Modelo Formation

{{Short description|Miocene geologic formation in southern California, United States}}

{{Infobox rockunit

| name = Modelo Formation

| image =

| caption =

| type = Formation

| age = Late Miocene, {{fossil range|13|5.5}}

| period = Miocene

| prilithology = Shale

| otherlithology =

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| region = Los Angeles County and Ventura County, California

| country = United States

| coordinates =

| unitof =Los Angeles Basin

| subunits =

| underlies =Pico Formation

| overlies =Rincon Shale

| thickness ={{convert|600|m|ft}}

| extent =Simi Hills, Santa Susana Mountains

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The Modelo Formation is a Miocene geologic formation in the Simi Hills and western Santa Susana Mountains of southern California, including under parts of Los Angeles.

It preserves fossils dating back to the Late Miocene of the Neogene period, among them a high number of fossil representatives of modern pelagic and deep-sea fish taxa (as well as some with benthic affinities), in addition to some seabirds and cetaceans. As suggested from this fauna, the sediments of the formation were likely deposited in a deepwater marine habitat at middle to upper bathyal depths within an abyssal fan, with geological changes along the San Andreas fault causing a rapid uplift during the latest Miocene, bringing these former deepwater sediments to the surface.{{Cite journal |last1=Rumelhart |first1=Peter E. |last2=Ingersoll |first2=Raymond V. |date=1997 |title=Provenance of the upper Miocene Modelo Formation and subsidence analysis of the Los Angeles basin, southern California: Implications for paleotectonic and paleogeographic reconstructions |url=https://pubs.geoscienceworld.org/gsabulletin/article/109/7/885-899/183276 |journal=Geological Society of America Bulletin |volume=109 |issue=7 |pages=885–899 |doi=10.1130/0016-7606(1997)109<0885:POTUMM>2.3.CO;2|bibcode=1997GSAB..109..885R |url-access=subscription }} It is likely partially contemporaneous with the Monterey Formation in some areas, such as the Ventura Basin.{{Cite journal |last1=Gilbert |first1=J. Clark |last2=Jobe |first2=Zane R. |date=2023-08-29 |title=Submarine-Channel Element Architecture Demonstrates Facies Heterogeneity in Both Strike and Dip Views: Miocene Modelo Formation, Lake Piru, California, USA |url=https://thesedimentaryrecord.scholasticahq.com/article/84246-submarine-channel-element-architecture-demonstrates-facies-heterogeneity-in-both-strike-and-dip-views-miocene-modelo-formation-lake-piru-california |journal=The Sedimentary Record |language=en |volume=21 |issue=1 |doi=10.2110/001c.84246|doi-access=free }}

Volcanic ash beds are known from the formation; these, along with fossil microorganisms, indicate that the formation was deposited between 13 and 5.5 million years ago.{{Citation |last1=Knott |first1=Jeffrey R. |title=Tephrochronology of the Miocene Monterey and Modelo Formations, California |date=2022-09-26 |work=Understanding the Monterey Formation and Similar Biosiliceous Units across Space and Time |pages=187–214 |editor-last=Aiello |editor-first=Ivano W. |url=https://pubs.geoscienceworld.org/gsa/books/edited-volume/2354/chapter/134302887/Tephrochronology-of-the-Miocene-Monterey-and |access-date=2024-09-23 |publisher=Geological Society of America |language=en |doi=10.1130/2022.2556(08) |isbn=978-0-8137-2556-7 |last2=Sarna-Wojcicki |first2=Andrei M. |last3=Barron |first3=John A. |last4=Wan |first4=Elmira |last5=Heizler |first5=Lynn |last6=Martinez |first6=Priscilla |editor2-last=Barron |editor2-first=John A. |editor3-last=Ravelo |editor3-first=A. Christina}}