Seashores, Soil Chemistry, and Hadrosaurs

Or how the need for a good soil conditioner lead to the discovery of New Jersey's state dinosaur.

Between 140 million and 70 million years ago, or during the Cretaceous and Tertiary periods, the action of the seas formed the coastal plain that today stretches from Newfoundland to the Yucatan. To the north and east of the Raritan River, subsequent glaciers would cover the original marine and coastal sediments. But in central New Jersey an exposed ridge formed from Cretaceous sediments gives us a glimpse into an ancient world.

During those 70 million years the sea levels repeatedly rose and fell many times. What is today northern New Jersey has still not been uplifted so that sometimes, the coastline was as far west as Scranton, Pennsylvania. At other times, the shoreline was found along a line running from New Brunswick to Trenton and thence down the west bank of the Delaware River as far as Willmington. And at other times, it ran along what we call today the continental shelf.

The earthÕs climate was warmer during the Cretaceous. Along the Jersey Shore, the ocean temperatures were mild year round and the coastline was lined with swamps and subtropical forests. At least 5 different species of dinosaurs inhabited this area along with marine reptiles, sharks, turtles, and thousands of invertebrate species. Two of the dinosaur species were Hadrosaurs, the Hadrosaurus foulkii and Hadrosaurus minor. They were tall, two-legged, duck-billed, herbivores. Because their bones are often found in marine sediments, paleontologists believe they adapted to life in coastal estuaries or along the banks of rivers. Skin imprints from Hadrosaur fossils in the western United States even show evidence of webbed feet. Some paleontologists believe that these animals lived in large herds, nesting in the uplands and periodically migrating to the shore. (New JerseyÕs first Shoebies?) Others believe that the animals lived there all year.

While the Hadrosaurs were grazing in the estuaries, coastal conditions were right for the formation of Glauconite (KMg(Fe,Al)(SiO3)6.3H2O). This is a greenish clay mineral in the mica family, which also contains Talc and Vermiculite. Formed under reducing conditions in marine environments, Glauconite consists of hydrated iron aluminum potassium silicates. It also contains trace amounts of phosphorous.

During a period of 140 million years, the seas would deposit some 12 to 24 (depending on which geologist is counting) distinct layers of clays, sand, gravels, and Glauconite-rich marls in what is today central New Jersey. (Marl is generic term for a mottled marine clay or shale. It often contains calcium in the form of fossil shells.) Some of the deposits are less than 20 feet thick, while the deepest extends 3,800 to 6,400 feet down to Precambrian rocks.

Except for some of the deeper formations, the Cretaceous and Tertiary sediments remained unconsolidated, that is, they never turned into rock. Subsequent soil formation and deposition left them largely uncovered or at least near the ground surface. By the time Europeans arrived this mineral wealth could be tapped with nothing more sophisticated that a shovel and a cart.

By the middle to late 1700Õs portions of New Jersey had already been farmed for more than a century and contrary to popular mythology, many colonial farmers were poor stewards of their soil. Visitors noted that some fields were so depleted that no crops would grow and they were reverting back to forest. For many the solution was to pack up and move west. Others used a crude form of crop rotation or used their depleted fields for grazing. In an era when all labor was done by muscle power and land was relatively cheap, it often made little sense to expend effort on the long-term care of the soil.

Not everyone shared this view. Both gentleman farmers and ordinary yeomen experimented with ways to restore soil fertility. Manuring and spreading lime were both well-known techniques. The use of wood ashes as soil conditioner was also coming into vogue. These were plentiful wherever land was being cleared. Other farmers tried plowing under rotting vegetable matter and even salt. Starting in the middle 1700s farmers began to try mudding (sic) their fields. Silt from streambeds, sand, and muck from swamps, were all mixed with soil. Some worked better than others and the mudd (sic) that worked best was the Glauconite-rich Greensand Marls of central New Jersey. This material was most commonly found in a belt some 6 to 13 miles wide and up to 30 feet deep stretching from the coastline south of Sandy Hook, through Freehold, Mullica Hill, Woodstown, and Salem. Substantial amounts were also found in Monmouth, Burlington, Gloucester, and Salem counties. The town of Marlboro in northwestern Monmouth County was named for the marls found there.

