North Dakota Geology

Geology and Time

• Geology and time are closely related, with layers of sediment capturing changes in climate, water levels, and life over billions of years.
• These changes shaped North Dakota's modern landscape and economy.

Divisions of Geological Time

• Geological time is divided into eras, periods, and epochs, with eras being the largest periods.
• Eras are made up of several periods, which are subdivided into epochs.
• Epochs are made up of formations, which are measured by layers of rock buried deep under the surface.

Eras and Stratigraphic Columns

• There are four eras characterized by geological changes brought about by wind, water, earthquakes, or volcanoes, and the development of plant and animal life.
• Stratigraphic columns show the eras and cover the Earth's history, including North Dakota's 600 million-year history.

North Dakota's Geological Record

• The Paleozoic Era began about 570 million years ago, with seas flowing and draining, forming the Williston Basin.
• Life expanded, evolved, and became extinct during this era.
• The Mesozoic Era and Cenozoic Era saw the dominance of mammals and grasses, with climate changes leading to the current pattern of cold winters and warm summers.

Paleontological Research

• Geologists and paleontologists read the layers to learn about the landscape and non-human life forms.
• Knowledge is based on 200 years of scientific research and is continually evolving with new discoveries.

Special Terms

• BPE (Before the Present Era) is used to denote time before the present, especially for events that occurred millions of years ago.
• Core samples are cylindrical slices of Earth's layers obtained by drilling below the surface.
• Coteau refers to an area east of the Missouri River characterized by small lakes and ponds formed by glaciers.
• Dinosaurs were extinct reptiles from the Mesozoic Era, some walking upright on two legs and others on four.
• Erratics are large rocks left on North Dakota prairies by glaciers, too heavy to be moved by water or wind.
• Esker refers to a ridge formed by gravel and sand deposited by streams flowing under or through glaciers.
• Extinction refers to the complete disappearance of a species from Earth, either globally or in a specific region.
• Formation refers to a distinct layer of rock visible in cliffs or river banks, named after nearby permanent features.
• Geologist refers to a scientist who studies Earth's rocks, minerals, and geological processes.
• Glacier refers to a large mass of ice formed from compacted snow that moves slowly and reshapes the land underneath it.
• Glacial till refers to sediment left behind as glaciers retreat, varying in size from clay particles to boulders.
• Iridium is a rare mineral found abundantly in asteroids and meteors, associated with the K-T boundary layer linked to dinosaur extinction.
• K-T Boundary refers to the geological boundary marking the end of the Cretaceous Period and the start of the Tertiary Period, associated with mass extinctions, including dinosaurs.
• Lake Agassiz refers to a large freshwater lake formed during the Ice Age, leaving behind sediment that shaped the Red River valley.
• Lignite refers to a type of coal found in North Dakota, lower in heat production compared to other types of coal.
• Mammals refer to animals that give birth to live young and nurse them with milk until they can feed themselves.
• Moraine refers to a hill of gravel or rock deposited by a melting glacier.
• Paleontologist refers to a scientist who studies fossilized plants and animals from ancient times.
• Sediment refers to material deposited by wind, water, or ice.
• Sedimentary rock refers to rock formed from compressed layers of sediment over geological time.
• Strata refer to layers of sediment or rock beneath Earth's surface.
• Stratigraphy refers to the study and visualization of geological layers and their relationships.

Formations

• Formations are layers of sand, silt, rock, and other substances laid down in North Dakota over millions of years.
• Each layer has a name, which represents a time period, and its own story, including origins, conditions, and contents.
• Stratigraphic charts are used to view the orders of stratigraphy.

The Williston Basin

• The Williston Basin is a geographical area covering parts of Saskatchewan, Manitoba, Montana, South Dakota, and North Dakota.
• The basin is characterized by sedimentary layers, with a depth of over 16,000 feet near the center.
• The area is a major source of coal, oil, and natural gas.

