There are no defaults.  There are two actions to take here.  If the placemark as a `styleUrl` node, then you look up that style in the list of styles you parsed already.  For example, in the KML_Samples.kml, you'll find a Placemark with `<styleUrl>#downArrowIcon</styleUrl>`. you would chop off the # and then call `var style = styleCollection.getObject('downArrowIcon')` then merge is `dynamicObject.merge(style)`.  If `style` is undefined, just throw a `RuntimeError` for now.

If the placemark has an embedded style, instead of a styleUrl, then you just call `processStyle` passing in `dynamicObject`.