UNEARTHING NEW JERSEY NEW JERSEY GEOLOGICAL AND WATER SURVEY 2015 Department of Environmental Protection Vol. 11, No. 1 MESSAGE FROM THE STATE GEOLOGIST New Jersey has a natural treasure along her eastern border with the Atlantic Ocean in the form of nearly 130 miles of sun-soaked beaches where domestic and international tourists gravitate as the weather turns warmer. Over the years, we have featured several articles in Unearthing New Jersey about our long-running offshore sand resource exploration and beach nourishment program. That NJGWS program is critical to ensure our beautiful sand beaches, fanned by cooling fresh ocean breezes, will continue to be enjoyed by many for years to come. Among other topics covered in this edition, we dig below the sand at Sandy Hook, the northernmost point of the Jersey Shore, to investigate the sediments beneath. These sediments offer a unique record of sea-level rise and coastal View of Sandy Hook from Mount Mitchell Scenic Overlook, Atlantic High- environmental change since the last glaciation. The geologic lands Boro, Monmouth County. Bottom to top: Sandy Hook Bay, Sandy Hook, Raritan Bay, Brooklyn, (right), and Manhattan (left). On Sandy Hook, history of Sandy Hook is also detailed. center of photo, white building is Sandy Hook Lighthouse; on Manhattan, Our recent exploration of Sandy Hook is not the first time left of center, tallest building is One World Trade Center. Photo by Z. Allen- we have explored this peninsula. State Geologist George Lafayette H. Cook detailed, in his 1885 Annual Report, the outline of the “Hook” as it was that summer, drawn as curved contour COREHOLES REVEAL lines of equal elevation for every five feet above the mean GLACIAL AND POSTGLACIAL HISTORY tide. What is interesting to view is the Map of Sandy Hook (page 2), which shows the progressive changes in the shore AT SANDY HOOK line over 200 years of natural history. The map displays surveyed contour lines from 1885, 1853, 1844, 1836, 1732, By Scott Stanford, Ken Miller, and Jim Browning some time prior to 1764 and astonishingly from 1685, 330 years before to our recent glacial and postglacial study. Sandy Hook is a peninsula of beach sand that extends George Keith, Surveyor General of East Jersey (at that time, seven miles into Raritan Bay to form the northernmost point New Jersey was divided along its provincial line between of the New Jersey shore (fig. 1). The Hook rests on a thick East Jersey and West Jersey) surveyed the “Hook” in 1685 succession of estuarine and fluvial sediment deposited using hummocks as markers and plotted only a single within the past 25,000 years, as ice sheets in North America, line. However, the 1685 shore line on the 1885 map was Europe, Asia, and Antarctica melted and ocean levels rose. interpreted from the descriptions presented by George Keith This thick postglacial sediment was first recognized from on January 17, 1685. fossils found during the drilling of deep water wells for Fort Regardless of the accuracy of previous surveys, George Hancock, a former military base on the Hook, from the Cook stated in 1885 that, “it will be perceived that the Hook 1890s through the 1940s (Meredith E. Johnson, NJGWS has increased in length and in breadth so as to include more permanent notes). In the 1960s, James P. Minard of the than four times the area it covered in 1685 (compared to U.S. Geological Survey drilled auger borings along the Hook 1885)”, a process that continues today. that confirmed the presence of thick postglacial estuarine and beach sediments (Minard, 1969). Plant material in the Karl Muessig estuarine sediment at a depth of 85 to 92 feet in one of the New Jersey State Geologist auger holes was dated using radiocarbon to 11,300 years (11.3 ka) (9.8 ka in radiocarbon years), indicating that the sediments were postglacial. These studies suggested that postglacial sediments beneath the Hook are more than Ca5 [PO4]3 (F, Cl, OH) 250 feet thick, which would make them among the thickest postglacial sections accessible from land in the mid-Atlantic region. 1 Atlantic City, Cape May, Lewes, Delaware (across Delaware EXPLANATION Bay from Cape May), Reedy Point, Delaware (at the head of N SS Corehole Delaware Bay), and at Philadelphia. These gauges record th M1 sea level rising 3 to 4 mm/yr through the 20 century (Miller Well or boring and others, 2013). Sea level at earlier times is determined NMY M1 by coring and dating tidal-marsh deposits, which aggrade vertically as sea level rises. In the New Jersey area, these lighthouse Area of cores provide a record back to about 9 ka. The estuarine detail sediments beneath Sandy Hook could extend this record considerably, perhaps to before 14 ka. In addition to their record of sea level, the sediments may Monmouth FH M2 County