40Ar/39Ar ages of rocks collected from the Passage Canal area, Seward D-7 Quadrangle, Alaska

Frequently anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Benowitz, J.A., Layer, P.W., Wypych, Alicja, and Freeman, L.K., 2017, 40Ar/39Ar ages of rocks collected from the Passage Canal area, Seward D-7 Quadrangle, Alaska: Raw Data File RDF 2017-4, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

   Online Links:

   • <http://doi.org/10.14509/29721>

   Other_Citation_Details: 6 p.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -148.713905

   East_Bounding_Coordinate: -148.710235

   North_Bounding_Coordinate: 60.776767

   South_Bounding_Coordinate: 60.774973

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 2016

   Ending_Date: 2017

   Currentness_Reference: ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: report digital data

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a point data set.

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in decimal degrees.

      The horizontal datum used is World Geodetic System of 1984.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563000025.
      

7. How does the data set describe geographic features?

   rdf2017-4-summary-data-locations.csv

   Identification numbers, coordinates, sample descriptions, and summary ages of each sample (Source: Alaska Division of Geological & Geophysical Surveys)

   SAMPLE

   Label assigned in the field to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

   Generic example of a sample identifier: YYAAA9999X: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location or that multiple observations were recorded in the project database.

   LAB_SAMPLE_NUMBER

   Label used by the lab to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The lab sample number is typically identical to the field sample number. However, in some cases, the sample number provided by the lab does differ from the number assigned in the field. We provide both numbers to document instances in which the sample numbers in the lab files differ from the field sample number.

   COLLECTOR

   The geologist who collected the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

   The samples presented in this report were collected by the authors or other DGGS staff.

   LONGITUDE

   Longitude, WGS84 (Source: Alaska Division of Geological & Geophysical Surveys)

   Range of values
   Minimum:	-148.71207
   Maximum:	-148.71207
   Units:	decimal degrees

   LATITUDE

   Latitude, WGS84 (Source: Alaska Division of Geological & Geophysical Surveys)

   Range of values
   Minimum:	60.77587
   Maximum:	60.77587
   Units:	decimal degrees

   DATED_MATERIAL

   Indicates the type of material that was used for analysis (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The type of material that was selected for dating varied according to mineral composition and grainsize of the submitted rock sample. This field specifies whether the age was derived from a mineral separate (generally 1 to 10 individual crystals dated together as a single run), a single crystal, or the whole rock.

   MINERAL

   Indicates the mineral that was used for analysis (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The minerals selected for dating would typically be grains of biotite, hornblende, or muscovite.

   DESCRIP_1

   Description of the sample (Source: Alaska Division of Geological & Geophysical Surveys)

   Characters 1 to 254 of a brief sample or station description.

   DESCRIP_2

   Extension of the sample or station description for descriptions that are greater than 254 characters in length. (Source: Alaska Division of Geological & Geophysical Surveys)

   Characters greater than 254 of the sample or station description.

   INTEGRATED_AGE_MA

   Integrated age and age error in million years (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The values are a concatenation of the integrated age determination and the calculated error associated with the integrated age determination

   PLATEAU_AGE_MA

   Plateau age and age error in million years (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The values are a concatenation of the plateau age determination and the calculated error associated with the plateau age determination

   PLATEAU_REMARKS

   Comments and additional values that pertain to the plateau age determination method or interpretation. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Free text

   AGE_TYPE_PREFERRED

   Indicates the age type of the preferred age. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   A discussion of the preferred age for each analysis is provided in the accompanying lab report. The possible values are: plateau, isochron, weighted average, or integrated.

   PREFERRED_AGE

   The values are a concatenation of the preferred age determination and the calculated error associated with the preferred age determination (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The preferred age for each analysis is discussed in detail in the accompanying lab report.

   rdf2017-4-step-heating-data.csv

   Power output levels and resultant measurements from each sample run (Source: Alaska Division of Geological & Geophysical Surveys)

   SAMPLE

   Label assigned in the field to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys)

   Generic example of a sample identifier: YYAAA9999X: YY=last two digits of year, AAA=geologist's initials (one to three characters), 9999=unique station number, X= optional alpha character which indicates that multiple samples were collected at a given location or that multiple observations were recorded in the project database.

