Highlands. Both have different types of bedrock, impacting the nature of the stream and allowing for differences in aquifer development. The Mid-Hudson Valley region underlying most of Fishkill Creek consists of sedimentary rocks such as shales, sandstones, siltstones and dolomitic limestones that formed during the Cambrian and Ordovician periods of the Paleozoic Era, roughly 450–540 million years ago. These rocks become modified into metamorphic equivalents as a result of the formation of the Appalachian Mountains, which left large thrust faults in the area, the further east one gets from the Hudson. Shales become schists, limestones become marbles, and sandstone become quartzites in the eastern regions of Dutchess County. These rocks create better aquifers than their sedimentary counterparts. In the Hudson Highlands, the stream's bedrock is primarily metamorphic gneiss, with some granite and amphibolite. These are older rocks, formed in high temperatures and pressures more than a billion years ago in the Pre-Cambrian. These generally make poor aquifers, although individual houses can use one if they overlie a fault where groundwater collects. History The Iroquois tribes of the area called the stream Tioronda: "Little stream that flows into big water". Dutch settlers called it Vis Kill (Dutch for "fish creek") for the abundant fish in the stream. When control of the area passed to the English, it was Anglicized to Fishkill Creek (the addition of "Creek" creates a bilingual tautology, as kill is the Dutch word for creek, though this is not common knowledge to English speakers). In the late 17th century, two New York City merchants, Francis Rombout and Gulian Verplanck, bought , most of it in the creek's watershed, from the local Indians. Verplanck died before the transaction could be finished, and with his share divided among his heirs the land became known as the Rombout Patent. In 1709 his daughter Catheryna and her husband Roger Brett became the first European settlers in the Fishkill valley. She administered the subdivision and sale of the patent lands from her house, which still stands near downtown Beacon, the oldest continuously occupied house in Dutchess County. They also built the first mill on the creek in 1717. The upper Fishkill was settled around the same time. Henry Beekman, after boundary disputes with the Rombout patentees were resolved in their favor, obtained a crown grant of his own in 1703 for the lands now in the towns of Beekman and Union Vale. In