normal tholeiitic basalt. The third hypothesis instead proposed at least three, but probably four separate pulses, with the olivine-rich magma being the final one. This was also conjectured through the use of whole-rock chemistry. Each of these theories supported the idea of crystal fractionation playing a significant, if not total, role in the differentiation of the sill. A single source for the magma was assumed. The latest conclusion reached for the origin of the intrusion was that the olivine in the olivine-rich zone could not have been in equilibrium with the rest of the body, indicating more than one source for the magma. This was determined through mass balance equations. It was also suggested that lateral flow within the still-liquid body played as important a role in differentiation as fractionation. Due to the interest in the subject, and a lack of a satisfactory conclusion, research on the Palisades Sill is currently ongoing. See also Diabase Igneous differentiation Sill (geology) Notes References Gorring, M. L., Naslund, H. R., 1995. Geochemical reversals within the lower 100 m of the Palisades sill, New Jersey. Contributions to Mineralogy and Petrology, v. 119, p. 263 – 276. Husch, J. M., 1990. Palisades sill: Origin of the olivine zone by separate magmatic injection rather than gravity settling. Geology, v. 18, p. 699 – 702. Lewis, J. V., 1907. The origin and relations of the Newark rocks. New Jersey Geological Survey Annual Report, 1906, p. 99 – 129. Lewis, J. V., 1908a. Petrography of the Newark Igneous Rocks. New Jersey Geological Survey Annual Report, 1907, p. 99 – 167. Lewis, J. V., 1908b. The Palisade diabase of New Jersey. American Journal of Science, 4th ser., v. 26, p. 155 – 162. Shirley, D. N., 1987. Differentiation and Compaction of the Palisades Sill, New Jersey. Journal of Petrology, v. 28, part 5, p. 835 – 865. Steiner, J. C., et al., 1992. A cumulus-transport-deposition model for the differentiation of the Palisades sill. "Geological Society of America Special Paper 268", p. 193-217. Walker, F., 1940. The differentiation of the Palisade diabase, New Jersey. Geological Society of American Bulletin, v. 51, p. 1059 – 1106. Walker, F., 1952. Late magmatic ores and the Palisade sheet. Economic Geology, V. 47, p. 349 – 351. Walker, F., 1956. The magmatic properties and differentiation of dolerite sills – A critical discussion. American Journal of Science, v. 254, p. 433 – 443. Walker, K.