missing right paranthesis Oracle while creating table : oracle error

SQL> desc user_details;
 Name                                      Null?    Type
 ----------------------------------------- -------- --------------

 USER_ID                                            NUMBER(38)
 NAME                                               VARCHAR2(20)
 DOB                                                DATE
 CONTACT                                            NUMBER(38)
 EMAIL                                     NOT NULL VARCHAR2(50)
 TYPE                                               VARCHAR2(4)


create table user_reg
(
reg_id int primary key,
pass varchar(50),
email varchar(20) foreign key preferences user_details(user_id)
);

this is what error i got while creating table user_reg 