The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States

Horton, John D.; Juan, Carma A. San; Stoeser, Douglas B.

doi:10.3133/ds1052

Cited by 102 publications

(89 citation statements)

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“…In some cases, stream‐valley aquifers can extend across the boundaries of several PAs and (or) SHRs. The State Geologic Map Compilation (Horton et al ) does provide a basis for a relatively comprehensive identification of stream‐valley aquifers, but it is beyond the scope of this paper to undertake that effort. In some assessments of PAs, stream‐valley aquifers were not separated from the larger PA. For example, assessment of groundwater quality in the High Plains PA included wells located within stream‐valley aquifers (Gurdak et al ); in that study the stream‐valley aquifers were considered to be in hydrologic connection with the High Plains PA (Gutentag et al ).…”

Section: Discussionmentioning

confidence: 99%

“…SHRs typically consist of low permeability rocks or deposits, but can include locally productive aquifers. The basic building block for identifying SHRs were geologic units as identified on the Geologic Map of North America (Garrity and Soller ), with supplementary information obtained from the State Geologic Map Compilation (Horton et al ), to insure that SHRs consist of rocks of comparable age and lithology. SHRs also were assembled using additional analog and digital maps to insure that the geologic units within an SHR are of comparable geologic or physiographic setting (Fenneman and Johnson 1946; Frezon and Finn ; Reed and Bush ; Coleman and Cahan ).…”

Section: Discussionmentioning

confidence: 99%

“…Rocks of Archean and Proterozoic age were classified as crystalline. Lithologic categorization was based primarily on the relatively coarse‐resolution Geologic Map of North America (Garrity and Soller ), but also on the relatively fine‐resolution State Geologic Map Compilation (Horton et al ). The Geologic Map of North America was given priority because it provides consistency across state boundaries, whereas the state‐scale geologic maps do not.…”

Section: Methodsmentioning

confidence: 99%

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Secondary Hydrogeologic Regions of the Conterminous United States

Belitz¹,

Watson

Johnson

et al. 2018

Groundwater

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The U.S. Geological Survey (USGS) previously identified and mapped 62 Principal Aquifers (PAs) in the U.S., with 57 located in the conterminous states. Areas outside of PAs, which account for about 40% of the conterminous U.S., were collectively identified as "other rocks." This paper, for the first time, subdivides this large area into internally-consistent features, defined here as Secondary Hydrogeologic Regions (SHRs). SHRs are areas of other rock within which the rocks or deposits are of comparable age, lithology, geologic or physiographic setting, and relationship to the presence or absence of underling PAs or overlying glacial deposits. A total of 69 SHRs were identified. The number and size of SHRs identified in this paper are comparable to the number and size of PAs previously identified by the USGS. From a two-dimensional perspective, SHRs are complementary to PAs, mapped only where the PAs were not identified on the USGS PA map and not mapped where the PAs were identified. SHRs generally consist of low permeability rocks or deposits, but can include locally productive aquifers. The two maps, taken together, provide a comprehensive, national-scale hydrogeologic framework for assessing and understanding groundwater systems.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Secondary Hydrogeologic Regions of the Conterminous United States

Belitz¹,

Watson

Johnson

et al. 2018

Groundwater

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“… Samples listed numerically within regions, with stratigraphic age: EM – Early Mississippian (359–345 Ma); LD – Late Devonian (383–359 Ma); MD – Middle Devonian (393–383 Ma); ED – Early Devonian (419–393 Ma). Sample depositional group and formation determined from U.S. Geological Survey geologic map (Horton, ). All samples were crushed and apatites were separated using conventional heavy liquid and magnetic separation techniques.…”

Section: Methodsmentioning

confidence: 99%

“…The six representative samples discussed in text and Figure are bolded. Base map generated in ArcGIS using STRM 90m DEM relief shaping (Jarvis, Reuter, Nelson, & Guevara, ) overlain by U.S. Geological Survey geologic map (Horton, )…”

Section: Introductionmentioning

confidence: 99%

Post‐orogenic thermal history and exhumation of the northern Appalachian Basin: Low‐temperature thermochronologic constraints

Shorten

Fitzgerald

2019

Basin Research

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Apatite fission‐track (AFT) thermochronology and (U‐Th)/He (AHe) dating, combined with paleothermometers and independent geologic constraints, are used to model the thermal history of Devonian Catskill delta wedge strata. The timing and rates of cooling determines the likely post‐orogenic exhumation history of the northern Appalachian Foreland Basin (NAB) in New York and Pennsylvania. AFT ages generally young from west to east, decreasing from ~185 to 120 Ma. AHe single‐grain ages range from ~188 to 116 Ma. Models show that this part of the Appalachian foreland basin experienced a non‐uniform, multi‐stage cooling history. Cooling rates vary over time, ~1–2 °C/Myr in the Early Jurassic to Early Cretaceous, ~0.15–0.25 °C/Myr from the Early Cretaceous to Late Cenozoic, and ~1–2 °C/Myr beginning in the Miocene. Our results from the Mesozoic are broadly consistent with earlier studies, but with the integration of multiple thermochronometers and multi‐kinetic annealing algorithms in newer inverse thermal modeling programs, we constrain a Late Cenozoic increase in cooling which had been previously enigmatic in eastern U.S. low‐temperature thermochronology datasets. Multi‐stage cooling and exhumation of the NAB is driven by post‐orogenic basin inversion and catchment drainage reorganization, in response to changes in base level due to rifting, plus isostatic and dynamic topographic processes modified by flexure over the long (~200 Myr) post‐orogenic period. This study compliments other regional exhumation data‐sets, while constraining the timing of post‐orogenic cooling and exhumation in the NAB and contributing important insights on the post‐orogenic development and inversion of foreland basins along passive margins.

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