Tag Archives: Arkansas

Notes from the Field: Weathers and Delaney Quadrangles

 

Parthenon in Felkins Creek

Parthenon Sandstone overlying Brentwood Limestone on Felkins Creek, Weathers quadrangle

Recently, geologists at the Arkansas Geological Survey (AGS) completed geologic mapping of the Weathers and Delaney quadrangles in northwest Arkansas. These quadrangles are part of the U. S. Geological Survey’s 7.5-minute topographic series and cover an area of approximately 120 square miles. This project was made possible by a grant from the National Cooperative Geologic Mapping Program of which STATEMAP is a part. This year marks the 25th year of STATEMAP projects in Arkansas and represents an unprecedented commitment to gathering data on the geologic features of our State. STATEMAP was established in 1992 by an act of Congress to encourage the states to map their geology at the 1:24,000 scale. The first grant received by the Arkansas Geological Survey, then known as the Arkansas Geological Commission, was for a proposal in fiscal year 1994.  Since that time, eighty, 1:24,000-scale geologic maps have been completed, including the Weathers and Delaney quads.

Printed copies of the new geologic maps (and many others) are available at the AGS office in Little Rock for $12.50, but they are also available as a free download in .pdf form on our website. Here’s the link to the Delaney Quadrangle:

https://www.geology.arkansas.gov/docs/pdf/maps-and-data/geologic_maps/24k/Delaney.pdf

Geologic Map of Delaney Quadrangle

And here’s the link to the Weathers Quadrangle:

https://www.geology.arkansas.gov/docs/pdf/maps-and-data/geologic_maps/24k/Weathers.pdf

Geologic Map of Weathers Quadrangle

STATEMAP, which is administered by the U. S. Geological Survey, provides Arkansas with federal dollars through an annual grant proposal process. These funds are matched by the AGS which then performs all the work necessary to produce new geologic maps for the State. This year’s grant enabled the AGS to hire a geologist and to partially cover expenses incurred during field work. Garry Hatzell and staff geologist Richard Hutto worked together as a team during the data collection and map production phases of the project. This team approach has worked well for the AGS during its long history of geologic mapping, both for safety and efficiency.

The goal of STATEMAP is to classify bedrock exposed at the surface into recognizable units, such as formations and members, based on a common lithology—basically, an areal inventory of surface materials. Unfortunately, bedrock outcrops are few and far between in our State because so much of the surface is covered by alluvium (stream deposits) or colluvium (slope deposits). Since we are mapping the bedrock geology, we have to find ways to see through this cover and infer what is beneath it. We do map certain types of surficial deposits in some areas, however. Along the valleys of mature streams for instance, alluvium and terrace deposits are mapped. On steep hillsides, various types of debris flows considered to have moved in the recent past are mapped as landslides. Structural features, such as faults or folds, that offset or deform rock units are also described and mapped. In areas where the bedrock is covered, these relationships are inferred from data gathered nearby where outcrops are better.

Landslide in Atoka near Frog BayouParthenon Boulders in Kings River

Recent landslide in the Atoka Formation on the Delaney quad (left) and boulders of Parthenon sandstone in Kings River on the Weathers quad (right)

For this reason, much of our data collection efforts are concentrated on stream beds. There, erosional processes have typically removed soil and loose rock leaving sporadic, well-exposed outcrops of bedrock to study. Also, following a streambed allows us to see strata from bottom to top (or vice versa) which puts each formation in context with others. Locating and describing the physical contacts between formations is one of the most important things we do while mapping. Because formations are laterally extensive, disparate points taken on similar contacts can be connected across the mapping area to delineate each formation. Drawing these contact lines between formations in the correct location is a major focus of the mapping process.

Parthenon/Brentwood at Kings River FallsParthenon/Brentwood in Crosses Creek

Contact between the Parthenon and Brentwood Members of the Bloyd Formation on the Weathers quad at Kings River Falls (left) and on the Delaney quad in Crosses Creek (right)

Currently, the AGS’s STATEMAP projects are focused on the Ozark Plateaus Province, part of the Interior Highlands Physiographic Region located in the northern part of the State. The Ozark Plateaus in Arkansas consist of three broad surfaces that have developed due to differential erosion of Paleozoic sedimentary rocks on the southern flank of the Ozark Dome. Weathers and Delaney lie within the Boston Mountains Plateau, the southernmost and highest of these three surfaces. On these quads, over 1000 feet (305 meters) of Mississippian to Pennsylvanian (Chesterian, Morrowan, and Atokan) carbonate and clastic rocks are exposed. These rocks formed from sediment deposited in distal to near shore marine, tidal, deltaic, and fluvial environments.

