Spatial_Domain Description_of_Geographic_Extent Mandatory. Bounding_Coordinates Elevation_Minimum Optional. Bounding_Coordinates Elevation_Maximum Optional. Identification_Information Taxonomy Optional. Taxonomy Keywords/Taxon Mandatory, repeatable. Keywords/Taxon Taxonomic_Keyword_Thesaurus Mandatory. Keywords/Taxon Taxonomic_Keywords Mandatory, repeatable. Taxonomy Taxonomic_System Mandatory if applicable. Taxonomic_System Classification_System/Authority Mandatory, repeatable. Classification_System/Authority Classification_System_Citation Mandatory. Classification_System/Authority Classification_System_Modifications Mandatory if applicable. Taxonomic_System Identification_Reference Mandatory if applicable, repeatable. Taxonomic_System Identifier Optional, repeatable. Taxonomic_System Taxonomic_Procedures Mandatory. Taxonomic_System Taxonomic_Completeness Mandatory if applicable. Taxonomic_System Vouchers Mandatory if applicable, repeatable. Vouchers Specimen Mandatory. Vouchers Repository Mandatory. Taxonomy General_Taxonomic_Coverage Optional. Taxonomy Taxonomic_Classification Mandatory. Taxonomic_Classification Taxon_Rank_Name Mandatory. Taxonomic_Classification Taxon_Rank_Value Mandatory. Taxonomic_Classification Applicable_Common_Name Optional, repeatable. Taxonomic_Classification Taxonomic_Classification Mandatory if applicable, repeatable. Identification_Information Analytical_Tool Mandatory if applicable, repeatable. Analytical_Tool Analytical_Tool_Description Mandatory. Analytical_Tool Tool_Access_Information Mandatory. Analytical_Tool Tool_Contact Optional. Analytical_Tool Tool_Citation Optional. Tool_Access_Information Tool_Network_Resource_Name Mandatory if applicable, repeatable. Tool_Access_Information Tool_Access_Instructions Mandatory. Tool_Access_Information Tool_Computer_and_Operating_System Optional. Lineage Methodology Mandatory if applicable, repeatable. Methodology Methodology_Type Mandatory. Methodology Methodology_Identifier Optional, repeatable. Methodology_Identifier Methodology_Keyword_Thesaurus Mandatory. Methodology_Identifier Methodology_Keyword Mandatory, repeatable. Methodology Methodology_Description Mandatory. Methodology Methodology_Citation Mandatory if applicable, repeatable. Digital_Transfer_Information ASCII_File_Structure Mandatory if applicable. ASCII_File_Structure Record_Delimiter Mandatory if applicable. ASCII_File_Structure Number_Header_Lines Mandatory. ASCII_File_Structure Description_of_Header_Content Optional. ASCII_File_Structure Orientation Mandatory. ASCII_File_Structure Case_Sensitive Mandatory. ASCII_File_Structure Authentication Mandatory if applicable. ASCII_File_Structure Quote_Character Mandatory if applicable. ASCII_File_Structure Data_Field Mandatory, repeatable. Data_Field Data_Field_Name Mandatory. Data_Field Missing_Value_Code Mandatory if applicable. Data_Field Data_Field_Width_Delimiter Mandatory, choose this or Data_Field_Width. Data_Field Data_Field_Width Mandatory, choose this or Data_Field_Width_Delimiter. Range_of_Dates/Times Beginning_Geologic_Age Mandatory, choose this or Beginning_Date Range_of_Dates/Times Ending_Geologic_Age Mandatory, choose this or Ending_Date Single_Date/Time Geologic_Age Mandatory, choose this or Calendar_Date Beginning_Geologic_Age Geologic_Age Mandatory. Ending_Geologic_Age Geologic_Age Mandatory. Geologic_Age Geologic_Time_Scale Mandatory. Geologic_Age Geologic_Age_Estimate Mandatory. Geologic_Age Geologic_Age_Uncertainty Mandatory if applicable. Geologic_Age Geologic_Age_Explanation Mandatory if applicable. Geologic_Age Geologic_Citation Optional, repeatable.