   LAB_SAMPLE_NUMBER

   Label used by the lab to identify the sample. (Source: Alaska Division of Geological & Geophysical Surveys and Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   The lab sample number is typically identical to the field sample number. However, in some cases, the sample number provided by the lab does differ from the number assigned in the field. We provide both numbers to document instances in which the sample numbers in the lab files differ from the field sample number.

   Laser_mW

   Laser output level in megawatts (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Value	Definition
   NULL	A NULL or blank values indicates that the values in the row were calculated by weighting the individual heating steps by the fraction of 39Ar released.

   Range of values
   Minimum:	500
   Maximum:	9000
   Units:	megawatts

   Integrated

   We indicate whether the values in the row were derived from a heating step or calculated by weighting the individual heating steps by the fraction of 39Ar released. (Source: Alaska Division of Geological & Geophysical Surveys)

   Value	Definition
   NULL	The values in the row were derived from a heating step
   Integrated	the values in this row were calculated by weighting the individual heating steps by the fraction of 39Ar released

   Cum39Ar

   Cumulative ratio of 39Argon released at this step (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Value	Definition
   NULL	A NULL or blank values indicates that the value was not applicable or not calculated by the lab

   Range of values
   Minimum:	0.0096
   Maximum:	1

   Me40Ar39Ar

   Measured 40Ar/39Ar ratio for each heating step, corrected for blank and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	5.31402
   Maximum:	8.90293

   Er40Ar39Ar

   The one sigma error for each 40Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00986
   Maximum:	0.07343

   Me37Ar39Ar

   The ratio of measured 37Ar to measured 39Ar for each heating interval for each sample corrected for blank and 37Ar and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00021
   Maximum:	0.00622

   Er37Ar39Ar

   The one sigma error for each 37Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00002
   Maximum:	0.007

   Me36Ar39Ar

   Ratio of measured 36Ar to measured 39Ar for each step interval for each sample corrected for blank and 39Ar decay (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00027
   Maximum:	0.01142

   Er36Ar39Ar

   The one sigma error for each 36Ar/39Ar measurement (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00001
   Maximum:	0.00306

   Atm40Ar

   Percent of 40Ar which is atmospheric in composition at each step level (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	1.22577
   Maximum:	38.0328

   ErAtm40Ar

   The one sigma error for the percent of 40Ar which is atmospheric in composition at each step level (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.04257
   Maximum:	10.18335

   MeCaK

   Ratio of Calcium to Potassium as determined from 37Ar/39Ar (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00038
   Maximum:	0.01141

   ErCaK

   The one sigma error for each Ca/K determination (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00004
   Maximum:	0.01284

   MeClK

   Ratio of Chlorine to Potassium as determined from 38Ar/39Ar (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00009
   Maximum:	0.00205

   ErClK

   The one sigma error for each Cl/K determination (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.00001
   Maximum:	0.00068

   Ar40Rad39ArK

   Ratio of radiogenic 40Ar to 39Ar derived from potassium (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	3.98127
   Maximum:	7.04025

   Er40ArRad39ArK

   One sigma error for each 40ArRad/39ArK value (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.01021
   Maximum:	0.90485

   AgeMa

   Calculated age for each temperature step for each sample (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	30.63
   Maximum:	53.82
   Units:	MA

   ErAgeMa

   One sigma error of the age determination of each heating step (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   Range of values
   Minimum:	0.13
   Maximum:	6.86
   Units:	MA

   WeightedAverageOfJFromStandards

   J value, calculated from the weighted average of standards placed in various positions in the nuclear reactor (Source: Geochronology Laboratory at the University of Alaska Fairbanks (UAF))

   WeightedAverageOfJFromStandards value and error

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Benowitz, J.A.
   • Layer, P.W.
   • Wypych, Alicja
   • Freeman, L.K.

