Geology of the Betterton Quadrangle, Kent County, Maryland, and a Di~Cussion of the Regional Stratigraphy
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Geology of the Betterton Quadrangle, Kent County, Maryland, and a Di~cussion of the Regional Stratigraphy GEOLOGICAL SURVEY PROFESSIONAL PAPER 816 Geology of the Betterton Quadrangle, Kent County, Maryland, and a Discussion of the Regional Stratigraphy By JAMES P. MINARD GEOLOGICAL SURVEY PROFESSIONAL PAPER 816 A description of Coastal Plain formations and a regional correlation with equivalent units to the northeast in Delaware and New Jersey UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1974 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 74-600006 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402- Price $1.20 (paper cover) Stock Number 2401-02558 CONTENTS Page Page Abstract 1 Stratigraphy of the Betterton quadrangle-Continued Quaternary deposits-Continued Introduction ------------------------------------ 1 Location and extent of area ------------------ 1 Holocene deposits ------------------------ 13 Purpose and history of investigation __________ _ 1 Bog -------------------------------- 13 13 Acknowledgxnents --------------------------- 4 Beach sand ------------------------ Previous investigations ----------------------- 4 Marsh deposits --------------------- 14 14 4 Alluvium --------------------------- Physiography ----------------------------------- Structure 14 Stratigraphy of the Betterton quadrangle -------- 5 Economic aspects ------------------------------- 14 Lower and Upper Cretaceous sediments ------ 5 Regional stratigraphy -------------------------- 15 Potomac Group -------------------------- 5 Lower and Upper Cretaceous sediments ------- 15 Upper Cretaceous sediments ----------------- 6 Potomac Group ------------------------- 15 Magothy Formation -------------------- 6 Upper Cretaceous sediments ----------------- 15 Merchantville Formation ---------------- 8 Magothy Formation --------------------- 15 Englishtown Formation ----------------- 8 Merchantville Formation ---------------- 19 Marshalltown Formation ---------------- 9 Englishtown Formation ----------------- 20 Mount Laurel Sand ---------------------- 9 Marshalltown Formation ---------------- 21 Tertiary sediments -------------------------- 11 Mount Laurel Sand ---------------------- 21 Hornerstown Sand _____________________ _ 11 Tertiary sediments -------------------------- 24 Vincentown Formation ------------------- 11 Hornerstown Sand ____________ ---------- 24 Quaternary deposits ________________________ _ 12 Vincentown Formation ------------------ 25 Pleistocene upland alluvium --------------- 12 References cited --------------------------------- 26 ILLUSTRATIO~TS Page PLATE 1. Geologic map and section of the Betterton quadrangle, Kent County, Maryland. _______________ In pocket FIGURE 1. Index map of the Coastal Plain from the Potomac River northeastward to Raritan Bay -------- 2 2-5. Photographs showing- 2. Cretaceous and Tertiary formations, Betterton quadrangle and nearby areas -------------- 7 3. Cross-stratified sand in the upland alluvium --------------------------------------------- 13 4. Heavy-mineral concentrations on the beach at Meeks Point ------------------------------ 14 5. Cretaceous and Tertiary formations in the northern Atlantic Coastal Plain ------------- 16 6. Generalized cross section of Cretaceous and Tertiary formations from the Betterton quadrangle to Raritan Bay ------------------------------------------------------------------------------ 18 TABLES Page TABLE 1. Modern correlations of Coastal Plain formations in Maryland, Delaware, and New Jersey ____ _ 3 2. Interpretation of stratigraphic section on the west side of Elk Neck ---------------------------- 19 3. Foraminifera from the coarse glauconitic bed near the stratigraphic middle of the Mount Laurel Sand, as mapped in the Betterton quadrangle----------------------------------------------- 22 4. Megafossils from the upper part of the Upper Cretaceous section along Lloyd Creek ------------- 23 11! GEOLOGY OF THE BETTERTON QUADRANGLE, KENT COUNTY, MARYLAND, AND A DISCUSSION OF THE REGIONAL STRATIGRAPHY By jAMES P. MINARD ABSTRACT Bay, at the confluence of the Sassafras River with Eight Coastal Plain formations crop out in the Betterton the bay, due east of Baltimore (fig. 1). About 4-5 quadrangle near the inner edge of the Atlantic Coastal Plain square miles of the area of the quadrangle is water, physiographic province. The quadrangle is in Kent County on the Eastern Shore of Chesapeake Bay, east of Baltimore, mostly across the northern part. The quadrangle is Md. The eight stratigraphic units constitute a total sec entirely within Kent County, Md. tion of about 300 feet. In