has been proved around the eastern end of the Solway. The false-bedded Dumfries Sandstones have therefore been generally accepted as Lower Permian and the Annan Sandstones as Triassic. This view was expressed by Harkness in 1850 (p. 397); he concluded from the lithological and palaeontological evidence that the sandstones east of the river Annan are superior in position to those of the neighbourhood of Dumfries. He repeated this view in 1856 (p. 267), when he remarked that in south-western Scotland most of This 250-word extract was created in the absence of an abstract

V.—A Chemical Examination of the St. Bees Sandstone of West Cumberland

The following analyses were made to ascertain the magnitude of local variations in the St. Bees Sandstone of West Cumberland. It will be convenient for this purpose to consider the district as follows:—The area south of St. Bees, as far as Calder Bridge.The area north of Maryport, as far as Wigton.

V.—On the Evidence as to the Geological Structure of Cumberland bordering the Solway

While no doubts have existed among geologists that the rocks of this district are of Permo-Triassic age, that they are surrounded by older formations of the Carboniferous Series, and capped by a small Lias outlier, unanimity as to the relations of the local Perrao-Triassic rocks to each other has never yet prevailed. Hence when the Geological Survey Memoir, by the present writer, on this district was published in 1899, Sir Archibald Geikie stated in the preface tliatthe delay in its appearance was due to the hope that additional deep borings might have settled certain questions as to the relations to each other of the rocks above the St. Bees Sandstone, etc. On this account, my own views (as those of the worker on the Geological Survey in this district) were allowed to be given by me in a paper read at the Geological Society in 1881, on “The Permian, Triassic, and Liassic Rocks of the Carlisle Basin” (Q.J.G.S., vol. xxxvii, May, 1881).

The St. Bees Sandstone

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