2. Who also contributed to the data set?

   To comply with Alaska Railroad Corporation regulations and safely collect these samples, DGGS staff and field trip participants obtained written permission from the Alaska Railroad Corporation to cross the Right of Way. The sample collection and analyses were paid for with State of Alaska general funds. Sue Karl of the U.S. Geological Survey, Peter Oswald of the University of Alaska Anchorage, and Joe Kurtak provided outcrop-location information, discussion of geologic context, and assistance with the field trip.

3. To whom should users address questions about the data?
   Alaska Division of Geological & Geophysical Surveys
   Metadata Manager
   3354 College Road
   Fairbanks, AK 99709-3707
   USA
   

   (907)451-5039 (voice)
   (907)451-5050 (FAX)
   dggspubs@alaska.gov
   

   Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Why was the data set created?

This report presents 40Ar/39Ar step-heating geochronology results from a single outcrop of a mineralized near-trench intrusion exposed in a road cut near Whittier, Alaska. The outcrop is the best road-accessible occurrence of a Tertiary near-trench pluton in the region and is commonly visited by field trips, yet no prior geochronological data from this outcrop have been published. The 40Ar/39Ar step-heating geochronology results presented herein improve our understanding of the geology and structural history of intrusive rocks in the Turnagain Arm and Passage Canal area.

How was the data set created?

1. From what previous works were the data drawn?

2. How were the data generated, processed, and modified?

   Date: 2016 (process 1 of 2)

   Fieldwork - Fresh, unweathered samples from surficial outcrops were collected by DGGS field geologists; samples were selected based on presence of sufficiently large crystals and/or fresh glassy matrix.

   Date: 2016 (process 2 of 2)

   Sample preparation and analysis - Before processing, samples were examined under binocular microscope, or thin sections were prepared and scrutinized to eliminate the possibility of analyzing altered mineral phases. Rock samples that we found to be suitable for dating by 40Ar/39Ar geochronology analysis were submitted to the Geochronology Laboratory at the University of Alaska Fairbanks (UAF) where they were dated according to the protocols outlined in the accompanying report.

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   This data set is being released in the DGGS Raw Data File series. The information has been examined by several geologists familiar with the study area, but the data and accompanying report have not been formally reviewed for technical content or for conformity to the editorial standards of DGGS. Questions regarding the accuracy of the analytical values can be best answered by the originating lab.

2. How accurate are the geographic locations?

   Location data were collected using a Nexus 5x smartphone operating the Avenza Maps 2.0 Application (AvenzaMaps.com). Data were merged into an ArcGIS geodatabase. Location error for this process is undocumented. However, locations were visually checked and corrected using USGS and multiple imagery files in ArcGIS, and errors are estimated to be within 20 meters. Latitude and longitude are reported in the WGS84 datum.

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This data release is complete.

5. How consistent are the relationships among the observations, including topology?

   not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:

This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).

Use_Constraints:

Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

1. Who distributes the data set? (Distributor 1 of 1)
   Alaska Division of Geological & Geophysical Surveys
   Metadata Manager
   3354 College Road
   Fairbanks, AK 99709-3707
   USA
   

   (907)451-5039 (voice)
   (907)451-5050 (FAX)
   dggspubs@alaska.gov
   

   Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

2. What's the catalog number I need to order this data set?

   RDF 2017-4

3. What legal disclaimers am I supposed to read?

   The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

4. How can I download or order the data?
   • Availability in non-digital form:

     DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.

   • Cost to order the data: Contact DGGS for current pricing

   • Availability in digital form:

     Data format:	ASCII tabular files
     Network links:	<http://doi.org/10.14509/29721>

   • Cost to order the data: Free download

Who wrote the metadata?

Dates:

Last modified: 23-May-2017

Metadata author:

Alaska Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5039 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov

Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Metadata standard:

FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

• <http://www.dggs.alaska.gov/metadata/dggs.ext>