Boston Mountains Plateau from Boston, Ark.

On the Boston Mountains Plateau, looking west toward Delaney from Boston.

In this area, the White River is increasingly being utilized as a public water source. Because of its importance in this regard, there is a lot of interest in gathering baseline data in this watershed. Most of the Delaney quad is drained by the White River, the uppermost reaches of the Middle Fork of the White River, and numerous smaller tributaries of the White. Some small drainages along the west side of the quad and Frog Bayou along the southern edge drain to the Arkansas River. Most of Weathers quad is drained by the Kings River and its tributaries as well as upper reaches of War Eagle Creek and the Buffalo River, all of which contribute to the White. Field work this year included hiking, wading, and swimming about 4.5 miles of the White River and 7 miles of the Middle Fork of the White River on the Delaney quad. 11 miles of the Kings River and 10.5 miles of Felkins Creek were traversed on the Weathers, along with numerous other streambeds on both quads.

Fossiliferous Brentwood in White RiverFossiliferous Brentwood in Cowcumber Creek

Close examination of fossiliferous Brentwood Limestone in White River on Delaney quad (left). Crinoid detritus including spines and cup plates in the Brentwood in Cowcumber Creek on Weathers quad (right)

The most significant structural feature on Weathers is the Russell Ridge Monocline, the axis of which is oriented parallel to other northeast-trending faults and lineations in northwest Arkansas. Presumably these align with regional faulting of Precambrian basement rock. The strata are depressed approximately 200 feet (61 meters) from southeast to northwest across this structure. Various normal faults with throws from 60-100 feet (18-20 meters) were also mapped. In the northwest corner of Delaney, the Drakes Creek Fault, a normal fault that also trends northeast, is downthrown to the southeast approximately 200 feet (61 meters).

Normal fault in Whispering Hollow

Yellow line marking the trace of a normal fault in Whispering Hollow on Weathers. Pitkin (Mp) downthrown to Fayetteville (Mf) approximately 60 feet (18 meters)

The Ozark National Forest occupies parts of the southern two thirds of Delaney and the southern third of Weathers. It is managed by the U. S. Forest Service. Along a reach of the Kings River in the southern part of Weathers is the Kings River Falls Natural Area which is maintained by the Arkansas Natural Heritage Commission.

Kings River Falls

Kings River Falls, the centerpiece of the 1059-acre Kings River Falls Natural Area

Field work commenced on July 16, 2018 and was finished on March 28, 2019 for a total of 75 days. From early April through the end of June, the geologists analyzed field data, classified rock specimens, and wrote descriptions specific to each quadrangle. Contacts and structural features were drawn on a topographic map base both digitally and by hand. Brian Kehner and Kerstein Dunn helped digitize and symbolize the map elements in ArcMap, developed alternative base maps, and integrated field data into our seamless geodatabase. Final layout of the maps was accomplished in Adobe Illustrator by Garry Hatzell, and they were edited by AGS geologic staff.

Prairie Grove in Kings RiverAtoka in Shrader Hollow

Massive calcareous sandstone in the Prairie Grove Member of the Hale Formation in Kings River on Weathers (left). Thin-bedded sandstone in the Atoka Formation in Shrader Branch on Delaney (right)

Special thanks to Ciara Mills for accompanying us in the field several weeks this year. Also to Angela Chandler for writing the proposal and serving as Principal Investigator again this year. Her guidance and support of geologic mapping in the State inspires us all to do great things. Very special thanks to Jerry and Joan Johnson of Madison County whose hospitality and knowledge of the people and places in the mapping area provided invaluable support for our endeavor this year.

Joan, Richard, and JerryAngela

Joan Johnson, Richard Hutto, and Jerry Johnson by Little Mulberry Creek (left) and Angela Chandler on North Sylamore Creek (right)

Next year, STATEMAP is heading farther north to the Salem Plateau where Scott Ausbrooks, Bill Prior, and Garry Hatzell will be mapping the Mammoth Springs quadrangle. So if you see someone up there taking an unusually keen interest in the rocks, be sure to say hello.

