UPPER CRETACEOUS. 659 



glauconitic in places throughout the formation, and toward the top occur rather massive inter- 

 bedded layers of glauconitic sand some of which bear marine invertebrates. The clays carry 

 fossil leaves in various stages of preservation. The sands and clays are believed to be in part 

 of estuarine and in part of marine origin. An Upper Cretaceous terrane which has not been 

 differentiated in North Carolina but which is developed in South Carolina from Chesterfield 

 County southwestward consists mainly of light-colored clays and coarse arkosic sands. These 

 beds, designated the Middendorf beds by Sloan,^*^'' although hthologically different from the 

 Black Creek, and evidently of shallower-water origin, are regarded by E. W. Berry, on the evi- 

 dence of fossil plants, as contemporaneous with the lower portion of the Black Creek formation, 

 and they are treated as a member of the Black Creek under the name Middendorf arkose member. 



The Black Creek formation rests unconf ormably upon the Lower Cretaceous deposits of the 

 region and is overlain by the Peedee sand. The typical beds of the Black Creek formation occur 

 in the valley of Peedee River and its tributaries in parts of Marion, Florence, Marlboro, and 

 Darlington counties, and the Middendorf arkose member appears in a relatively narrow area 

 from Chesterfield County southwestward to Aiken County. The failure of the upper part, of 

 the Black Creek formation to appear at the surface to the south and the narrowing down of the 

 Middendorf member in that direction are due to an overlap of Eocene beds from the southeast. 

 Over much of the area of its occurrence the formation is concealed at the immediate surface by 

 thin surficial deposits of late Tertiary or Pleistocene age. 



The Peedee sand received its name from Peedee River, South Carolina."^^ It was later desig- 

 nated by Sloan '*''^"'' the "Burches Ferry marl." The formation consists of 800 feet or more of 

 marine sands and clays, more or less calcareous and glauconitic, carrying marine invertebrates. 

 It appears at the surface in bluffs of Peedee River and its tributaries in Florence, Williamsburg, 

 Georgetown, Marion, and Horry counties and is present in considerable areas in these counties 

 beneath thin patches of Tertiary deposits and beneath a thin but almost continuous covering of 

 Pleistocene and Recent deposits. Southward from this area the formation is overlapped and 

 completely buried by Eocene strata. 



As previously stated, the Upper Cretaceous formations of this State constitute the south- 

 ward continuation of deposits which have their most extensive areal distribution in North 

 Carolina. More complete collections of fossil leaves and invertebrates have been made in that 

 State than in South CaroUna, and it is largely on the results of paleontologic investigation 

 carried on in North Carolina that the following attempt at correlation with Cretaceous deposits 

 ia outside regions is based. The plants have been studied by E. W. Berry and the invertebrates 

 by the writer. 



The invertebrates present in the upper part of the Black Creek formation indicate a pre- 

 Peedee, or, in terms of the Maryland-New Jersey section, a pre-Monmouth age of the beds con- 

 taining them. Tliis part of the formation would appear, therefore, on this evidence to be 

 synchronous with a part of the Matawan formation. The plants which occur throughout the 

 vertical extent of the formation, being interbedded with the invertebrates in the upper part of 

 the terrane, constitute a flora, according to Berry, analogous with that contained in the Magothy 

 formation of Maryland and New Jersey, the Matawan formation in these States not having 

 jrielded any considerable flora. The Black Creek beds below the invertebrate-bearing beds of 

 the formation are doubtless referable, therefore, in part or in whole to the Magothy formation, 

 but the presence of the flora in supposed Matawan equivalents in the Carolinas would seem to 

 indicate its persistence here to a later time than the record preserved in the New Jersey-Maryland 

 deposits would indicate. 



Referred to the Upper Cretaceous deposits of the Chattahoochee region (Georgia-Alabama) 

 the invertebrates in the upper beds of the Black Creek indicate close synchroneity with the 

 beds exposed along Chattahoochee River from Roods Bend, in Stewart County, northward to 

 the vicinity of Florence, in the same county, or to that part of the Ripley formation below the 

 beds characterized by the presence of Exogyra costata Say. Fossil plants referable to the Black 

 Creek flora have been found at several horizons from beds at the extreme base of the Upper 

 Cretaceous deposits (Eutaw formation) of the region up almost to the base of the beds carrying 



