The ChemCam campaign at the fluvial sedimentary outcrop ‘‘Shaler’’ resulted in observations of 28 non-soil targets, 26 of which included active laser induced breakdown spectroscopy (LIBS), and all of which included Remote Micro-Imager (RMI) images. The Shaler outcrop can be divided into seven facies based on grain size, texture, color, resistance to erosion, and sedimentary structures. The ChemCam observations cover Facies 3 through 7. For all targets, the majority of the grains were below the limit of the RMI resolution, but many targets had a portion of resolvable grains coarser than 0.5 mm. The Shaler facies show significant scatter in LIBS spectra and compositions from point to point, but several key compositional trends are apparent, most notably in the average K2O content of the observed facies. Facies 3 is lower in K2O than the other facies and is similar in composition to the ‘‘snake,’’ a clastic dike that occurs lower in the Yellowknife Bay stratigraphic section. Facies 7 is enriched in K2O relative to the other facies and shows some compositional and textural similarities to float rocks near Yellowknife Bay. The remaining facies (4, 5, and 6) are similar in composition to the Sheepbed and Gillespie Lake members, although the Shaler facies have slightly elevated K2O and FeOT. Several analysis points within Shaler suggest the presence of feldspars, though these points have excess FeOT which suggests the presence of Fe oxide cement or inclusions. The majority of LIBS analyses have compositions which indicate that they http://dx.doi.org/10.1016/j.icarus.2014.07.025 0019-1035/Published by Elsevier Inc. ⇑ Corresponding author. E-mail addresses: rbanderson@usgs.gov (R. Anderson), jcb36@leicester.ac.uk (J.C. Bridges), amywill@ucdavis.edu (A. Williams), ledgar1@asu.edu (L. Edgar), aollila@unm. edu (A. Ollila), josh505@unm.edu (J. Williams), marion.nach@gmail.com (M. Nachon), nicolas.mangold@univ-nantes.fr (N. Mangold), Martin.Fisk@oregonstate.edu (M. Fisk), jschiebe@indiana.edu (J. Schieber), s.gupta@imperial.ac.uk (S. Gupta), gilles.dromart@ens-lyon.fr (G. Dromart), rwiens@lanl.gov (R. Wiens), stephane.lemouelic@univ-nantes. fr (S. Le Mouélic), olivier.forni@irap.omp.eu (O. Forni), nlanza@lanl.gov (N. Lanza), amezzacappa09@students.desu.edu (A. Mezzacappa), vsautter@mnhn.fr (V. Sautter), diana. l.blaney@jpl.nasa.gov (D. Blaney), bclark@spacescience.org (B. Clark), sclegg@lanl.gov (S. Clegg), olivier.gasnault@irap.omp.eu (O. Gasnault), jeremie.lasue@irap.omp.eu (J. Lasue), rich.leveille@gmail.com (R. Léveillé), Eric.LEWIN@obs.ujf-grenoble.fr (E. Lewin), sylvestre.maurice@irap.omp.eu (S. Maurice), newsom@unm.edu (H. Newsom), dvaniman@psi.edu (D. Vaniman). Icarus 249 (2015) 2–21 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/ locate/ icarus are mixtures of pyroxene and feldspar. The Shaler feldspathic compositions are more alkaline than typical feldspars from shergottites, suggesting an alkaline basaltic source region, particularly for the K2Oenriched Facies 7. Apart from possible iron-oxide cement, there is little evidence for chemical alteration at Shaler, although calcium-sulfate veins comparable to those observed lower in the stratigraphic section are present. The differing compositions, and inferred provenances at Shaler, suggest compositionally heterogeneous terrain in the Gale crater rim and surroundings, and intermittent periods of deposition