Until next time, I’ll see you in the field!

Richard Hutto

 Team Ozark

Garry Hatzell and Richard Hutto—out standing in the field

Geo-pic of the week: A lively sea in North Arkansas

 

Starfish pit 2Starfish pit 1

Starfish pit 4Starfish pit 6

Starfish pit 5Starfish pit 3     

The above pictures are of sandstone beds from a quarry in North Arkansas developed in a rock formation called the Batesville Sandstone.  Though it formed in a marine setting, the Batesville is typically composed of fairly homogeneous, flat-bedded rock with little evidence of inhabitation.  This spot is an exception.  The pictures clearly indicate the depositional environment was teaming with sea life at the time the sediment was emplaced.  

The abundant trace fossils, which preserve the activity of organisms rather than their physical form, show a variety of behaviors common to marine invertebrate animals that lived in Arkansas more than 330 million years ago.  Remnants of grazing traces of various snail and worm-like critters (A), resting traces (starfish; B), Dwelling burrows (sea-anemone or bivalve?; C), and locomotion trails (D) are indicators of the conditions present in North Arkansas near the end of Mississippian time.   

Geo-pic of the week: Aerial Photography

Aerial Photo-Central Arkansas

Sometimes the best way to see what’s on the ground is to get as far away from it as possible.  Geologists use a variety of tools to do just that.  One of those tools is aerial photography.

The picture above shows the Arkansas River where it leaves the mountainous western uplands and enters the bottomlands of the Mississippi Alluvial Plain, east of Little Rock (upper left).  Driving east across that boundary, it’s easy to get the impression that the Mississippi Alluvial Plain is a broad flat expanse of land with little to no distinguishing features.  That’s far from the case as this photo reveals.  

From high-altitude imagery, subtle relic features created by the Arkansas River can be easily recognized.  Note the swirling landforms that characterize the lowlands on the right side of the picture.  Over time the Arkansas River has meandered through the valley carving new channel courses and abandoning old reaches of channel.  The continually changing river has left a mosaic of oxbow lakes (water-filled abandoned channels) and arc-shaped river deposits known as point bars. 

Geo-pic of the week: Cleavage

clip_image002Calcite at atomic resolution

The mineral in the above pictures is calcite, a common mineral in earth’s crust that is the main component of the sedimentary rock limestone.  The stack of samples (top) exhibit a physical characteristic known as cleavage.  The cleavage of calcite causes it to break into a rhombus-shape (see picture).

Cleavage is the tendency of a crystalline substance, such as a mineral, to break along parallel planes that reflect the internal arrangement of the atoms in the crystal.  All crystals, by definition, have a uniform atomic arrangement.  To illustrate this property, I’ve included a second picture (bottom), borrowed from Dr. Cathy Sutton, that shows an extremely magnified calcite crystal.  The repeating rhombus-shapes in the picture are individual calcite molecules.  Basically, cleavage is the outward expression of the internal structure of a mineral.

The samples on the left were collected from Midwest Lime Quarry, Batesville, Arkansas.

Geo-pic of the week: Trilobite Romance

trilobite meeting in pennsylvanian

The photo above shows trace fossils that record the travels of two trilobites.  Trilobites are an extinct group of marine invertebrate animals, resembling horse-shoe crabs, that flourished for 100s of millions of years in the Paleozoic Era (540-250 mya).   The tracks the animal left are known as the trace fossil, Cruziana.  It appears that one traveled from the right side of the photo, the other from the left, until they met in the middle where they rested for a while.  At the center of the photo are resting traces known as Rusophycus.  Perhaps they became friends or maybe they were even more than friends?  It is Valentine’s Day.  Their traces are preserved in the Atoka Formation of west-central Arkansas.  

2019 STATEMAP Field Calendar now available for download

Download a commemorative 25th anniversary STATEMAP Field Calendar here:

https://www.geology.arkansas.gov/publication/other-publications/statemap-field-calendar-2019.html

We are celebrating the 25th year of detailed geologic mapping in Arkansas made possible by the passage of the National Geologic Mapping Act of 1992. It established STATEMAP which distributes funds to the states, typically geological surveys, in the form of cooperative grants which are used to partially fund various geologic mapping projects. The first grant received by the Arkansas Geological Survey, then known as the Arkansas Geological Commission, was for a proposal in fiscal year 1994.  Since that time, seventy-eight 1:24,000-scale geologic maps have been completed, with two more on the way this year.  Two maps at the 1:100,000-scale have also been published.  This marks an unprecedented commitment to gathering data about the surface of the earth in our state. Following is a factsheet summarizing the STATEMAP projects in Arkansas since 1994.

