PALYNOSTRATIGRAPHY OF THE LATE CRETACEOUS MAGOTHY FORMATION OF DELAWARE AND MARYLAND

The Magothy Formation is a Cretaceous (Coniacian) formation consisting of interbedded sands, silts, and clays that is present in much of the coastal plain of Maryland, Delaware, and New Jersey. The sands are an important source of groundwater. The unit contains distinctive palynomorph assemblages composed primarily of angiosperm normapolles, tricolpate, and tricolporate types in addition to diverse trilete spores deposited in a deltaic to estuarine environment. These assemblages have been described in detail in previous works in New Jersey but only cursory attention has been paid to the palynology of this interval in Delaware. In this study, palynomorphs were examined in samples from a deep borehole (Je32-04) in central Delaware. Pollen from the lower part of the Magothy in Je32-04 resembled those found in the C. exigua- S. minor zone, whereas pollen from the upper part most closely resembled those from the P. cuneata- S. verrucosa zone. These findings suggest that these beds correlate with the South Amboy Fire Clay/Old Bridge Sand and Cliffwood/Morgan beds members of New Jersey respectively. Notable assemblage change across this interval includes a decrease in abundance of tricolpate types from the lower to the upper portion and a dramatic increase in the abundance of normapolles. These results will be integrated with work underway on other locations in Delaware and Maryland, including a recent (June 2021) corehole drilled in northern Delaware, a planned corehole in northeast Maryland, existing unworked core material from several sites in both states, and samples from several outcrops, including the area of the type section along the Magothy River and along the Chesapeake & Delaware Canal. Assemblages will be compared to those of the Magothy section of New Jersey, where the unit is much thicker and can be differentiated into distinct members, allowing regional correlation and assessment of lateral continuity of these members.