SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY. 1921. 



associations and generally in form and charac- 

 ter from the glauconite found at the strati- 

 graphic breaks. The latter is usually more 

 al)undant, is predommantly coarse (in grains 

 0.2 to 0.4 millimeter or more, rarely less than 

 0.1.5 millimeter in diameter), is less rounded and 

 less regular in shape, is at many stratigraphic 

 breaks fresher, is deeper in color, and is asso- 

 ciated with coarse quartz sand, generally some- 

 what finer than the glauconite, and with very 

 coarse fragments of fossils or with abundant 

 fossils. At some places it fills or penetrates 

 n-regularly the skeletons or hollows of the fossil 

 shells. It is commonly accompanied by very 

 abundant sulphide and in many occurrences by 

 fragments or nodides of brown, isotropic phos- 

 phate and by a peculiar opaque compact brown 

 substance, supposed to be some form of clay. 

 Tlie glauconite not associated with stratigraphic 

 breaks usually occurs in small, rounded grains, 

 which are scattered through less coarsely f ossil- 

 iferous limestone or shale and compared with 

 those found at the stratigraphic breaks look 

 as if they were transj^orted ami worn forms of 

 them.. 



The recognition of this association between 

 autochthonous glauconite and stratigi'aphic 

 breaks is essentially merely an extension and 

 application of the recognition by Cayeux * of 

 the connection between beds of phosphate and 

 movements of transgression and regression. 

 In fact, Cayeux begins his paper by calling 

 attention to the association of glauconite and 

 phosphate in the modern deposits of phosphate 

 by which he seeks to explain those of the geo- 

 logic past. 



With such thick beds of glauconite in mind 

 as those, for instance, of the Upper Cretaceous 

 of New Jersey it would appear unreasonable to 

 assert that glauconite occurs only in association 

 with stratigraphic breaks. Apparently the con- 

 ditions favorable to the formation of glauconite 

 ar<i characteristically associated with periods of 

 maximum emergence or, according to Barrell's 

 definition, with periods of maximum elevation 

 of base-level''' l)ut are not limited to this asso- 

 ciation. Cayeux formulates the law for the 

 Paris 15asin that "all the deposits [of phosphate 



* Cayeux, L., Gen&se ties giscmonts de pho-sphatcs do chaux s(.*di- 

 mentairt's: Soc. t^vnl. France Bull., 4th scr.. vol. .',. jip. 7.'>()~7o3, 1«)(),'>. 



^ Barrel], Joseph, Rhythms and the measurement of geologic time: 

 Gcol. ScH'. America Bull., vol. 2s, jip. 77s, 7s:i, i;tl7. 



of lime] of the Upper Cretaceous originated 

 during periods of great disturbances of the 

 equilibrium of the ocean." I would make the 

 corresponding generalization that in the sec- 

 tions I examined autochthonous glauconite 

 occurs in the "Bend series" only within a few 

 feet above stratigi-aphic breaks or, where there 

 is no break, only in direct association with max- 

 imum elevations of base-level. 



It must not be concluded that glauconite is 

 merely a shallow-water deposit coextensive 

 with coarse sand and other near-shore de- 

 posits. In the section from the Seaman well 

 I have recognized several stratigraphic breaks 

 that are marked merely by sand, without glau- 

 conite. Wliat assumptions may be made, 

 then, as to the special conditions favoring the 

 formation of glauconite? Cayeux, in the 

 paper cited, caDed attention to the fact that 

 modern accumulations of phosphate associated 

 with glauconite occur in areas of the ocean 

 where great destruction of life has been caused 

 by the meeting of a cold and a warm current. 

 But this is, as Cayeux recognized, too local a 

 phenomenon to account for widespread accu- 

 nmlations of dead organisms and is only one 

 of the disturbances of environment that might 

 result from a movement of base-level. Depth 

 of water and other elements of the environ- 

 ment woidd also change, and a change in any 

 of them might lead to the destruction of life 

 which would residt in the fonnation of phos- 

 phate deposits. But I do not think it should 

 be assumed that a change of environment over 

 a wide area, taking place suddenly, causes a 

 general destniction of life. The essential con- 

 dition seems to me to be that as a result of the 

 disturbances distinct marine envu'ouments 

 come into contact without any physical bar- 

 rier, and organisms passing from one to another 

 encounter imfavorable c'ontlitions and perish 

 in large num])ers and during a consideral)le 

 period of time. From this it can be deduced 

 that glauconite deposits associated with a move- 

 ment of base-level might not be ' everywhere 

 entirely contemporaneous, though from what 

 follows it will be evident that the time interval 

 between those formed in different parts of an 

 area as a residt of a given movement of base- 

 level is not great. 



The association of sulphide with sandy beds 

 in this section admits of two interpretations. 



