Geology

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Arkose

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A sedimentary rock made from sand and gravel, containing a mixture of minerals such as quartz and feldspar grains, along with mud or clay. The reddish-brown iron minerals that cement arkose rock in Connecticut have led to its commercial name of "brownstone."

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Atreipus

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Abundant footprint species, with 3-toed hind feet and smaller 4-toed forefeet, made by a 4-footed ornithischian dinosaur about 6 feet long.

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Basalt

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The most abundant volcanic rock, typically occurring as dark-gray lava (surface) flows and as dolerite in (sub-surface) dikes and sills. The fine-grained texture and hard brittle nature make basalt valuable for construction fill, and it is widely quarried in Connecticut under its commercial name of "traprock."

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Basin

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A large valley or low region developed by subsidence, where sediments have collected.
Bronson Hills A terrane extending north-south along the eastern side of the Connecticut Valley, thought to be formed by the collision of an ocean volcanic arc sometime in the early Paleozoic

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CAMP

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Acronym of the Central Atlantic magmatic province, a great region of basaltic volcanism that occurred about 200 million years ago along a zone where central Pangaea would rift to form the new ocean.

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Cenozoic

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The Era between 65 million years ago and today, named from the Greek words for "Recent Life." Especially distinguished by mammals.

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Coelophysis

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A small bipedal carnivorous dinosaur from the Late Triassic of North America, which may be responsible for some of the tracks called Grallator. Bones of Coelophysis are rare in Connecticut but locally abundant in the western USA.

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Conglomerate

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A sedimentary rock made from large and small rounded stones, mixed together in all sizes. Often characteristic of high-energy water bodies such as mountain streams, riverbeds, and shorelines.

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Cretaceous

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The Period between 145 and 65 million years ago, named for the Latin word for chalk, of the cliffs on the English Channel. Cretaceous rocks are no longer present in Connecticut, but they exist in Long Island Sound as well as farther south and east

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Dike

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A cross-cutting Earth fracture intruded by magma (often basalt), which has cooled in place. Dikes are usually a few feet to tens of feet thick, and examples in Connecticut include the Bridgeport Dike, Buttress dike, Fairhaven dike, and Higganum dike, from west to east. Large dikes such as these examples probably fed fissure volcanoes with massive lava flows.

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Dilophosaurus

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An Early Jurassic theropod dinosaur that stood about 8 to 10 feet high and had two distinctive crests on its head. This animal might have made Eubrontes footprints.

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Dolerite

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A dark gray, fine to medium grained igneous rock that cooled within the Earth in dikes and sills (intrusive). Dolerite closely resembles basalt, which is essentially the same magma that passes upward through dike and sill fractures before cooling in volcanic (extrusive) lavas

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Eubrontes

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Common large "footprint species" made by a 3-toed bipedal theropod up to 18 feet long, similar to (possibly the same as) the famous head-crested Dilophosaurus. This track is the Connecticut state fossil.

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Fissure eruption

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A type of volcano in which the lava pours from a long (some a hundred miles or more) Earth fracture rather than from eruption single place or mountain. A lava curtain at the fissure may shoot several hundred feet into the air, as seen in smaller fissure eruptions in modern Iceland or Hawaii.

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Fossil

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The physical evidence for ancient (prehistoric) life, which may be actual remains such as bones, or forms preserved by minerals and sediments, such as footprints or worm borrows.

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Grallator

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Footprint species made by a small bipedal theropod in Early Jurassic time, which was a nimble hunting dinosaur about 4 to 5 feet long. Possibly they are tracks of Coelophysis, but several species could fit.

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Hornito

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A structure in lava where gases from below a lava flow have broken upward to the surface, often causing a mound of new material on the surface and a zone of broken rock and new minerals along the fracture pathways.

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Ichthyosaurs

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Large marine reptiles that looked much like modern dolphins.

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Jurassic

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The Period between 201 and 146 million years ago, named for the Jura Mountains in Europe. The Early Jurassic is represented in Connecticut by rocks and fossils.

