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M. Dennis Krohn

Publications and source records attributed to M. Dennis Krohn.

17 recordsLinked to original sources
USGS2020

Repurposing a hindcast simulation of the 1926 Great Miami Hurricane, south Florida

Hydrodynamic model hindcasts of the surface water and groundwater of the Everglades and the greater Miami, Florida, area were used to simulate hydrology using estimated storm surge height, wind field, and rainfall for the Great Miami Hurricane (GMH), which struck on September 18, 1926. Ranked estimates of losses from hurricanes in inflation-adjusted dollars indicate that the GMH was one of the most damaging tropical cyclones to make landfall in the United States, but little hydrologic data were collected because many types of field stations did not exist at the time. Several techniques were used to estimate previously unknown critical storm variables for model input, demonstrating the value of reanalyzing historical storm events using modern hydrodynamic modeling. This representation of the 1926 GMH was then used to develop a hypothetical simulation of the hydrologic effects of a similar hurricane occurring in contemporary (1996) times. Results indicate that the 18-centimeter sea-level rise between 1926 and 1996 had a greater effect on salinity intrusion than climatic differences or the development of modern canal-based infrastructure. Moreover, the post-1926 canal infrastructure does not seem to substantially mitigate the deleterious effects of sea-level rise.

Florida↗
USGS2016

Post-Hurricane Ike coastal oblique aerial photographs collected along the Alabama, Mississippi, and Louisiana barrier islands and the north Texas coast, September 14-15, 2008

The U.S. Geological Survey (USGS), as part of the National Assessment of Coastal Change Hazards project, conducts baseline and storm-response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms (Morgan, 2009). On September 14-15, 2008, the USGS conducted an oblique aerial photographic survey along the Alabama, Mississippi, and Louisiana barrier islands and the north Texas coast, aboard a Beechcraft Super King Air 200 (aircraft) at an altitude of 500 feet (ft) and approximately 1,200 ft offshore. This mission was flown to collect post-Hurricane Ike data for assessing incremental changes in the beach and nearshore area since the last survey, flown on September 9-10, 2008, and the data can be used in the assessment of future coastal change. The photographs provided in this report are Joint Photographic Experts Group (JPEG) images. ExifTool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. The photograph locations are an estimate of the position of the aircraft at the time the photograph was taken and do not indicate the location of any feature in the images (see the Navigation Data page). These photographs document the state of the barrier islands and other coastal features at the time of the survey. Pages containing thumbnail images of the photographs, referred to as contact sheets, were created in 5-minute segments of flight time. These segments can be found on the Photos and Maps page. Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML file was created using the photographic navigation files. The KML file can be found in the kml folder.

Alabama, Louisiana, Mississippi, Texas↗
USGS2016

Post-Hurricane Irene coastal oblique aerial photographs collected from Ocracoke Inlet, North Carolina, to Virginia Beach, Virginia, August 30-31, 2011

The U.S. Geological Survey (USGS), as part of the National Assessment of Coastal Change Hazards project, conducts baseline and storm-response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms (Morgan, 2009). On August 30-31, 2011, the USGS conducted an oblique aerial photographic survey from Ocracoke Inlet, North Carolina, to Virginia Beach, Virginia, aboard a Piper Navajo Chieftain (aircraft) at an altitude of 500 feet (ft) and approximately 1,200 ft offshore. This mission was flown to collect post-Hurricane Irene data for assessing incremental changes in the beach and nearshore area since the last survey, flown in May 2008, and the data can be used in the assessment of future coastal change. The photographs provided in this report are Joint Photographic Experts Group (JPEG) images. ExifTool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. The photograph locations are an estimate of the position of the aircraft at the time the photograph was taken and do not indicate the location of any feature in the images (see the Navigation Data page). These photographs document the state of the barrier islands and other coastal features at the time of the survey. Pages containing thumbnail images of the photographs, referred to as contact sheets, were created in 5-minute segments of flight time. These segments can be found on the Photos and Maps page. Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. Table 1 provides detailed information about the GPS location, image name, date, and time for each of the 2,688 photographs that were taken along with links to each photograph. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML also shows the track of Hurricane Irene. The KML files were created using the photographic navigation files. These KML file(s) can be found in the kml folder.

