TY - Generic T1 - Field mapping and fracture characterization techniques predict groundwater preferential flow paths in fractured bedrock aquifers, Nashoba Terrane, MA T2 - AGU Fall Conference, 2005 Y1 - 2005 A1 - Alex K Manda A1 - Stephen B Mabee A1 - Hubbs, S. A. KW - #StaffPubs KW - aquifers KW - BEDROCK KW - characterization KW - fractured materials KW - fractures KW - ground water KW - Hydrogeology 21 KW - mapping KW - massachusetts KW - Middlesex County Massachusetts KW - movement KW - Nashoba terrane KW - patterns KW - preferential flow KW - recharge KW - reservoir properties KW - substrates KW - United States AB - A study examining the relationship between fracture characteristics and groundwater was undertaken in the crystalline Nashoba Terrane of eastern Massachusetts. The Nashoba Terrane, a fault-bounded, highly deformed sliver of Paleozoic igneous and metamorphic rocks, covers an area of 600 sq km about 50 km northwest of Boston. Increasing industrial development coupled with population growth place significant pressure on developers to provide sufficient potable water for the population. To aid water development and management, this study examined fracture characteristics at regional, quadrangle and wellfield scales. The regional-scale work involved recording over 4000 structural measurements from 80 outcrops in the terrane. Fracture information recorded at each data station included strike and dip, trace length, spacing, termination, and fracture type. Preliminary results show that hydrostructural domains can be defined from combinations of fracture characterization and rock types. These domains are used to conceptualize general groundwater flow patterns in the subsurface: steeply dipping fractures, such as partings parallel to foliation enhance recharge potential and impose strong flow anisotropy. A different character is observed if steeply dipping joints intersect sheeting joints. In this instance, both recharge and lateral flow will be enhanced and flow anisotropy will be reduced. The distribution and intensity of particular fracture sets varies as a function of rock type, proximity to major features and local stress states. Partings parallel to foliation are prevalent in gneissic rocks whereas sheeting joints are more common in igneous rocks. Common joints are the most prevalent fractures, present in all rock types across the entire terrane. Quadrangle and wellfield scale data can be used to validate the regional-scale conceptual models. A comprehensive well-yield database was created to test the proposed models. Over 500 water wells in the terrane were evaluated to determine regions with high and low yield. The findings were evaluated in terms of location with respect to newly defined hydrostructural domain maps at both regional and quadrangle scales. Application of these hydrostructural domains in field studies can be useful not only in characterizing fracture intensity and distribution, but can shed more light on the potential of intersecting subsurface zones that could be exploited for economic gain. JF - AGU Fall Conference, 2005 PB - American Geophysical Union : Washington, DC, United States CY - United States VL - 86 SN - 00963941 IS - 52, Suppl.52, Suppl. N1 - Accession Number: 2009-053313; Conference Name: American Geophysical Union 2005 fall meeting; San Francisco, CA, United States; Conference Date: 20051205; Language: English; Coordinates: N420800N424400W0710200W0715300; Coden: EOSTAJ; Collation: -1; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200930; Monograph Title: AGU 2005 fall meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Eos, Transactions, American Geophysical Union ER - TY - Generic T1 - Fracture characterization of crystalline bedrock for groundwater investigations; an example from the Marlborough Quadrangle, Massachusetts T2 - Abstracts with Programs - Geological Society of America Y1 - 2004 A1 - Scott A Salamoff A1 - Stephen B Mabee A1 - Joseph P Kopera A1 - Donald U Wise KW - #StaffPubs KW - aquifers KW - Assabet River Fault KW - BEDROCK KW - characterization KW - controls KW - crystalline rocks KW - fractured materials KW - fractures KW - geographic information systems KW - ground water KW - Hydrogeology 21 KW - hydrology KW - information systems KW - joints KW - Marlborough Quadrangle KW - massachusetts KW - Middlesex County Massachusetts KW - permeability KW - preferential flow KW - recharge KW - style KW - testing KW - theoretical models KW - United States AB - Integration of a wide array of structural data with well-field hydrologic testing is increasingly recognized as a critical step in understanding groundwater flow