The flat-lying sedimentary strata of the North American midcontinent are typically thought of as uniform and predictable. However, midcontinent geology contains a record of exciting geologic events and processes. The papers in this volume examine four geologic phenomena associated with the continental interior: Pennsylvanian and Permian cyclothems, the origin of a massive Permian salt deposit, Cretaceous kimberlite intrusions, and Quaternary glacial geology. The guides cover processes and events that are unique to the geology of Kansas and highlight important economic and rich historical influences of these geologic features.

ABSTRACT This field guide covers a half-day tour of three localities representative of the Cretaceous kimberlites of Riley and Marshall Counties in northeastern Kansas: Stockdale, Bala, and Winkler Crater. The kimberlites are porphyritic with phenocrysts of olivine and smaller amounts of pyroxene, magnetite, ilmenite, pyrope garnet, and/or phlogopite. Most of the kimberlites include abundant shallow crustal xenoliths of altered shale or sedimentary carbonate; igneous and metamorphic xenoliths from the lower crust and upper mantle occur but are less common. The kimberlites can be divided into two types, micaceous and non-micaceous. Examples of both kimberlite types will be examined during the field trip—Stockdale and Winkler Crater are micaceous kimberlites, whereas Bala is non-micaceous. The existence of kimberlites in the midcontinent of North America has long been controversial. In Kansas, they erupted through Proterozoic (1.8–1.6 Ga) basement that was accreted to the southeastern margin of North America, raising the question of how the conditions for kimberlitic melt genesis can be met so far from thick Archean craton (e.g., thick lithosphere >200 km where volatile and trace element–enriched melts can form and accumulate). However, recent geophysical data indicate that the kimberlites were generated within the boundary between thick Proterozoic lithosphere to the east, where depth to the lithosphere-asthenosphere boundary (LAB) is at least 200 km, and regions to the west where the LAB is <190 km as thick cratonic lithosphere thins into Mesozoic extensional basins. New ground gravity data show that the kimberlite pipes are oriented in a NE–SW direction, parallel to the Precambrian Midcontinent rift, which occurs in the subsurface west of the kimberlite field. The data indicate that the kimberlites took advantage of preexisting structural weaknesses that were reactivated in the Cretaceous.

ABSTRACT The Midcontinent Permian succession in Kansas shows a long-term trend from a monsoonal to semi-arid climate (early Permian) to an increasingly arid and evaporitic climate (late Permian), superimposed by higher-frequency variations that resulted in the alternating deposition of marine carbonates, shales, and paleosols. Within the high-frequency cycles, at least three different orders of subcycles can be recognized: (1) the cyclothems, interpreted as representing glacio-eustatic sea-level fluctuations driven by Milankovitch orbital modulations; (2) the carbonate-to-clastic facies patterns, interpreted as climate change from arid to monsoonal; and (3) the calcic to vertic paleosol profiles, possibly a reflection of increasing precipitation within a monsoonal regime, controlled by weak versus strong monsoons. This field trip focuses on the Lower Permian (Wolfcampian) succession exposed in the Manhattan area, Riley County, Kansas. Nearly continuous exposures display numerous cycles of sea-level change (“cyclothems”). Stacked paleosol horizons that are part of the Wolfcampian cyclothems also record climate changes, from arid/semi-arid to sub-humid/seasonal climates.

ABSTRACT The 120-m-thick Hutchinson Salt Member of the Permian Wellington Formation of central Kansas supports multiple industries. Composed of bedded halite, gypsum/anhydrite, and minor siliciclastic mudstone, it was deposited by shallow saline waters in a warm, dry climate. Underground salt mines access the purest horizon, producing salt that is distributed through the United States and Canada. The vast space left by mining supports a prosperous commercial storage enterprise and a popular underground tourist attraction. Vertical solution-mined caverns host the nation’s primary midcontinent liquid petroleum gas storage industry. This field trip will explore the origin and use of the Hutchinson Salt in core samples and subsurface outcrops while meeting in an underground salt cavern, and above ground at a solution-mined storage cavern.

