Carbonate deposition in an ephemeral siliciclastic alluvial system: Jurassic Shuttle Meadow Formation, Newark Supergroup, Hartford Basin, USA

摘要: Abstract Nonmarine carbonate accumulation, from a sedimentologic perspective, has multiple possible origins: clastic load, springs, groundwater discharge, soil development, biochemical seasonal changes, cave speleothems, and eolian influx. Many of these carbonates contain diagnostic textures which origin is easy to ascertain. However, differentiating between spring/groundwater carbonates, especially in depositional systems dominated by siliciclastics, not always simple; here criteria for recognition are developed. Subsurface hydrology tectonic the basin, source rocks surrounding packaging extent question, as well their sedimentary structures fossil content, stable isotopic analyses can all aid determining correctly assessing basin evolution. The present study focuses on nonmarine deposit found within Jurassic Shuttle Meadow Formation Hartford Basin, one many rift basins formed result opening North Atlantic Ocean during Late Triassic Early Jurassic. upper 50 m formation at Plainville, Connecticut, interpreted continental composed five facies: red ripple cross-laminated muddy siltstones sandstones (Fr, Sr), massive siliciclastic mudstones (Fm), buff fine- medium-grained horizontally laminated (Sh), white disrupted calcareous shales (Fl3), rare micritic (Pm). Facies Fr, Sr, Sh, Fm an alluvial plain system ephemeral setting with bedload sheetflooding dominant mechanism, similar Channel Country drainage central Australia. In addition, preservation lateral accretion sandstone sheets (accretionary benches) indicate that was rapidly accreting. anomalous existence beds (in Fl3 Pm) SMF bedload-dominated sequence attributed mainly unique nature sediment load basin; no direct evidence input apparent. shallow lake margin or pond vegetation periodic exposure envisioned environment. intraclastic texture micrites primary relict lamination indicates early diagenetic alteration root penetration, desiccation cracks, burrowing.