Our "Top Picks" for geology databases are a good place to start. Use the Tabs (top of this page) for additional resources. Tips:
1) Combine your subject (fluvial systems, isotope geochemistry, mineralization, etc.) with the names of: rock units--Fountain Formation, Pierre Shale, Dakota Group; structures--Paradox Basin, Front Range, Beartooth Uplift; locations--Jefferson County, Golden quadrangle; time periods--Upper Cretaceous, Precambrian, Quaternary.
2) Some of your findings are "old"? Geology publications (field studies, observations, etc.) can still be valuable after decades.
3) Does your subject cross disciplines? Consider searching the literature of chemistry, engineering, environmental science or others.
4) Having trouble finding a specific publication? Check with a librarian--Some works (conference proceedings, field guidebooks, state documents, etc.) are quirky and can be difficult to discover.
(Big Thompson Mesa, UT. NASA Earth Observatory, 2009.)