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Lava

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The rock that as a liquid magma was emitted onto the surface by a volcano, and which may flow for long distances if hot and fluid enough. After cooling and solidifying, thick strata of lava may be preserved if covered by later materials; otherwise if exposed at higher surface elevations, lava generally is quickly eroded in humid climates. Most lava in Connecticut is basalt (also see traprock).

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Mesozoic

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The geological Era between 250 and 65 million years ago, named with the Greek words for "Middle Life." Especially distinguished as the Age of Dinosaurs. Connecticut has rocks and fossils from the middle part of the Mesozoic Era, or roughly between 230 to 180 million years ago.

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Ornithischia

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"Bird hip" suborder of the Dinosaurs, which in mid-Triassic time formed along with the Saurischia suborder. Later developments of Ornithischia include the Ornithopods,
Ceratopsids, Stegosaur, and Anklyosaur families. All were herbivores. Despite the name, birds are not descended from ornithischians.

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Paleozoic

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The Era between 545 and 250 million years ago, named from the Greek words for "Early Life." Paleozoic fossils are dominated by marine invertebrates. Pangaea was assembled during the Paleozoic Era.

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Pangaea

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The super-continent (from the Greek for "all one Earth") that existed during the early part of the Mesozoic Era. The region that became Connecticut was in the central part of Pangaea, at a tropical latitude. Also spelled Pangea.

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Phytosaurs

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A common group of four-footed Triassic aquatic reptiles, including the ancestors of crocodiles. All except the crocodiles died out in the end-Triassic extinction.

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Plesiosaurs Large

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long-necked, four-finned marine reptiles, similar to depictions of the mythical Loch Ness Monster.

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Pterosaurs

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A group of flying reptiles that were contemporaries of dinosaurs, ranging in size from modern birds to soaring animals with 40-foot wingspans. The big-headed pterosaur depicted at Dinosaur State Park is called Dimorphodon

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Radiometric

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Measurement system using radioactive isotopes, important for age determinations of rocks and fossils.

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Saurischia

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"Lizard-hip" suborder of dinosaurs, which divided into theropods and sauropods in the Late Triassic and became much more important during the Jurassic Period.

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Sauropods

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Large long-necked four-legged plant eaters, including the largest of all land animals, with examples that were best developed (and more famous) from Late Jurassic time

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Sill

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Sub-surface igneous intrusion of a conformable, usually near-horizontal or low-angle Earth fracture that has been filled by magma (often basalt). Sills may be hundreds of feet thick, and in Connecticut they include Sleeping Giant, West Rock, and East Rock.

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Squamates

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The group name of lizards and snakes, which had its earliest members in Late Triassic time.

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Strata

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Layers within the upper section of the Earth, usually made from sediments, and where present, lava flows and ashes. Stratigraphic names may be assigned to major continuous layers, and the subject in general is called stratigraphy.

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Subduction

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The plate tectonic process in which sections of the Earth’s ocean crust are pushed downward into the mantle, which occurs along zones of plate collisions or convergence.

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Tethys Ocean

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A section of the ancient ocean or sea along the eastern side of Pangaea, about where the Mediterranean Sea and Indian Ocean are today.

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Thecodonts

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A group of primitive reptiles, which were Triassic precursors to dinosaurs

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Theropoda Saurischian

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dinosaurs that were bipedal, agile, and carnivorous, including Dilophosaurus and later animals such as Allosaurus. Members of this group are believed to be the ancestors of birds, which had appeared by the Late Jurassic.

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Terrane

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A section of the Earth’s crust with a geologic history distinct from neighboring terranes. Continents are assembled from terranes that have collided due to plate tectonic motions.

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Triassic

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The Period between 250 and 201 million years ago, named for a 3-fold rock division in Germany. Dinosaurs were developed during the second half of the Triassic as a minor family, which became much more prominent during the Jurassic and Cretaceous Periods

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Traprock

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The commercial name for basalt is trap, derived from a Swedish word for stairs or steps. The name is related to the step-like form of the eroded surface of some columnar basalt.