prograde
/ˈprəʊɡreɪd
/adjective
1 Astronomy (Of planetary motion) proceeding from west to east; direct. The opposite of retrograde.While this relatively simple model will explain prograde and retrograde motion qualitatively, it fails on detail, so additional complications were added to improve the fit to reality....
- Numerous small, distant satellites in both prograde and retrograde orbits have been discovered recently.
- These are all in circular prograde orbits near Neptune's equatorial plane, and they probably formed in place.
2 Geology (Of a metamorphic change) resulting from an increase in temperature or pressure.Both thrust and normal faults initiated synchronously with Miocene prograde metamorphism and melting, and have moved episodically since then....
- These rocks display clear prograde metamorphism that peaks in granulite facies.
- The apparent critical temperature between 560 to 600°C for monazite growth at Ballachulish is broadly consistent with several previous studies of monazite in prograde metamorphic sequences.
verb [no object] Geology
(Of a coastline) advance towards the sea as a result of the accumulation of waterborne sediment: these oolites were probably deposited as part of the coastal sand-barrier complex as it prograded basinwards...
- The zone of active deltaic growth faulting (and margin-parallel maximum horizontal stress) has shifted basin-wards as the delta system has rapidly prograded across the shelf.
- Through time, the basin shrank as it filled with sediment that prograded inward along the margins, most rapidly along the Eastern Shelf.
- A slightly later phase of deglaciation occurred when the ice margin retreated north into St. George's Channel, forming the raised ice contact delta at the Screen Hills, which prograded southwards into high relative sea level.
Derivatives
progradation
- Overall the temporal progradation of nappe emplacement and high-pressure metamorphism towards the south mimics the southward retreat of the Hellenic subduction zone.
- Either allocyclic variations in fluvial discharge or the mouthward progradation of the fluvial system may explain the interbedded relationship of this facies with the cross-bedded sandstone.
- Autocyclic processes such as tidal-flat progradation or tidal-flat island progradation are also possible mechanisms for the Gibraltar cycles.
Origin
Early 20th century (as a verb): from pro-1 'forwards' + retrograde.