North Carolina, Virginia↗
USGS2015

Numerical computation of hurricane effects on historic coastal hydrology in Southern Florida

Introduction Numerical models are critical for assessing the effects of sea level rise (SLR), hurricanes, and storm surge on vegetation change in the Everglades National Park. The model must be capable of representing short-timescale hydrodynamics, salinity transport, and groundwater interaction. However, there is also a strong need to adapt these numerical models to hindcast past conditions in order to examine long-term effects on the distribution of vegetation that cannot be determined using only the modern record. Methods Based on parameters developed for a numerical model developed for the recent 1996 to 2004 period, a hindcast model was developed to represent sea level and water management for the period of 1926 to 1932, constrained by the limited hydrology and meteorology data available from the historic past. Realistic hurricane-wind and storm surge representations, required for the hindcast model, are based on information synthesized from modern storm data. A series of simulation scenarios with various hurricane representations inserted into both hindcast and recent numerical models were used to assess the utility of the storm representation in the model and compare the two simulations. Results The comparison of the hindcast and recent models showed differences in the hydrology patterns that are consistent with known differences in water delivery systems and sea level rise. A 30x lower-resolution spatially variable wind grid for the hindcast produced similar results to the original high-resolution full wind grid representation of the recent simulation. Storm effects on hydrologic patterns demonstrated with the simulations show hydrologic processes that could have a long-term effect on vegetation change. Conclusions The hindcast simulation estimated hydrologic processes for the 1926 to 1932 period. It shows promise as a simulator in long-term ecological studies to test hypotheses based on theoretical or empirical-based studies at larger landscape scales.

Florida↗
USGS2015

Post-Nor'Ida coastal oblique aerial photographs collected from Ocean City, Maryland, to Hatteras, North Carolina, December 4, 2009

The U.S. Geological Survey (USGS) conducts baseline and storm response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms. The remnants of Tropical Storm Ida intensified to become a nor'easter (herein referred to as Nor'Ida). On December 4, 2009, the USGS conducted an oblique aerial photographic survey from Ocean City, Maryland, to Hatteras, North Carolina, aboard a U.S. Coast Guard HH60 helicopter at an altitude of 500 feet (ft) and approximately 1,200 ft offshore. This mission was flown to collect post-Nor'Ida data for assessing incremental changes since the last surveys, flown in 2008 and 2009, and the data can be used in the assessment of future coastal change. The images provided in this report are Joint Photographic Experts Group (JPEG) images. Exiftool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of any feature in the images. These photographs document the configuration of the barrier islands and other coastal features at the time of the survey. Table 1 provides detailed information about the GPS location, name, date, and time each of the 2,381 photographs was taken along with links to each photograph. The photography is organized into segments, also referred to as contact sheets. Each segment represents approximately 5 minutes of flight time. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files.

Maryland, North Carolina, Virginia↗
USGS2015

Post-Hurricane Ivan coastal oblique aerial photographs collected from Crawfordville, Florida, to Petit Bois Island, Mississippi, September 17, 2004

The U.S. Geological Survey (USGS) conducts baseline and storm response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms. On September 17, 2004, the USGS conducted an oblique aerial photographic survey from Crawfordville, Florida, to Petit Bois Island, Mississippi aboard a Piper Navajo Chieftain (aircraft) at an altitude of 500 feet (ft) and approximately 1,000 ft offshore. This mission was flown to collect post-Hurricane Ivan data for assessing incremental changes in the beach and nearshore area since the last survey in 2001, and the data can be used in the assessment of future coastal change. The images provided in this report are Joint Photographic Experts Group (JPEG) images. ExifTool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of any feature in the images. These photographs document the state of the barrier islands and other coastal features at the time of the survey. Pages containing thumbnail images of the photographs, referred to as contact sheets, were created in 5-minute segments of flight time. These segments can be found on the Photos and Maps page. The photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. Table 1 provides detailed information about the GPS location, image name, date, and time for each of the 3,381 photographs taken, along with links to each photograph. The photographs are organized into segments, also referred to as contact sheets, and represent approximately 5 minutes of flight time. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided, which can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files.

Alabama, Florida, Mississippi↗
USGS2014

Post-Hurricane Sandy coastal oblique aerial photographs collected from Cape Lookout, North Carolina, to Montauk, New York, November 4-6, 2012

The U.S. Geological Survey (USGS) conducts baseline and storm response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms. On November 4-6, 2012, approximately one week after the landfall of Hurricane Sandy, the USGS conducted an oblique aerial photographic survey from Cape Lookout, N.C., to Montauk, N.Y., aboard a Piper Navajo Chieftain (aircraft) at an altitude of 500 feet (ft) and approximately 1,000 ft offshore. This mission was flown to collect post-Hurricane Sandy data for assessing incremental changes in the beach and nearshore area since the last survey in 2009. The data can be used in the assessment of future coastal change. The photographs provided here are Joint Photographic Experts Group (JPEG) images. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of the feature in the images. These photos document the configuration of the barrier islands and other coastal features at the time of the survey. Exiftool was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. Table 1 provides detailed information about the GPS location, image name, date, and time each of the 9,481 photographs were taken, along with links to each photograph. The photographs are organized in segments, also referred to as contact sheets, and represent approximately 5 minutes of flight time. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files.

