Opglabbeek Formation

{{Short description|Belgian geologic formation}}

{{Infobox rockunit

| name = Opglabbeek Formation

| image =

| caption =

| type =

| period = Selandian

| age = Middle to Late Paleocene (Selandian)
~{{Fossil range|61.6|59.2}}

| prilithology = clay, lignite, sand

| otherlithology =

| namedfor = Opglabbeek, Belgium

| namedby =

| region = Limburg

| country = Belgium

| coordinates = {{coord|51.08|5.73|region:BE|display=it}}

| unitof = Hesbaye Group

| subunits = Opoeteren, Eisden

| underlies = Heers Formation

| overlies = Houthem Formation

| thickness = 25-60 meters

| extent =

| area =

| map =

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}}

The Opglabbeek Formation is a geologic formation in the subsurface of the eastern part of Belgian Limburg. The heterogeneous formation consists of clay and sand that was deposited lagoonally and fluvially during the early Selandian (Middle Paleocene, about 60 million years old). The formation is named after the town of Opglabbeek in Limburg.

The Opglabbeek Formation is subdivided into two members: the Opoeteren Member (red clay with layers of lignite) and the Eisden Member (fine sand with crags).{{cite journal |last1=Laga |first1=Pieter |last2=Louwye |first2=Stephen |last3=Geets |first3=Stéphane |title=Paleogene and Neogene lithostratigrafic units (Belgium) |journal=Geologica Belgica |date=2001 |volume=4 |pages=136, 138 |url=https://popups.uliege.be/1374-8505/index.php?id=1954 |access-date=April 28, 2022}}

The Opglabbeek Formation's thickness ranges between {{convert|25|m|ft}} and {{convert|60|m|ft}}, reaching its greatest thickness as it abuts the Roer Valley Graben.{{cite journal |last1=Deckers |first1=Jef |last2=Matthijs |first2=Johan |title=A late Danian change in deformation style in the south-eastern part of the Campine Basin |journal=Geologica Belgica |date=January 2014 |volume=17 |issue=3–4 |page=239 |url=https://www.researchgate.net/publication/283444476 |access-date=28 April 2022}} It lies stratigraphically on top of the Houthem Formation (early Paleocene calcareous sandstone). It is the lateral equivalent of the Hainin Formation.{{cite journal |last1=Steurbaut |first1=E |title=High-resolution holostratigraphy of Middle Paleocene to Early Eocene strata in Belgium and adjacent areas |journal=Palaeontographica A |date=1998 |volume=247 |issue=5–6 |pages=91–156 |doi=10.1127/pala/247/1998/91 |s2cid=133583770 |url=https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1575545&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US |access-date=28 April 2022|url-access=subscription }} On top of it lies the Heers Formation (Middle Paleocene sands and marls). The Opglabbeek Formation is part of the Hesbaye Group and can be correlated with parts of the Landen Formation of adjacent areas in the southern Netherlands.