¹Isabelle S. Mattia,¹Matthew J. Genge,²Martin D. Suttle
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70105]
¹Department of Earth Sciences, Imperial College London, London, UK
²School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Fossil micrometeorites (MMs) recovered from lithified sedimentary rocks, particularlyiron-rich (I-type) cosmic spherules (CSs) provide valuable insights into past dust-forming events.Their abundances, when combined with estimates of local sedimentation rates can be used toreconstruct the flux of extraterrestrial dust. However, their preservation in the geological recordis highly susceptible to postdepositional diagenetic processes, complicating their quantificationand past flux calculations. This study investigated lenticular calcitic concretions as potential sitesof enhanced preservation of fossil MMs. A total of 17–18 I-types (but no silicate dominatedspherules, S-types) were recovered from Cenomanian sediments within the Cretaceous ChalkSupergroup at Lulworth Cove, England. The I-types, identified by optical and SEM–EDXanalyses, exhibited typical dendritic textures and varying degrees of alteration, including mottledsurfaces and loss of Ni and Cr by leaching. Calcitic concretions yielded a comparableconcentration of I-types to the surrounding hosting marl, but due to the added carbonatecementation during their growth, preservation per original sediment volume was shown to beenhanced (potentially by up to ~60%). Calcitic concretions can therefore act asmicroenvironments that enhance fossil MM preservation by limiting complete dissolution andloss of I-types. To constrain possible diagenetic effects on fossil MM quantification, futurestudies should compare cosmic dust yields across multiple sites exposing the same targetedsedimentary horizon.