behavior and recharge in crystalline bedrock aquifers (Lyford et al., 2003, Walsh and Lyford, 2002). The Marlborough Quadrangle, about 40 km west of Boston, was selected as a test case of how a state geological survey can most effectively and efficiently collect and present such data in order to better constrain conceptual models of groundwater flow in general and to be of maximum use for hydrologists and consultants working on specific local problems. In this study, 3200 structural measurements were taken by a two-person team over a nine-week period at 68 stations distributed throughout the quadrangle and keyed into a GIS database. Specialized data sheets allowed efficient recording and digitization of orientations, lengths, spacing and mineralization, and separation of various classes of joints and veins. Fault data also included motion direction and sense. Summary maps in GIS format include standard geologic map bases overlain by typical rose diagrams and stereograms and maps such as fracture domains and trajectories, sheeting distribution, foliation trajectories, bedrock elevations, generalized piezometric surface configuration, and overburden type and thickness with separations into permeability class. Geology of the quadrangle can be separated into three zones: (a) north of the Assabet River Fault (ARF), (b) the area between the ARF and 1.5 km-wide Bloody Bluff Fault Zone (BBFZ), and (c) south of the BBFZ. Generalized foliations in the zones are: (a) 215, 50N, (b) 240, 65N, and (c) 270, 45N. Two pervasive, steeply-dipping (>60 degrees ) fracture sets occur throughout the quadrangle: an older 150 degrees set that includes sulfide-bearing veins and fracture surfaces along the ARF and a 015 degrees set of largely unmineralized common joints, macrojoints (>3 m length) and joint zones (av. 1.2 m width). Sheeting and unloading joints are generally coincident with shallow dipping foliation in (c) but cross-cut foliation in (a) and (b). We believe this approach will provide hydrologists and consultants with basic framework data that will expedite and improve the planning of subsurface investigations, construction activities and groundwater exploration. JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 36 SN - 00167592 UR - https://gsa.confex.com/gsa/2004NE/finalprogram/abstract_70321.htm IS - 22 N1 - Accession Number: 2005-077195; Conference Name: Geological Society of America, Northeastern Section, 38th annual meeting; Geological Society of America, Southeastern Section, 53rd annual meeting; Washington, DC, United States; Conference Date: 20040325; Language: English; Coordinates: N421800N421800W0713000W0713000; Coden: GAAPBC; Collation: 1; Collation: 113; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200524; Monograph Title: Geological Society of America, Northeastern Section, 38th annual meeting; Geological Society of America, Southeastern Section, 53rd annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - Generic T1 - Fracture patterns across two terrane boundaries in eastern Massachusetts; implications for regional groundwater flow and recharge T2 - Abstracts with Programs - Geological Society of America Y1 - 2006 A1 - Stephen B Mabee A1 - Joseph P Kopera KW - #StaffPubs KW - Avalon Zone KW - BEDROCK KW - eastern Massachusetts KW - faults KW - foliation KW - fractures KW - ground water KW - Hydrogeology 21 KW - joints KW - massachusetts KW - Merrimack Belt KW - movement KW - observations KW - patterns KW - properties KW - recharge KW - shear zones KW - style KW - terranes KW - United States AB - The integration of structural data and field-based observations is becoming increasingly critical in understanding groundwater flow behavior and recharge potential. Over the past 3 years, the Office of the Massachusetts State Geologist (OMSG) has collected 8225 fracture measurements from 187 stations across 3 adjacent quadrangles as part of its bedrock geologic mapping program. These data provide a north-south transect across the Nashoba Terrane and its boundaries with the Merrimack Belt and Avalon Terranes in eastern Massachusetts. Areas with similar fracture patterns can be grouped into "hydrostructural domains" with distinct hydrogeologic properties. Within the above transect, hydrostructural domains were observed to closely correspond with bedrock lithology and ductile structure, and therefore, tectonic history. Such domains are commonly bounded by faults or intrusive contacts. Common features observed across all domains include a NE-striking regional foliation with corresponding NW-striking, steeply-dipping cross-joints. Strongly layered metasedimentary and metavolcanic rocks