Understanding user behavior is at the heart of user interface design, but can only be quantified to some extent. Qualitatively analyzing individual usage sessions is especially important in open-ended tasks like literature search. In this paper, we present a visual representation of logging data that provides the basis for an in-depth analysis and annotation of search and exploration sessions. The visualization was developed to evaluate the citation-based literature discovery tool PUREsuggest and is thus aimed at visualizing logging data of a literature search system. Events are represented on a timeline in different layers as bars and icon-based glyphs, and contextualized by the additional visualization of item states and active user-set search modifiers such as filters or keywords throughout the session. We demonstrate the applicability of the visualization by evaluating excerpts of two user sessions as an example.