jboss-6.0.0.Final doesn't seem to have jboss-log4j.xml which was used to configure log4j settings in jboss5 (i.e. under server/default/conf/jboss-log4j.xml)
Apparently the name and location changed since release 6:
In the releases 4.x and 5.x it's located here:JBoss_HOME\server\default\conf\jboss-log4j.xml
Since the release 6.0.0 M1 it's located in the deploy folder: JBOSS_HOME\server\default\deploy\jboss-logging.xml
Source: http://www.mastertheboss.com/jboss-application-server/251-jboss-log4j-configuration.html