AN INTERESTING STYLE OF SAND-FILLED VEIN 



JOHN M. CLARKE 



The margins of Port Daniel bay in eastern Quebec are fringed 

 by vertical strata of Upper Siluric limestones rising in places to 

 bights of several hundred feet. Over the eroded edges of these 

 limestones are patchy deposits of the Bonaventure (Devono-Car- 

 bonic) sandstones and conglomerates, remnants of a sediment which 

 has extensively sheeted this region. 



At the east end of the bay, making the headland of Cap de 

 I'Enfer, the limestones are of red and yellowish hues and are fre- 

 quently seamed with vertical veins of inconsiderable size, these 

 being parallel to, not transecting the dip. Many of these veins 

 of quite irregular form resulting from an apparent deformation 

 by solution and shearing of the original crack, have been but 

 partially lined with deposition of calcite. The expanded portions 

 of the fissures may be left wide open and empty but more often 

 are filled by a regularly obliquely laminated deposit of dark red, 

 compacted and cemented sand. An excellent illustration of these 

 is shoAvn here, the vein occurring in a yellowish limestone, the top 

 being the eroded edge of the vertical stratum and the vein con- 

 tinuing down till it disappears in the water of the bay. The walls 

 of this fissure are coated with a thin deposit of calcite uniformly 

 laid on all surfaces, but nowhere meeting, while the cavities of the 

 expanded portions of the fissure are filled with layers of red sand 

 in curves concentric to the form which would result from depo- 

 sition by gravity. It is entirely evident that this deposit of sand 

 has infiltrated from the upper open mouth of the fissure, has sought 

 and filled the lowest cavities first and it will be noticed has also 

 filled the passage connecting the two lower cavities while the upper 

 cavity and the passage leading to it still remain open ready to 

 receive additional deposits. This red sand is very sharply lami- 

 nated and well compacted. Its color and composition leave little 

 doubt that it has been derived from the Bonaventure conglomerates 

 during the period of their erosion and that this erosion was ac- 

 complished before the fissure was wholly filled. There is no longer 