Delaware, Maryland, New Jersey, New York, North Ca↗
USGS2013

Archive of post-Hurricane Isabel coastal oblique aerial photographs collected during U.S. Geological Survey Field Activity 03CCH01 from Ocean City, Maryland, to Fort Caswell, North Carolina and Inland from Waynesboro to Redwood, Virginia, September 21 - 23, 2003

On September 21 - 23, 2003, the United States Geological Survey (USGS) conducted an oblique aerial photographic survey along the Atlantic coast from Ocean City, Md., to Fort Caswell, N.C., and inland oblique aerial photographic survey from Waynesboro to Redwood, Va., aboard a Navajo Piper twin-engine airplane. The coastal survey was conducted at an altitude of 500 feet (ft) and approximately 1,000 ft offshore. For the inland photos, the aircraft tried to stay approximately 500 ft above the terrain. These coastal photos were used to document coastal changes like beach erosion and overwash caused by Hurricane Isabel, while the inland photos looked for potential landslides caused by heavy rains. The photos may also be used as baseline data for future coastal change analysis. The USGS and the National Aeronautics and Space Administration (NASA) surveyed the impact zone of Hurricane Isabel to better understand the changes in vulnerability of the Nation’s coasts to extreme storms (Morgan, 2009). This report serves as an archive of photographs collected during the September 21 - 23, 2003, post-Hurricane Isabel coastal and inland oblique aerial survey along with associated survey maps, KML files, navigation files, digital Field Activity Collection System (FACS) logs, and Federal Geographic Data Committee (FGDC) metadata. Refer to the Acronyms page for expansions of all acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 03CCH01 tells us the data were collected in 2003 for the Coastal Change Hazards (CCH) study and the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the ID number. The photographs provided here are Joint Photographic Experts Group (JPEG) scanned images of the analog 35 millimeter (mm) color positive slides. The photograph locations are estimates of the location of the plane (see the Navigation page). The metadata values for photo creation time, GPS latitude, GPS longitude, GPS position (latitude and longitude), keywords, credit, artist, caption, copyright, and contact were added to each photograph's EXIF header using EXIFtool (Subino and others, 2012). Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet, or, when viewing the Google Earth KML file, by clicking on the marker and then clicking on either the thumbnail or the link below the thumbnail. Nathaniel Plant (USGS - St. Petersburg, Fla.), and Ann Marie Ascough (formerly contracted at the USGS - St. Petersburg, Fla.) helped with the creation of KML files. To view the photos and survey maps, proceed to the Photos and Maps page.

Maryland, North Carolina, Virginia↗
USGS2013

Baseline coastal oblique aerial photographs collected from Pensacola, Florida, to Breton Islands, Louisiana, February 7, 2012

The U.S. Geological Survey (USGS) conducts baseline and storm response photography missions to document and understand the changes in vulnerability of the Nation's coasts to extreme storms (Morgan, 2009). On February 7, 2012, the USGS conducted an oblique aerial photographic survey from Pensacola, Fla., to Breton Islands, La., aboard a Piper Navajo Chieftain at an altitude of 500 feet (ft) and approximately 1,000 ft offshore. This mission was flown to collect baseline data for assessing incremental changes since the last survey, and the data can be used in the assessment of future coastal change. The photographs provided here are Joint Photographic Experts Group (JPEG) images. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of the feature in the images (see the Navigation Data page). These photos document the configuration of the barrier islands and other coastal features at the time of the survey. The header of each photo is populated with time of collection, Global Positioning System (GPS) latitude, GPS longitude, GPS position (latitude and longitude), keywords, credit, artist (photographer), caption, copyright, and contact information using EXIFtools (Subino and others, 2012). Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. Table 1 provides detailed information about the assigned location, name, data, and time the photograph was taken along with links to the photograph. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files (see the Photos and Maps page).