also document hurricanes and other coastal storms. Large SS storms typically wash sand from barrier beaches into back bays and estuaries, leaving thin sand or gravel layers within muddy bay deposits. A geologic record of storms extending NEW JERSEY back thousands of years provides frequency and intensity M3 data that is not otherwise available. Such data is important Raritan Bay SMY when planning for rare events like Hurricane Sandy. Area of detail M4 To obtain sea-level and paleoenvironmental records, geologists at Rutgers University, in cooperation with the NJGWS, cored three test holes on Sandy Hook in May 2014. M5 The holes were drilled by the U. S. Geological Survey under contract to Rutgers, with funding from the NJDEP. The holes M6 were drilled to depths of 282 feet at the North Maintenance M7 Yard (NMY in fig. 1), 254 feet at the Salt Shed site (SS) and MONMOUTH COUNTY 172 feet at the South Maintenance Yard (SMY). The Salt Shed M8 and South Maintenance Yard holes penetrated Cretaceous Formations underlying the Quaternary section. The North 0 ½ 1 mi Maintenance Yard hole bottomed in Quaternary fluvial gravel M9 S beneath estuarine sediments. Coring recovers 2.5-inch- diameter samples in five- to ten-foot lengths. Sands can be Figure 1. Sandy Hook, with locations of coreholes and earlier wells and difficult to core as they have a tendency to flow out from, borings. Line of section in figure 2 shown in black. NMY=North Mainte- nance Yard corehole, SS=Salt Shed corehole, SMY=South Maintenance or jam inside, the core. For this reason, recovery was less Yard corehole, FH=Fort Hancock water well, M1-M9=auger borings from than 50 percent in the upper 50 to 70 feet of each corehole, Minard (1969). which is the depth of the beach and shoreface sand that makes up the Hook (Qbs in fig. 2). Silt, fine sand, and clay The sediments beneath Sandy Hook thus offer a unique in the underlying estuarine deposits are more cohesive than record of sea-level rise and coastal environmental change sand, and recovery of these sediments was nearly complete. since the last glaciation. The rise of sea level during the past The cores were described on site, and then brought to the century or so is recorded by tide gauges. In the New Jersey Rutgers core repository, where they are archived for future area, gauges with long records are situated at the Battery reference. Downhole gamma-ray geophysical logs of each in lower Manhattan, at the Coast Guard station at the north corehole were recorded by the NJGWS when drilling was end of Sandy Hook (just west of corehole NMY in fig. 1), in completed (red lines in fig. 2). Potassium and other elements in clay minerals produce more gamma radiation than sand- size minerals, which consist chiefly of quartz, so gamma NJGWS logs are a good indicator of clay content of the sediment. At 1835 the repository, the cores were described in detail by Rutgers and NJGWS geologists and organic material was sampled STATE OF NEW JERSEY for radiocarbon dating. Chris Christie, Governor Kim Guadagno, Lieutenant Governor GEOLOGIC HISTORY OF SANDY HOOK Department of Environmental Protection Bob Martin, Commissioner The great thickness of postglacial sediment beneath Sandy Hook is the result of the unusual glacial and postglacial Water Resources Management New Jersey Geological and Water Survey history of the Raritan and Hudson Rivers (fig. 3). Before the Karl Muessig, State Geologist last glaciation, the Hudson River flowed east of its current NJGWS Telephone: (609) 292-1185 location (fig. 3a). Based on the location and depth of former 29 Arctic Parkway FAX: (609) 633-1004 valleys now filled with glacial deposits, the Hudson flowed P.O. Box 420, 29-01 www.njgeology.org Trenton, NJ 08625-0420 down what is now the Harlem River, between Manhattan and the Bronx, and then southward across what is now Unearthing New Jersey 2 Vol. 11. No. 1 N NMY SS SMY S M1 FH M2 M3 M4 M5 M6 M7 M8 M9 0 Kns Qbs Qbs Kml 11.5 ka Kw Qms Qms -100 Kmt Qwf Qmm Ket elevation (feet) -200 glacial valley bottom Kwm Qst Kmg -300 EXPLANATION QUATERNARY CRETACEOUS SYMBOLS Beach and shoreface Navesink Woodbury and Dated organics Qbs sand Kns Formation Kwm Merchantville Formation Gamma-ray log- Estuarine sand and Magothy Formation intensity increases Qms Kml Mount Laurel Kmg to right mud Formation M1 Estuarine mud Wenonah Well or boring Qmm Kw Formation Postglacial fluvial Marshalltown Qst gravel Kmt Formation SS Corehole Glaciofluvial gravel Englishtown Qwf Ket Formation Figure 2. Cross section of Sandy Hook. Line of section shown on figure 1. Queens and Jamaica Bay (Buxton and Shernoff, 1999). southern edge of this outwash at the base of the Quaternary Geophysical surveys offshore between Long Island and New section, at a depth of 150 to 190 feet (Qwf in fig.