ABSTRACT The Kansas City metropolitan region is a key geographic point in the exploration, settlement, and development of the United States. Several major pre-industrial trails originated from this vicinity, and the most important Civil War conflict west of the Mississippi, the Battle of Westport, took place here. Bedrock geology consists of Upper Pennsylvanian cyclothems that represent repeated marine transgressions and regressions over a shallow continental shelf and lowland. The modern landscape was shaped largely as a result of Pleistocene glaciation and related glacial meltwater drainage.

Abstract Route 66 is among the most famous American highways of the middle twentieth century. A portion of the original Route 66 runs through southwestern Missouri, southeastern Kansas, and northeastern Oklahoma. This section of the road was intimately linked to the Tri-state region’s economic geology, namely mining lead and zinc as well as producing the fossil fuels—coal and natural gas—to smelt the ore. Mining began in the Tri-state district in the mid-nineteenth century and continued into the late twentieth century. An economic boom led to regional population growth and contributed to national development, but no environmental regulations existed during this period. The legacy of mining includes severe pollution, ruined communities, serious human-health issues, and devastated landscapes. Efforts now focus on protecting human health, reclamation of mined land, and remediation of water resources, led by federal and state agencies as well as universities and non-governmental organizations.

Abstract The 2.4-km-long Proffit Mountain flood scour formed when the upper reservoir of the Taum Sauk Power Plant, a reversible pumped electric storage facility, failed on 14 December 2005. Approximately 1.3 billion gallons of water drained from the reservoir in roughly 12 minutes, scouring a small tributary on the west flank of Proffit Mountain to bedrock and depositing debris in the valley floor and in the valley of the East Fork of the Black River. The stratigraphic succession exposed includes Mesoproterozoic Taum Sauk Rhyolite and Munger Granite, Cambrian conglomerate and dolomite and flood deposits. The site provides a unique opportunity to study a landscape-scale outcrop.

Abstract Riverbluff Cave developed near the southern margin of the Springfield Plateau as a single passage between James River and its tributary, Ward Branch. Portions of the cave preserve a general fining-upward sediment sequence, but with highly fossiliferous gravel beds near the middle. These gravel beds include fragments of various vertebrates, including mammoth and horse. Trackways and claw marks are also preserved atop the sediment in numerous locations. Cosmogenic isotope data provide burial dates for some of the sediment layers and fossil remains. The earliest sediment (reverse magnetic polarity) entered the cave at ~1.1 Ma, while the fossiliferous gravel bed is dated at ~0.74 Ma. The overlying laminated silts and clays have normal polarity with a burial date of ~0.65 Ma at the base. Thus, the sediment sequence spans the Matuyama/Brunhes paleomagnetic datum, and records at least 450 ka of sedimentation within the cave.

Abstract This field trip provides an overview of geological features in southwestern Missouri that are related to the American Civil War and to human culture. This includes the geology and history of the Wilson’s Creek National Battlefield (where the second important battle of the American Civil War was fought on 10 August 1861), Zágonyi’s Charge (25 October 1861), the Battle of Springfield (8 January 1863), and the gravestones and monuments of the National Cemetery in Springfield in which many of those who fought at Wilson’s Creek and other Civil War conflicts are buried. Other stops include the Springfield Underground and the quarries and facilities at what was once the town of Phenix (which, along with Carthage, Missouri, was the home of some of the largest dimension-stone quarries west of the Mississippi River); and a reconstructed mill site in Point Lookout, just south of Branson. Most of the field trip involves outcrops, quarries, and bedrock composed of the Mississippian Burlington-Keokuk limestones (undivided), providing numerous chances to examine outcrops and products made of limestone and chert.

Abstract Climate and terrain, especially stream drainage basins and topography, greatly influenced European-American settlement patterns, agricultural practices, transportation networks, and the cultural and economic development of the southern Missouri Ozarks from the early 1800s to the American Civil War (1861-1865). These also were key factors, together with land cover and natural resources, that predicated the course of military operations and tactics during the war. The same factors affected widespread partisan conflicts during the war and vigilantism during the Bald Knob-ber era, a mid-1880s cultural extension of the Civil War in Taney, Christian, Douglas, and Stone counties. This field trip will examine the geology of selected areas in and around Branson in southwestern Taney County and integrate historical events and anecdotes, which illustrate the influence of geologic factors.

