Angiosperm pollen zonation of the continental cretaceous of the Atlantic coastal plain and its application to deep wells in the Salisbury embayment

Abstract

Abstract This paper presents and illustrates an informal palynological zonation of the pre‐Magothy continental Cretaceous sediments of the Atlantic Coastal Plain (Potomac Group, Raritan Formation), based primarily on new and previously published studies of angiosperm pollen from two wells near Delaware City, Delaware, and from outcrop samples from Virginia through New Jersey, following lines established by Brenner (1963). Monosulcate angiosperm pollen (with columellar exine structure) is present from the base of Brenner's Zone I (Patuxent Formation and Arundel Clay equivalents, Barremian‐lower Albian?). Reticulate tricolpates enter in upper Zone I and diversify in Brenner's Subzones II‐A and II‐B (Patapsco Formation equivalents, middle‐upper Albian?); tricolporoidates appear in Subzone II‐B. Very small, psilate tricolporoidates and Rugubivesiculites rugosus enter in our Subzone II‐C (uppermost Albian?), larger triangular tricolporates and new tricolpates in Zone III (lower Cenomanian?); these two units are represented in “Maryland Raritan”; or Elk Neck beds. The first triporate Normapolles (Complexiopollis, Atlantopollis) appear in Zone IV (lower part of the true Raritan Formation of New Jersey, middle Cenomanian‐lower Turonian?), additional Normapolles in Sirkin's Zone V (upper part of the Raritan, middle Turonian‐lower Santonian?). Application of this zonation shows that all but the top of the very thick continental‐nearshore marine section in three deep wells in the Salisbury Embayment (Hammond, Bethards, Taylor) is of Early Cretaceous age (though in part older than the outcrop Potomac Group), including “red beds”; previously considered Triassic or Jurassic. Maximum marine incursions occurred in the late Albian and early Cenomanian. Equivalents of the Raritan Formation of New Jersey (Zone IV), lacking at the Maryland‐Delaware outcrop, are identified for the first time in the Taylor and Bethards wells. Potomac and lower Raritan equivalents are separated from overlying Magothy Formation equivalents (upper Santonian‐Campanian?) by a regional unconformity.