Diagenetic origin of nodules in the Sheepbed member, Yellowknife Bay formation, Gale crater, Mars

• Published in: Journal of Geophysical Research: Planets
• Main Authors: Stack, K. M., Grotzinger, J. P., Kah, L. C., Schmidt, M. E., Mangold, N., Edgett, K. S., Sumner, D. Y., Siebach, K. L., Nachon, M., Lee, R., Blaney, D. L., Deflores, L. P., Edgar, L. A., Fairén, A. G., Leshin, L. A., Maurice, S., Oehler, D. Z., Rice, M. S., Wiens, R. C.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Geophysical Union 2014
• Subjects: Mars Science Laboratory; Yellowknife Bay; diagenesis; concretions; Yellowknife
• Online Access: https://doi.org/10.1002/2014je004617

The Sheepbed member of the Yellowknife Bay formation in Gale crater contains millimeterâ€scale nodules that represent an array of morphologies unlike those previously observed in sedimentary deposits on Mars. Three types of nodules have been identified in the Sheepbed member in order of decreasing abundance: solid nodules, hollow nodules, and filled nodules, a variant of hollow nodules whose voids have been filled with sulfate minerals. This study uses Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI) images from the Mars Science Laboratory Curiosity rover to determine the size, shape, and spatial distribution of the Sheepbed nodules. The Alpha Particle Xâ€Ray Spectrometer (APXS) and ChemCam instruments provide geochemical data to help interpret nodule origins. Based on their physical characteristics, spatial distribution, and composition, the nodules are interpreted as concretions formed during early diagenesis. Several hypotheses are considered for hollow nodule formation including origins as primary or secondary voids. The occurrence of concretions interpreted in the Sheepbed mudstone and in several other sedimentary sequences on Mars suggests that active groundwater systems play an important role in the diagenesis of Martian sedimentary rocks. When concretions are formed during early diagenetic cementation, as interpreted for the Sheepbed nodules, they have the potential to create a taphonomic window favorable for the preservation of Martian organics. © 2014 American Geophysical Union. Issue Online: 13 August 2014; Version of Record online: 22 July 2014; Accepted manuscript online: 21 June 2014; Manuscript accepted: 18 June 2014; Manuscript revised: 15 May 2014; Manuscript received: 28 January 2014. We would like to thank the scientists and engineers of the MSL team, especially the MAHLI, Mastcam, ChemCam, and APXS payload uplink and downlink leads. We also thank M. Chan and D. Loope for constructive comments that helped to improve this manuscript. All data used in this paper can be obtained by ...