of the Merrimack Belt and the Marlborough Formation in the Nashoba Terrane tend to have the most pervasive and closely-spaced foliation-parallel fractures (FPF). Foliation intensity and FPF generally increases towards shear zones and regional fault systems, especially within granites and gneisses. The moderate to steeply dipping, well-developed FPF in these rocks provides a potentially excellent conduit for vertical recharge and a strong NE-trending regional anistropy that may control groundwater flow. Granitoidal rocks have very consistent NS-EW orthogonal networks of vertical fractures and subhorizontal sheeting joints, providing excellent potential for vertical recharge and near-surface lateral flow. Features such as small brittle faults, fracture zones, fold axes, and fracture sets distinct to each domain may dominate local groundwater flow and recharge. Abstract 116563 modified by 72.70.224.253 on 7-12-2006 JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 38 SN - 00167592 UR - https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_116563.htm IS - 77 N1 - Accession Number: 2010-054322; Conference Name: Geological Society of America, 2006 annual meeting; Philadelphia, PA, United States; Conference Date: 20061022; Language: English; Coden: GAAPBC; Collation: 1; Collation: 434; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 201030; Monograph Title: Geological Society of America, 2006 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - Generic T1 - A new way of looking at, and mapping, bedrock; the hydrostructural domain map of the Ayer Quadrangle, northeastern Massachusetts T2 - Abstracts with Programs - Geological Society of America Y1 - 2006 A1 - Joseph P Kopera A1 - Stephen B Mabee KW - #StaffPubs KW - aquifers KW - Ayer Quadrangle KW - BEDROCK KW - faults KW - foliation KW - fracture zones KW - fractures KW - ground water KW - Hydrogeology 21 KW - joints KW - mapping KW - massachusetts KW - measurement KW - Merrimack Belt KW - movement KW - Nashoba terrane KW - northeastern Massachusetts KW - observations KW - orientation KW - physical properties KW - recharge KW - shear zones KW - Structural geology 16 KW - style KW - United States AB - While traditional bedrock geologic maps contain valuable information, they commonly lack data on fractures and physical properties of the rock. The increased need for better understanding of groundwater behavior in bedrock aquifers has made this data critical. Hydrostructural domain maps reclassify bedrock based on fracture systems and physical properties that may have implications for groundwater flow and recharge. These maps are constructed from detailed field observations and measurements of 2000-3000 fractures from 60-70 stations across a 7.5' quadrangle. Hydrostructural domains are displayed on the map as traditional lithologic units would be, with detailed descriptions and photos of the fracture characteristics and physical properties of each hydrostructural "unit". In the Ayer Quadrangle, such domains closely correspond with bedrock lithology and ductile structural history. Steeply dipping metasedimentary rocks of the Merrimack Belt have pervasive, closely spaced, throughgoing fractures developed parallel to foliation, and therefore provide an excellent potential for vertical recharge. Where these rocks are intensely cut by a strong subhorizontal cleavage, a parallel fracture set dominates providing an opportunity for lateral flow. Massive granites generally have a well developed, widely-spaced orthogonal network of fracture zones which may provide excellent local recharge. High-grade gneisses of the Nashoba Terrane have poorly developed fracture sets except near regional shear zones, where foliation parallel fractures and cross-joints may provide good vertical recharge and provide a strong northeast trending flow anisotropy. These maps are intended to provide a regional-scale information to assist in site-specific groundwater investigations. We believe that such maps are an example of how new types of geologic maps can, and must, be developed to address changing societal needs. JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 38 SN - 00167592 UR - https://gsa.confex.com/gsa/2006AM/finalprogram/abstract_116561.htm IS - 77 N1 - Accession Number: 2008-100620; Conference Name: Geological Society of America, 2006 annual meeting; Philadelphia, PA, United States; Conference Date: 20061022; Language: English; Coden: GAAPBC; Collation: 1; Collation: 166; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200816; Monograph Title: Geological Society of America, 2006 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER -