Photo 1 Photo 2 Photo 3 Photo 4 Photo 5 Photo 6
Peninsular Ranges Batholith  ·  Coordinates redacted
The Solstice
Shrine Study
A documented archaeoastronomical site featuring upright lithic monuments aligned to winter solstice sunrise, associated milling features, and evidence of deliberate geological material selection. Witnessed by U.S. Forest Service archaeologists, December 21, 2025.
USFS documented Alignment confirmed Location protected
Alignment
Winter solstice sunrise — December 21, 2025
Alignment confirmed in the field by two U.S. Forest Service archaeologists present as witnesses on the winter solstice, December 21, 2025. Event recorded via photograph and video.
Event summary

On December 21, 2025, the winter solstice sunrise was observed and recorded aligning precisely through the gap formed by the two upright lithic slabs. The alignment had been anticipated from the gap geometry and horizon azimuth prior to the event. Two U.S. Forest Service archaeologists were present as witnesses. The precision of the alignment, where the sun rises centered in the gap at the moment of solstice, is consistent with intentional orientation of the monument.

WITNESSES
2 USFS Archaeologists
DATE
December 21, 2025
MEDIA
Photo + video
AZIMUTH
~120° SE
Solstice alignment
Solstice sunrise through the gap — Dec 21 2025
Alignment video
multiple angles
MP4
Rising sun — multiple angles — Dec 21 2025
Monument
Upright lithic slabs — shim stones — platform base
Description

Two tall monzogranite clasts stand upright on a tonalite bedrock platform at an elevated ridge position with an open eastern horizon. The upright monzogranites are medium- to coarse-grained and consist of biotite leucomonzogranite, leucogranodiorite, and syenogranite which are more resistant to weathering than any other granitoid. Small shim stones are positioned at the base of both uprights, behind the left clast and in front of the right, stabilizing their position in a manner inconsistent with natural emplacement. The gap between the two uprights frames the winter solstice sunrise precisely.

Front view of monument
Front view — pre-sunrise
Side view from north
Side view — north facing south
Monument with USFS archaeologist for scale
USFS archaeologist at base — scale reference — Dec 21 2025
Structural observations
Two upright monzogranite clasts forming a precise gap oriented to winter solstice sunrise
Confirmed — USFS witnessed
Shim stones present at base of both uprights — inconsistent with natural emplacement
Confirmed — photographed
Uprights seated on flat monzogranite platform slab above tonalite bedrock — possible intentional leveling surface
Probable — under review
Smaller boulder visible behind left upright — possible back-shim or marker stone
Noted — pending analysis
Geological analysis
Peninsular Ranges Batholith — dual-lithology classification
Uprights & slab platform
Western PRB  ·  Monzogranite
The westernmost Corte Madera magma chambers were shallow and vented to the surface. The Corte Madera Monzogranite consists of medium- to coarse-grained biotite leucomonzogranite, leucogranodiorite, and syenogranite. Because of the unit’s low color index (1 to 11), outcrops weather white with a distinct light pinkish-orange hue.
Implies deliberate selection as the Corte Madera Monzogranite, per the USGS, is more resistant to weathering than any other granitoid.
Base bedrock
Western PRB  ·  Tonalite / Granodiorite
The most abundant rock types of the tonalite of Las Bancas are medium-grained, equigranular hypersthene-biotite tonalite, quartz diorite, and granodiorite, but include lesser diorite, quartz monzodiorite, and quartz norite. Potassium feldspar oikocrysts ranging from 0 to 15% of the rocks are especially present in eastern Las Bancas plutons. Locally, tonalite displays cumulate layering and contains scarce, small ovoid basaltic inclusions.
Structural stability ideal as foundation.
Shim stones
Eastern PRB  ·  Matching uprights
Smaller monzogranite boulder fragments. Positioned at base of both uprights. Material is compositionally identical to the upright slabs above them — consistent with deliberate sourcing from the same rock unit.
Same lithology as uprights — consistent with deliberate sourcing.
Mano handstones
Lithology TBD  ·  Formal analysis pending
Surface-discarded mano handstone with worn facies. Associated with potential bedrock mortars and metates in the surrounding complex. USFS recording in progress.
Confirms subsistence and/or ritual activity.
USGS bedrock comparison
USGS — monument rock type comparison
USGS Corte Madera Monzogranite report
USGS — Corte Madera Monzogranite
USGS Tonalite of Las Blancas report
USGS — Tonalite of Las Blancas
Surrounding complex
Associated features within the broader site area
Site context

The monument does not stand in isolation. The surrounding landscape contains multiple associated features distributed across several hundred meters, collectively suggesting a multi-functional, repeatedly visited site over an extended time period. Features include fire-darkened boulder depressions to the north, tafoni erosion features in the surrounding area with possible anthropomorphic modification for cultural use, and mano handstones recovered approximately 800 meters to the south — indicating the broader complex extends well beyond the monument itself.

Fire-darkened boulder depressions
Fire-darkened boulder depressions — approx. 60–70m north
Mano handstone
Mano handstone — approx. 800m south of monument
Bedrock milling
Possible bedrock milling, cupules — approx 800m southwest of monument
Tafoni depressions
Tafoni depressions in bedrock — platform area
Documented complex features
Fire-darkened boulder depressions — approximately 60–70 meters north of the monument
Recorded — Dec 21 2025
Mano handstone — discarded grinding stone recovered approximately 800 meters south
Recorded — USFS documentation in progress
Tafoni depressions in bedrock — weathering cavities in the platform area
Recorded — natural vs. modified status under review
Potential bedrock milling features (mortars / metates) in surrounding area
Noted — formal recording pending
References
Primary sources, comparative studies, and ethnographic literature
Request research access
Full media, GPS coordinates, and field notes — qualified researchers only
Exact location, GPS metadata, and unredacted imagery are withheld to protect site integrity and pending tribal consultation. Access is considered for archaeologists, tribal historic preservation officers, academic researchers, and credentialed institutions. All requests are reviewed personally.

For general inquiries please contact: sdbanks619 [at] gmail [dot] com
Research timeline
Late 2024
Initial discovery
Site identified during field reconnaissance. Upright lithic forms, shim stones, and solstice orientation hypothesis formed from gap geometry and horizon position.
December 21, 2025
Solstice verification — USFS field visit
Guided site visit with two U.S. Forest Service archaeologists. Winter solstice sunrise alignment confirmed and recorded. Mano handstones and bedrock milling features documented. Tribal consultation initiated.
2025–2026
USFS formal site recording
California site number assignment in progress. Photographic archive, geologic analysis, and field notes being compiled for the record.
Pending
Tribal consultation completion
Formal consultation with relevant Kumeyaay and/or Luiseño tribal historic preservation officers. Their findings will shape how and whether full site data is published.
Pending
Academic publication
Full research paper and unredacted media archive to be released following USFS recording and tribal consultation. Targeted at peer-reviewed archaeoastronomy or California archaeology journals.