-<xsd:schema elementFormDefault="qualified" attributeFormDefault="unqualified" targetNamespace="http://www.witsml.org/schemas/131" version="1.3.1">
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<!--
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 <xsd:include schemaLocation="typ_dataTypes.xsd"/>
<!--
 -->
-<xsd:group name="grp_formationMarker">
-<xsd:annotation>
 <xsd:documentation>The non-contextual content of a WITSML Formation Marker.</xsd:documentation>
 </xsd:annotation>
-<xsd:sequence>
-<xsd:element name="mdPrognosed" type="witsml:measuredDepthCoord" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Prognosed measured depth. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="tvdPrognosed" type="witsml:wellVerticalDepthCoord" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Prognosed true vertical depth. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="mdTopSample" type="witsml:measuredDepthCoord" minOccurs="1" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Sampled measured depth at top of marker. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="tvdTopSample" type="witsml:wellVerticalDepthCoord" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Sampled true vertical depth at top of marker. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="thicknessBed" type="witsml:lengthMeasure" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Bed Thickness. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="thicknessApparent" type="witsml:lengthMeasure" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Formation exposed along the wellbore. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="thicknessPerpen" type="witsml:lengthMeasure" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Perpendicular thickness. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="mdLogSample" type="witsml:measuredDepthCoord" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Logged measured depth at top of marker. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="tvdLogSample" type="witsml:wellVerticalDepthCoord" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Logged true vertical depth at top of marker. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="dip" type="witsml:planeAngleMeasure" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Angle of dip with respect to horizontal. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="dipDirection" type="witsml:planeAngleMeasure" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Interpreted downdip direction. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="chronostratigraphic" type="witsml:str32" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Chronostratigraphic classification. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="nameFormation" type="witsml:str32" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Formation name. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
-<xsd:element name="description" type="witsml:commentString" minOccurs="0" maxOccurs="1">
-<xsd:annotation>
 <xsd:documentation>Description of item and details. </xsd:documentation>
 </xsd:annotation>
 </xsd:element>
 </xsd:sequence>
 </xsd:group>
 </xsd:schema>