Alabama, Florida, Louisiana, Mississippi↗
USGS2012

Archive of post-Hurricane Charley coastal oblique aerial photographs collected during U.S. Geological Survey field activity 04CCH01 from Marco Island to Fort DeSoto, Florida, August 15, 2004

On August 15, 2004, the U.S. Geological Survey (USGS) conducted an oblique aerial photographic survey off the southwest coast of Florida, from Marco Island to Fort DeSoto, aboard a Navajo Chieftain airplane, tail number N2KK, at an altitude of 500 ft and approximately 1000 ft offshore. These photographs were used to document coastal changes such as beach erosion and overwash caused by Hurricane Charley. They will also be used as baseline data for future coastal change. The oblique photography also served as qualitative ground truthing for the Experimental Advanced Airborne Research Lidar (EAARL) coastal topography and bathymetry data collected on August 16, 2004 (Bonisteel and others, 2009). This report serves as an archive of photographs collected during the August 15, 2004, post-Hurricane Charley coastal oblique aerial survey along with associated flight path maps, KML files, navigation files, digital Field Activity Collection System (FACS) logs, and Federal Geographic Data Committee (FGDC) metadata. Refer to the Acronyms page for expansions of all acronyms and abbreviations used in this report. The USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) assigns a unique identifier to each cruise or field activity. For example, 04CCH01 tells us the data were collected in 2004 for the Coastal Change Hazards (CCH) study and the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the ID number. Two separate records of flight navigation were collected during the survey. The first was a continuous ASCII text file from the PLGR that recorded only latitudes, longitudes, and altitudes every 30 sec for the entire flight. No time values were recorded by the PLGR. The second navigation record was recorded by a Trimble Centurion GPS and converted to subtitles on the video, using a Compix Titler unit. The video was shot continuously during the survey. The video subtitles recorded day, month, year, latitude, longitude, and time in hours, minutes, and seconds. In order to produce a digital record of the navigation values that included latitude, longitude, and time, each was manually extracted from the video every 5 min, and these values were matched to the latitude and longitude in the PLGR file. Next, the time was interpolated between these 5-min fixes using Excel to produce time values for each navigation fix recorded in the PLGR file. The location of each photograph taken was determined in the following manner. A Nikon MF-14 data back marks the time each photograph was acquired on the lower right corner of the image in day, hour, and minute format (in UTC). These values were entered from the photographs into an Excel spreadsheet. It is assumed for the purposes of locating the images that the photographs were taken at a constant rate during any given minute of flight. To assign the time value in seconds to each photograph, the number of photographs taken during each minute was evenly distributed across that minute. For example, if 15 photographs were taken during minute 19:00:00, we assume that a picture was taken every 4 sec. The photographs were assigned the time values 19:00:00, 19:00:04, 19:00:08, and so on. The video time navigation file was then merged with the new interpolated photograph file based on time to produce the point of which each photograph was collected. As a result, the positions assigned to each photograph are an estimate of the aircraft position, not the location of the landmark photographed. The photographs provided here are JPEG scanned images of the analog slides. The metadata values for photo creation time, GPS latitude, GPS longitude, GPS position, keywords, credit, artist, caption, copyright, and contact were added to each photograph's EXIF header using EXIFtools (see the Software page). Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet, or, when viewing the Google Earth KML file, by clicking on the marker and then clicking on either the thumbnail or the link below the thumbnail. The KML files were created using the photographic navigation files and the CreateKML JavaScript (see the Software page). To view the survey maps and navigation files, and for more information about these items, see the Navigation page. Figure 1 displays the acquisition geometry. The tables provide detailed information about the assigned location, name, data, and time the photograph was taken along with links to the photo and corresponding 5-min contact sheet. Refer to table 1 and table 2 for details of the northern and southern county photographs, respectively.

Florida↗
USGS2007

Research on the impacts of past and future hurricanes on the endangered Florida manatee

U.S. Geological Survey (USGS) research on Florida manatees (Trichechus manatus latirostris) from 1982 through 1998 identified lower apparent survival rates for adult manatees during years when Hurricane Elena (1985), the March "Storm of the Century"(1993), and Hurricane Opal (1995) hit the northern coast of the Gulf of Mexico. Although our analysis showed that a significant number of our monitored individual manatees failed to return to their winter homes after these storms, their actual fate remains unknown. With the aid of new satellite technology to track manatees during storms and new statistical techniques to determine survival and emigration rates, researchers are working to understand how hurricanes impact the endangered species by studying manatees caught in the path of the destructive hurricanes of 2004 and 2005.