The idea of using Greensand Marls was slow to catch on. In 1815 several papers on the use of marl were presented at the Philadelphia Society for Promoting Agriculture. Marls had also been used in England as a soil conditioner since the 1600Õs. Sadly, the knowledge of its use did not cross the Atlantic with the first generations of English farmers. With steady persuasion however its use increased and by the time Henry Darwin Rogers was appointed State Geologist in 1835, some 80 farmers were mining and using the material.

As State Geologist, Henry Rogers gave the marl the name "Greensand" but was at a loss to explain its color. French marls were also green but those found in England could be gray, blue, yellow, or red. Rogers undertook the first systematic mapping of the beds. He also analyzed the material and determined that it consisted of silica, iron oxides, potash, lime, magnesia and water. This was very similar to results obtained by French chemists for the marls near Le Havre. English marls on the other hand, contained larger proportions of magnesia and only traces of potash.

Rogers published instructions so that farmers determine of their local marls contained enough Greensand for agricultural use. They should first make a rough estimate of the Greensand content using a magnifying glass. Then the marl should be washed to separate the clay from the Greensand. If accuracy was desired, the proportion of Greensand should be measured with an apothecary balance. Alternatively, the marl could be placed on a hot stove and the Greensand would turn red. Lastly the marl could be tasted. An inky taste indicated the presence of copperas (an iron sulphate) or aluminum sulphate. (Copperas was used at this time to make ink.) The presence of these materials would render the marl unsuited for agriculture.

By the middle 1800s mining marl had become a major industry. Cheap railroad transportation expanded the market for the material. In an era before commercial fertilizers were available, it must have seemed miraculous.

In the mid-1850s a professor of natural science and chemistry at Rutgers College named George H. Cook made another systematic study of the Cretaceous and Tertiary formations. He traveled extensively through the region carefully delineating, mapping and describing each one. But his greatest enthusiasm was for the Greensand Marls, which he promoted extensively among New Jerseys farmers. Appointed State Geologist after the Civil War, Cook used the 1868 Report of the State Geologist to advocate expanding the marl mining operations by consolidating smaller pits and even suggested that huge areas of central New Jersey be devoted to mining marls.

In 1858 William Parker Foulke, a member of the Academy of Natural Sciences, was on vacation in Haddonfield, New Jersey. Haddonfield was a sleepy, largely Quaker community whose main claim to fame was that it was the site of several Revolutionary War skirmishes. Foulke befriended a local landowner John Hopkins who showed the visiting scientist some enormous vertebrae that had been found in a marl pit some twenty years earlier. Foulke quickly obtained Hopkin's permission to dig in the abandoned pit. He hired some local marl diggers and after about ten feet of digging they found a layer of fossil seashells and large, heavy bones.

Foulke called in his fellow Academy member, Dr. Joseph Leidy, a professor at the University of Pennsylvania. Together they excavated what was then the most complete dinosaur skeleton yet discovered. Sadly, only a small portion of the lower jawbone was found and so the head of Hadrosaurus Foulke (literally Foulke's bulky lizard) remained conjectural. Hadrosaurus Foulke was the first mounted dinosaur skeleton to be displayed anywhere in the world as well as being the first dinosaur known to walk on two legs.

By the late 1800's marl had ceased to be an important fertilizer although it continued to be mined for use as a water conditioner. Today the Inversand Company in the Gloucester County town of Sewell runs the last-remaining Greensand mining operation in the United States. Most of the other the marl beds were largely forgotten except by paleontologists who to this day explore them for fossils. Leidy would go on to make many more important palentological discoveries both in New Jersey and throughout the United States. While George Cook was not primarily interested in fossils, he maintained his own contacts among the marl diggers and also accumulated a large number of specimens. Cook is best remembered today for his tireless efforts to bring the benefits of scientific agriculture to New Jersey's farmers. He was instrumental in having Rutgers designated New Jersey's Land Grant College in 1864. He also established the state's Agricultural Experiment Station in 1880. Cook College was named for him. Hadrosaurus Foulki was named the New Jersey State Dinosaur in 1991 after four years of lobbying by Joyce Berry and her fourth grade classes at Strawbridge Elementary School in Haddonfield.

Readers interested in learning more should consult, William Gallagher's When Dinosaurs Roamed New Jersey, Rutgers University Press, 1991; Jean Wilson Sidar's George Hammell Cook - a Life in Agriculture and Geology 1818-1889, Rutgers University Press, 1976; and Kemble Widmer's The Geology and Geology of New Jersey, D. Van Nostrand Company, 1964.