Examination of logs, core descriptions, stratigraphic cross sections, sand-isolith and structure maps, regional geology and paleogeography reveal the depositional environments of the Glauconite Sandstone in the Berrymore-Lobstick-Bigoray area to be distributary channels, delta platform, distributary mouth bars, and interdistributary bays.

Distributary channel-fill deposits are immature texturally and mineralogically. Their composition varies from submature feldspathic litharenites to immature (>10% clay) feldspathic litharenites. Siderite, ankerite and illite are early cements. Abundant ankerite and some pyrite are found associated with the erosional base of the distributary channels with abundant clay clasts. Zones of pore-filling hematite are present as intermediate to late stage cement. Pore-lining to pore-filling kaolinite, pore-bridging illite and coarse crystalline siderite are late-stage cements. Secondary porosity is formed from dissolution of feldspar and volcanic rock fragments.

Delta platform deposits are mature litharenites having secondary porosity due to dissolution of carbonate cements such as siderite and calcite.

Distributary mouth bar deposits are somewhat more mature texturally and mineralogically compared to channel deposits and can be classified as litharenites to quartz arenites. Secondary porosity is formed through dissolution of calcite cement.

Interdistributary bay deposits are composed of fine-grained sediments. Parallel laminae alternate with fine siltstone and silty claystone. X-ray mineralogy showed these samples to contain 7-13% kaolinite and 4-15% illite.

A simplified model for evolution of Glauconite Formation water compositions includes (1) original derivation in a deltaic setting giving composition of early pore waters as brackish to normal marine, (2) alteration due to inorganic and organic chemical diagenesis, and (3) dilution through time due to meteoric recharge. The formation waters now evolved have such a composition as to be (1) oversaturated with respect to hematite, kaolinite and illite (late-stage cements), (2) in near equilibrium to undersaturated with respect to quartz, calcite, siderite and dolomite.

The intermediate to late diagenetic cementation is a function of early diagenetic mineralogy. For example, hematite is formed by the oxidation of siderite due to meteoric water recharge. Oxidation of pyrite is quantitatively unimportant. Occurrence of late stage hematite is associated with structural highs which are most affected by meteoric water recharge.

The change in sand character, in terms of mineralogical and textural maturity, is found from delta plain deposits to delta front deposits present northeast of the paleohingeline which is parallel to paleoshoreline. Southwest of the paleohingeline the upper, delta plain (distributary channel) deposits are well isolated from the underlying, gas bearing delta platform deposits by abundant ankerite cement.