Florida↗
USGS2002

Subsurface controls on historical subsidence rates and associated wetland loss in southcentral Louisiana

Two regional releveling profiles and six tide gauges provide a basis for evaluating recent rates of delta plain subsidence in southcentral Louisiana . Analyses of these records demonstrate close correlations among highest historical rates of subsidence , rapid wetland losses, large volume hydrocarbon production, and probable reactivation of deep subsurface faults. Other researchers have demonstrated that the highest geological subsidence rates of the Mississippi delta plain (<3 mm/yr) correspond closely to the thickest Holocene sediments that fill the underlying incised valley. Within that geologic framework, highest historical subsidence rates (as much as 23 mm/yr) correspond to surface projections of the reactivated Lake Hatch and Golden Meadow fault zones and to individual oil and gas fields. The initial acceleration and subsequent decline in rates of wetland loss in southcentral Louisiana are attributed partly to increased and then possibly decreased rates of subsidence that were related to increased and then decreased rates of fluid production. Decreases in subsurface pore pressures associated with gas production were so large that the state of stress was altered and critically stressed faults were likely reactivated. Subsidence rates in coastal Louisiana associated with natural compaction and dewatering of Holocene deltaic sediments should decrease with time. Therefore historical rates of delta plain subsidence that accelerate and typically exceed geological subsidence rates are most likely influenced by anthropogenic activities, such as subsurface fluid extraction.

Louisiana↗
USGS1979

Enhancement of Landsat images for lineament analysis in the area of the Salina Basin, New York and Pennsylvania

Digital image processing of Landsat images of New York and Pennsylvania was undertaken to provide optimum images for lineament analysis in the area of the Salina Basin. Preliminary examination of Landsat images from photographic prints indicated sufficient differences between the spectral bands of the Landsat Multispectral Scanner (MSS) to warrant digital processing of both MSS band 7 and MSS band 5. Selective contrast stretching based on analysis of the Landsat MSS histograms proved to be the most important factor affecting the appearance of the images. A three-point linear stretch using the two end points and a middle point to the Landsat frequency distribution was most successful. The flexibility of the REMAPP image processing system was helpful in creating such custom-tailored stretches. An edge enhancement was tested on the MSS band 5 image, but was not used. Stereoscopic Landsat images acquired from adjacent orbits aided recognition of topographic features; the area of stereoscopic coverage could be increased by utilizing the precession of Landsat-1?s orbit . Improvements in the digitally processed scenes did affect the analysis of lineaments for the New York area; on the enhanced MSS band 5 image, an ENE trending set of lineaments is visible, which was not recognized from other images.

Open-File Report↗
USGS1978

Discrimination of hydrothermally altered rocks along the Battle Mountain-Eureka, Nevada, mineral belt using Landsat images

Landsat Multispectral Scanner (MSS) images of the northwestern part of the Battle Mountain-Eureki, Nevada mineral belt were evaluated for distinguishing hydrothermally altered rocks associated with porphyry copper and disseminated gold deposits. Detection of altered rocks from Landsat is based on the distinctive spectral reflectance of limonite present at coatings on weathered surfaces Some altered rocks are visible as bleached areas in individual MSS bands; however, they cannot be consistently distinguished from unaltered rocks with high albedo nor from bright areas resulting .from topographic slope. Black-and-white ratio images were generated to subdue .topographic effects, and three ratio images were composited in color to portray spectral radiance differences, forming an image known as a color-ratio composite (CRC). The optimum CRC image for this area has MSS 4/5 as blue, MSS 4/6 as yellow, and MSS 6/7 as magenta, and differs in two respects from most CRC images of arid areas. First, as a result of the increased vegetation cover in the study area, MSS 5/6 was replaced by MSS 4/6 as the yellow layer. Second, 70 mm positive transparencies were replaced by large format images (64 cm), thereby improving the internal registration of the CRC image and the effective spatial resolution. The pattern of limonitic rocks depicted in the CRC closely agrees with the mapped pattern of the alteration zones at the Copper Canyon and Copper Basin porphyry copper deposits. Certain west-facing topographic slopes in the altered areas are depicted as unaltered in the CRC, apparently due to atmospheric scattering, and illustrate the need for atmospheric correction. The disseminated gold deposits at Gold Acres and Tenabo are poorly represented in the CRC because of the general absence of limonite on these deposits. The presence of unaltered limonitic sedimentary and volcanic rocks is the largest obstacle to discriminating altered areas within the mineral belt. Reflectance spectra, made in situ and in the laboratory indicate differences between altered and unaltered rocks in the Spectra region between 1.1 ?m and 2.5 ?m. Such differences may be detectable by a remote scanner with a longer wavelength range than current Landsat MSS (0.6 ?m-1.1 ?m).

Open-File Report↗