Petroleum Formation

• Petroleum formation occurred when plankton and microscopic organisms in inland seas died and fell to the sea floor.
• The organisms were covered by sediments over millions of years, creating pressure and heat, and transforming into oil and gas.

The Missouri and the Red River

• North Dakota's rivers are youthful in geological terms, with shallow river beds prone to flooding.
• Historical flow directions include the pre-glaciation path of the Missouri River and the current flow of the Red River.
• The Missouri River's path was changed by glaciers, which redirected the river southward.

Glaciation Events

• Glaciation events refer to periods when ice advanced from polar caps to usually warmer lands.
• The last ice age occurred from 2.6 million years ago, with multiple glaciation periods during the Pleistocene Epoch.
• Glaciers were thousands of feet thick, composed of half ice and half debris.
• Debris included rocks, gravel, and sand carried and deposited by glaciers, forming glacial till.

Types of Glacial Deposits

• Erratics refer to individual rocks left behind by glaciers.
• Moraines refer to hills of sand, gravel, and rocks left by glaciers.
• Eskers refer to ridges formed by sediment carried beneath glaciers' meltwater rivers.

Last Ice Age in North Dakota

• The last ice age in North Dakota occurred from 25,000 to 12,000 years ago, with ice sheets up to 400 feet thick covering three-fourths of the state.
• The glaciers created rolling hills and formed Glacial Lake Agassiz, which covered 110,000 square miles.

Plants and Animals

• Early geological history: North Dakota was submerged under water with tiny one-celled aquatic plants.
• Tropical plants like palm trees, giant redwoods, and ferns formed dense forests during warm periods.
• The transition to grasslands occurred due to semi-arid climate and grazing animals.
• Geological epochs and plant evolution: the Late Cretaceous Period, Eocene Epoch, Oligocene Epoch, and Miocene Epoch saw the evolution of different plant species.
• Fossil record and grassland formation: the Miocene Epoch saw the debate among scientists about the origin of North Dakota's grasslands.
• Post-glacial changes: the climate became drier, leading to the spread of modern grasses like Big Bluestem and prairie flowers.

Soil

• Formation of soil: soil develops from rocks over millions of years, influenced by weathering and plant roots.
• Components of soil: soil is a mixture of sand, silt, and clay, with organic matter making up 5% of soil.
• Effect of climate on soil: climate influences plant growth, which in turn impacts soil composition.
• Characteristics of grassland soil: grasses contribute more nutrients back to the soil, enhancing fertility.
• Soil horizons: soil scientists study soil horizons to understand soil characteristics and fertility.

Animals

• Ancient fauna and evolution: North Dakota hosted diverse microscopic organisms in warm seas, and vertebrates with backbones evolved, including dinosaurs, lizards, and mammals.

• The impact of the K-T boundary: the asteroid impact theory explains the mass extinction at the K-T boundary, but ongoing research considers other factors.

• Animals of the Late Cretaceous Period: marine life included small creatures like clams, corals, urchins, and lobsters, and larger predators like the Plioplatecarpus or mosasaur, and the flightless bird Hesperornis regalis.### Dinosaurs and Flying Reptiles

• Massive carnivore, Tyrannosaurus rex, up to 40 feet long and 20 feet tall, with a five-foot-long head and immense bite force.

• Known predator of Edmontosaurs and Triceratops, debated as a predator or scavenger.

• Flying reptiles like Pteranodon inhabited the skies, with a wingspan of 20 feet, primarily feeding on fish.

Impact of the K-T Boundary

• Extinction event around 65 million years ago marked the end of dinosaurs and dominance of reptiles.
• The rise of mammals followed, shaping the future fauna diversity.

Eocene Epoch (55 to 34 million years ago)

• North Dakota experienced tropical conditions with dense forests.
• Diverse fauna included:
  • Coryphodon: Hippopotamus-like, swamp-dwelling mammal.
  • Eohippus (Hyracotherium): Early horse ancestor, small with multiple toes.
• Global cooling marked the end of the Eocene Epoch.