Abstract This field trip examines the geology and geohydrology of a dissected part of the Salem Plateau in the Ozark Plateaus province of south-central Missouri. Rocks exposed in this area include karstified, flat-lying, lower Paleozoic carbonate platform rocks deposited on Mesoproterozoic basement. The latter is exposed as an uplift located about 40 mi southwest of the St. Francois Mountains and form the core of the Ozark dome. On day 1, participants will examine and explore major karst features developed in Paleozoic carbonate strata on the Current River; this will include Devil’s Well and Round Spring Cavern as well as Montauk, Round, Alley, and Big Springs. The average discharge of the latter is 276 × 10 6 gpd and is rated in the top 20 springs in the world. Another, Alley Spring, is equally spectacular with an average discharge of 81 × 10 6 gpd. Both are major contributors to the Current and Eleven Point River drainage system which includes about 50 Mesoproterozoic volcanic knobs and two granite outcrops. These knobs are mainly caldera-erupted ignimbrites with a total thickness of 7–8 km. They are overlain by post-collapse lavas and intruded by domes dated at 1470 Ma. Volcaniclastic sediment and air-fall lapilli tuff are widely distributed along this synvolcanic unconformity. On day 2, the group will examine the most important volcanic features and the southernmost granite exposure in Missouri. The trip concludes with a discussion of the Missouri Gravity Low, the Eminence caldera, and the volcanic history of southern Missouri as well as a discussion of geologic controls on regional groundwater flow through this part of the Ozark aquifer.

Abstract Despite a long history of geologic investigations in the Ozarks, new studies and analyses continue to elucidate our understanding of the complex interconnection between the basement, extensive carbonate platforms, structural overprinting, mineralization, karstification, and hydrology. This guidebook volume highlights a few of these aspects as well as the connection to culture, history, and economic development of the Ozarks region.

Full article available in PDF version.

Abstract The Great Plains physiographic province lies east of the Rocky Mountains and extends from southern Alberta and Saskatchewan nearly to the United States-Mexico border. This chapter covers only the northern part of the unglaciated portion of this huge region, from Oklahoma almost to the United States-Canada border, a portion that herein will be referred to simply as the Northern Great Plains (Fig. 1). This region is in the rain shadow of the Rocky Mountains. Isoheyets are roughly longitudinal, and mean annual precipitation decreases from about 750 mm at the southeastern margin to less than 380 mm in the western and northern parts (Fig. 2). Winters typically are cold with relatively little precipitation, mostly as snow; summers are hot with increased precipitation, chiefly associated with movement of Pacific and Arctic air masses into warm, humid air masses from the Gulf of Mexico. Vegetation is almost wholly prairie grassland, due to the semiarid, markedly seasonal climate. The Northern Great Plains is a large region of generally low relief sloping eastward from the Rocky Mountains toward the Missouri and Mississippi Rivers. Its basic bedrock structure is a broad syncline, punctuated by the Black Hills and a few smaller uplifts, and by structural basins such as the Williston, Powder River, and Denver-Julesburg Basins (Fig. 3). Its “surface” bedrock is chiefly Cretaceous and Tertiary sediments, with small areas of older rocks in the Black Hills, central Montana, and eastern parts of Wyoming, Kansas, and Oklahoma. During the Laramide orogeny.

Abstract A series of long-studied exposures of glacial sediments is found immediately west of the city of Atchison, Atchison County, Kansas, along the south side of White Clay Creek in Sec. 2, 10, 1l, T.6S., R.20E. (Fig. 1). The stream cuts are readily accessible by foot from U.S. 59, which parallels the north side of White Clay Creek. It is advisable to ask local residents for permission to cross private property to reach the stream cuts.