ascending order, the units are: The upper part of the Potomac Group, the Magothy, Mer PURPOSE AND HISTORY OF INVESTIGATION chantville, Englishtown, and Marshalltown Formations, and the Mount Laurel Sand, all of Cretaceous age; and the Geologic study of the Betterton quadrangle was Hornerstown Sand and Vincentown Formation of Early undertaken as a projection of detailed quadrangle Tertiary (Paleocene) age. Quaternary deposits are Eeparated into five map units. mapping by the author and J. P. Owens along the The most extensive and thickest (as much as 145 ft) is ths inner edge of the Coastal Plain in New Jersey. The upland alluvium which blankets nearly all the surface area Betterton quadrangle is on a southwest extension of of the quadrangle exeept where incised by stream valleys. a straight line through four of these quadrangles The other Quaternary units are small in areal extent and (fig. 1). The mapping in New Jersey was the first reach a maximum thickness of possibly 30 feet. They are mapped as bog, beach sand, marsh deposits, and Holocene modern detailed mapping of a large area at a large alluvium. scale in that State. Geologic mapping has been com The generally unconsolidated Cretaceous and lower Ter pleted in twelve 1112-minute quadrangles (1 :24,000 tiary formations consist chiefly of quartz, clays, muscovite, scale) ; maps or reports on 11 of these quadrangles chlorite, lignite, feldspar, and pyrite. Quaternary sediments are largely sand and gravel with lesser amounts of silt, clay, have been published (Minard, 1969, fig. 2). This muck, and peat. mapping allowed for accurate correlation along the The Cretaceous and Tertiary units strike generally north entire 100-mile strike of the Coastal Plain forma east in the region, but trends in the quadrangle range from tions in New Je~sey. nearly east-west to north-south. The units appear to be gently warped. Concurrent reconnaissance mapping and investiga Resources include ground water, peat, and vast quan tions were conducted in Delaware in an attempt to tities of sand and gravel. Appreciable concentrations of correlate the Coastal Plain section of that State ilmenite are locally present, but no ore bodies ar·e known. (made prior to 1969) with the section in New Jersey. The Betterton and adjoining quadrangles contain out As can be seen on table 1, the Coastal Plain stra crops of most of the Cretaceous and Tertiary formations of the Coastal Plain. It is the farthest southwest, on the East tigraphy recognized by the Delaware Geological Sur ern Shore of Chesapeake Bay, that so many formations are vey (prior to 1969) could be only partly correlated exposed. Some units have been eroded, overlapped, or un with the Coastal Plain stratigraphy in New Jersey. dergone facies changes along the strike from northeast to In 1967, the section as mapped in the Woodstown southwest, but the remaining units can be traced to or quadrangle, New Jersey (Minard, 1965), was tenta correlated with sections in Delaware, and throughout New Jersey. tively established for Delaware by publication of a special map by the U.S. Geological Survey (1967) INTRODUCTION (actually nearly the same section Carter attempted to establish in 1937). This was followed 2 and 3 years LOCATION AND EXTENT OF AREA later by acceptance of the U.S. Geological Survey The Betterton quadrangle encompasses nearly 58 section by the Delaware Geological Survey (Pickett, square miles on the Eastern Shore of Chesapeake 1969, 1970a). 1 2 GEOLOGY OF THE BETTERTON QUADRANGLE, KENT COUNTY, MD., AND REGIONAL STRATIGRAPHY In 1970, Owens and others (1970) correlated the naissance field geology in Delaware (particularly in post-Magothy formations of New Jersey, Delaware, 1963) and in eastern Maryland during this same and eastern Maryland. The report was based on the period. New Jersey work from 1957 to 1965, and on recon- In 1965, a mapping program, the Upper Chesa- n· 76" 75" 74" T T T T ~ ~~I PENNSYLVANIA ~/ ~~q.~,."" ,~"!:""'"" Roosevelt quadrangle renton/ D (Minard, 1964) 40" + NEW JERSEY Mount Holly quadrangle (Minard and others. 1964) sw D ----- MARYLAND /JELA WARE HA r DELAWARE VIRGINIA 20 40 MILES FIGURE 1.-Index map of the Coastal Plain from the Potomac River northeastward to Raritan Bay. INTRODUCTION 3 TABLE 1.-Modern correlations of Coastal Plwin formations in Maryland, Delaware, and New Jersey Maryland Delaware New Jersey Betterton quadrangle U.S. Geol. Owens and Minard, Cleaves and others, Jordan, Survey, Pickett, 1960, and Minard, This report 1968 1962 1967 1970b 1964, 1969 Cohansey Sand Chesapeake Chesapeake Chesapeake Group Group Group Kirkwood Formation Piney Point Piney Point Formation Formation Nanjemoy Manasquan Formation Formation - Rancocas A quia Vincentown Vincentown Vincentown Formation Formation