Inherit defaut wpf style

gistfile1.xml

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <StackPanel>  
    <StackPanel.Resources>
      <Style TargetType="TextBlock">
        <Setter Property="Background" Value="Red" />
      </Style>
      <Style TargetType="TextBlock" x:Key="Custom1">
        <Setter Property="Foreground" Value="Blue" />
      </Style>
      <Style TargetType="TextBlock" x:Key="Custom2" BasedOn="{StaticResource {x:Type TextBlock}}">
        <Setter Property="Foreground" Value="Blue" />
      </Style>
    </StackPanel.Resources>
    <TextBlock>Defaut</TextBlock>
    <TextBlock Style="{StaticResource Custom1}">Custom 1 : background remis par defaut</TextBlock>
    <TextBlock Style="{StaticResource Custom2}">Custom 2 : background repris de Default</TextBlock>
  </StackPanel>
</Page>