Oligocene Epoch (33 to 23 million years ago)

• North Dakota transitioned into a treeless plain with shrubs and grasses.
• Major fauna included:
  • Thunder Beast (Brontops): Large, intimidating plant-eater with bony snout projections.
  • Mesohippus: Descendant of Eohippus, larger than its predecessor, adapted to browsing leaves.
  • Poebrotherium: Early camel ancestor, lacked humps, similar in size to a goat.
  • Leptomeryx: Small, antler-less, fast-running deer-like animal.
  • Saber-toothed cats (Dinictus): Predatory with long, serrated canine teeth.
  • Rabbits (Palaeolagus), tortoises (Stylemys), sweat bees (Celliforma species), and rodents (Eumys species) were also common.

Animals of the Pleistocene Epoch

• Woolly Mammoths (Mammuthus primigenius)
  • Originated from Asia via the Bering Land Bridge.
  • Reached up to nine feet at the shoulder.
  • Ate grass, roots, and tree bark using their tusks and trunk.
  • Had heavy, dark brown coats with a fine undercoat for warmth.
  • Became extinct about 10,000 years ago, coinciding with human presence in North Dakota.
• Mastodons (Mammut americanum)
  • Evolved in North America over millions of years.
  • About 10 feet tall at the shoulder.
  • Used tusks to tear bark from trees; preferred browsing leaves and bark.
  • Had long, dark, thick hair coats with a fine undercoat.
  • Lived in boggy areas and became extinct about 10,000 years ago.
• Bison latifrons
  • Ancestor of modern bison, larger than today's species.
  • Had horns measuring seven feet from tip to tip.
  • Lived in small herds and preferred woodland habitats.
• Ice Age Horses (Equus)
  • Resembled modern horses with a single toe and hard hoof.
  • Larger than their ancestors; grazers dependent on grass.
  • Became extinct in North Dakota and North America by the end of the Ice Age.
• Saber-Toothed Cat (Smilodon fatalis)
  • Fearsome predator, slightly smaller than a modern lion but heavier.
  • Had powerful front legs and seven-inch-long canine teeth.
  • Used strong jaws to bite into prey's skull, sometimes breaking their canines.
  • Extinct by the end of the Ice Age.

Extinction and Causes

• Larger Ice Age mammals like mastodons and horses became extinct.
• Smaller to medium-sized animals like deer survived.
• Factors contributing to extinction may include climate change and human hunting.

The Paleontology Laboratory

• Role of Paleontologists
  • Study fossils to reconstruct ancient ecosystems and understand evolutionary history.
  • Carefully document fossil locations and geological layers to date and contextualize fossils.
  • Protect fragile fossils with plaster jackets during excavation to preserve their integrity.
• North Dakota's Paleontology Laboratory
  • Housed within the State Historical Society, it holds thousands of fossil specimens.
  • Fossils include bones, teeth, and fossilized plants captured in rock formations.
  • The laboratory is essential for cleaning, identifying, and cataloging fossils.
• Excavation and Preservation
  • Fossils are excavated from rock formations and meticulously cleaned in the laboratory.
  • Analyze bones for identifying features like spinal processes and tooth structures.
  • Fragile fossils may require reconstruction or replication for display to protect the originals.
• Common Fossil Finds in North Dakota
  • Edmontosaurus and Triceratops fossils are relatively common.
  • Tyrannosaurus rex remains are rarer due to fewer discoveries.
  • Fossils from the Oligocene Epoch are scarcer due to high erosion rates.
• Displaying Fossils
  • Fragile or incomplete fossils are reconstructed or replicated for museum displays.
  • Techniques include sculpting missing parts, creating molds, or crafting replicas from lightweight materials.
  • Original fossils are preserved while replicas are used for educational and exhibition purposes.