Statemap Factsheet-front-2019

Here is the law establishing STATEMAP:

National Geologic Mapping Act of 1992

PUBLIC LAW 102-285

102d Congress

signed May 18, 1992

 

An Act

To enhance geologic mapping of the United States, and for other purposes.

 

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled,

 

43 USC section 31a. Findings and purpose

(a) Findings

 The Congress finds and declares that–

(1) during the past 2 decades, the production of geologic maps has been drastically curtailed;

(2) geologic maps are the primary data base for virtually all applied and basic earth-science applications, including–

(A) exploration for and development of mineral, energy, and water resources:

(B) screening and characterizing sites for toxic and nuclear waste disposal;

(C) land use evaluation and planning for environmental protection;

(D) earthquake hazards reduction;

(E) predicting volcanic hazards;

(F) design and construction of infrastructure requirements such as utility lifelines, transportation corridors, and surface-water impoundments;

(G) reducing losses from landslides and other ground failures;

(H) mitigating effects of coastal and stream erosion;

(I) siting of critical facilities; and

(J) basic earth-science research;

(3) Federal agencies, State and local governments, private industry, and the general public depend on the information provided by geologic maps to determine the extent of potential environmental damage before embarking on projects that could lead to preventable, costly environmental problems or litigation;

(4) the combined capabilities of State, Federal, and academic groups to provide geologic mapping are not sufficient to meet the present and future needs of the United States for national security, environmental protection, and energy self-sufficiency of the Nation;

(5) States are willing to contribute 50 percent of the funding necessary to complete the mapping of the geology within the State;

(6) the lack of proper geologic maps has led to the poor design of such structures as dams and waste-disposal facilities;

(7) geologic maps have proven indispensable in the search for needed fossil-fuel and mineral resources; and

(8) a comprehensive nationwide program of geologic mapping is required in order to systematically build the Nation’s geologic-map data base at a pace that responds to increasing demand.

 

(b) Purpose

The purpose of sections 31a to 31h of this title is to expedite the production of a geologic-map data base for the Nation, to be located within the United States Geological Survey, which can be applied to land-use management, assessment, and utilization, conservation of natural resources, groundwater management, and environmental protection.

 

section 31c. Geologic mapping program

 

(c) Program objectives

The objectives of the geologic mapping program shall include–

(1) determining the Nation’s geologic framework through systematic development of geologic maps at scales appropriate to the geologic setting and the perceived applications, such maps to be contributed to the national geologic map data base;

(2) development of a complementary national geophysical-map data base, geochemical-map data base, and a geochronologic and paleontologic data base that provide value-added descriptive and interpretive information to the geologic-map data base;

(3) application of cost-effective mapping techniques that assemble, produce, translate and disseminate geologic-map information and that render such information of greater application and benefit to the public; and

(4) development of public awareness for the role and application of geologic-map information to the resolution of national issues of land use management.

(d) Program components

(3) A State geologic mapping component, whose objective shall be determining the geologic framework of areas that the State geological surveys determine to be vital to the economic, social, or scientific welfare of individual States. Mapping priorities shall be determined by multirepresentational State panels and shall be integrated with national priorities. Federal funding for the State component shall be matched on a one-to-one basis with non-Federal funds.

Miss January

https://www.geology.arkansas.gov/publication/other-publications/statemap-field-calendar-2019.html

Geo-pic of the week: Sand and clay of the Wilcox Group

wilcox sand canyon pit enhanced

This rather handsome outcrop of the Wilcox group consists of alternating layers of sand and clay of the Eocene Epoch which lasted from about 56-34 million years ago.   The Wilcox Group is a non-marine unit mostly composed of sand with lesser clay, silt, gravel, and lignite (low-grade coal).  

This geologic unit is part of a larger sequence of loosely-consolidated sedimentary rocks exposed in south central Arkansas, south of Pulaski county.  These rocks are the northern extent of the West Gulf Coastal Plain, a physiographic province that stretches from central Arkansas, south, to the Gulf of Mexico.